The rapid development of electric vehicles and portable energy storage systems demands improvements in the energy density and cost-effectiveness of lithium-ion batteries,a domain in which Lithium-rich layered cathode(...The rapid development of electric vehicles and portable energy storage systems demands improvements in the energy density and cost-effectiveness of lithium-ion batteries,a domain in which Lithium-rich layered cathode(LLO)materials inherently excel.However,these materials face practical challenges,such as low initial Coulombic efficiency,inferior cycle/rate performance,and voltage decline during cycling,which limit practical application.Our study introduces a surface multi-component integration strategy that incorporates oxygen vacancies into the pristine LLO material Li1.2Mn_(0.6)Ni_(0.2)O_(2).This process involves a brief citric acid treatment followed by calcination,aiming to explore rate-dependent degradation behavior.The induced surface oxygen vacancies can reduce surface oxygen partial pressure and diminish the generation of O_(2)and other highly reactive oxygen species on the surface,thereby facilitating the activation of Li ions trapped in tetrahedral sites while overcoming transport barriers.Additionally,the formation of a spinel-like phase with 3D Li+diffusion channels significantly improves Li^(+)diffusion kinetics and stabilizes the surface structure.The optimally modified sample boasts a discharge capacity of 299.5 mA h g^(-1)at a 0.1 C and 251.6 mA h g^(-1)at a 1 C during the initial activation cycle,with an impressive capacity of 222.1 mA h g^(-1)at a 5 C.Most notably,it retained nearly 70%of its capacity after 300 cycles at this elevated rate.This straightforward,effective,and highly viable modification strategy provides a crucial resolution for overcoming challenges associated with LLO materials,making them more suitable for practical application.展开更多
According to surface morphology,microhardness,X-ray diffraction,and static contact angle experiments,the changes in the surface integrity and corrosion resistance of 6061-T6 aluminum alloy after ultrasonic shot peenin...According to surface morphology,microhardness,X-ray diffraction,and static contact angle experiments,the changes in the surface integrity and corrosion resistance of 6061-T6 aluminum alloy after ultrasonic shot peening(USP)were investigated.Results show that the grain size of the material surface is reduced by 43%,the residual compressive stress has an increasing trend,the roughness and hardness are increased by approximately 211.1%and 35%,respectively.And the static contact angle is increased at first,followed by a slight decrease.Weighing,scanning electron microscope,and energy dispersive spectrometer were used to study the samples after a cyclic corrosion test.Results show that USP reduces the corrosion rate by 41.2%.A model of surface corrosion mechanism of USP is developed,and the mechanism of USP to improve the corrosion resistance of materials is discussed.The introduction of compressive residual stresses,grain refinement,increased grain boundaries,increased hardness,and increased static contact angle are the main factors related to the improvement of corrosion resistance in most materials,while increased roughness tends to weaken surface corrosion resistance.展开更多
Machine Hammer Peening(MHP)is an emergent treatment that induces high compressive Residual Stresses(RS)which can enhance the in-service performance of components.This paper studies the use of small diameter MHP tools ...Machine Hammer Peening(MHP)is an emergent treatment that induces high compressive Residual Stresses(RS)which can enhance the in-service performance of components.This paper studies the use of small diameter MHP tools to improve the Surface Integrity(SI)of the nickel-based alloy Inconel 718 used in critical aero-engine components.Complementarily,the relaxation of RS is analyzed by in-situ annealing tests at in-service temperature combined with X-ray diffraction measurement.For this purpose,age hardened Inconel 718 discs were turned as reference condition,and then a pneumatic MHP tool was used under different conditions:two tool diameters(4 mm and 12 mm),feed rates(2.5 m/min and 5.0 m/min)and stepover distances(0.07 mm and 0.35 mm).Subsequently,surface topography characterization,RS measurements,nanoindentation tests,and microstructural observations were conducted.The in-situ annealing tests were done in the X-ray diffractometer at 550°C for exposure periods from 0 to 20 h.The results demonstrate that 4 mm diameter tools generate smooth surfaces and induce significant compressive RS within a0.5 mm thick layer.Residual stresses are relaxed,but they remain compressive even after a long thermal exposure.The microstructure of the surface layer(<10–15μm)was affected by the preceding turning operation,but importantly,MHP did not induce additional damage.展开更多
To address problems in surface integrity and machining allowance distribution during combined electric arc-mechanical milling,this paper takes TC4 as the research object,examines the influence of electric arc milling(...To address problems in surface integrity and machining allowance distribution during combined electric arc-mechanical milling,this paper takes TC4 as the research object,examines the influence of electric arc milling(EAM)depth on recast layer thickness and surface roughness,alongside an analysis of the recast layer’s organization characteristics and sur-face morphology.A comparative evaluation of cutting forces,surface roughness,and surface hardening is conducted between combined milling and conventional mechanical milling.Key findings reveal that electric arc machining produces a recast layer with a hardness of 313.21 HV.As the EAM depth increases,the localized recast layer thickness and peak-to-valley(PV)differ-ences also rise.To ensure effective surface defect removal,the machining allowance for subsequent mechanical milling must exceed the combined thickness of the recast layer and the PV difference.Under identical parameters,combined milling yields higher surface roughness(0.584μm)and greater surface hardening(10.4%)compared to mechanical milling alone,alongside an 18.716 N increase in cutting force.Response surface methodology(RSM)analysis identifies feed per tooth as the most significant factor affecting surface roughness,followed by spindle speed,with milling depth having the least influence.展开更多
Machined surface integrity of workpieces in harsh environments has a remarkable influence on their performance.However,the complexity of the new type of machining hinders a comprehensive understanding of machined surf...Machined surface integrity of workpieces in harsh environments has a remarkable influence on their performance.However,the complexity of the new type of machining hinders a comprehensive understanding of machined surface integrity and its formation mechanism,thereby limiting the study of component performance.With increasing demands for high-quality machined workpieces in aerospace industry applications,researchers from academia and industry are increasingly focusing on post-machining surface characterization.The profile grinding test was conducted on a novel single-crystal superalloy to simulate the formation of blade tenons,and the obtained tenons were characterized for surface integrity elements under various operating conditions.Results revealed that ultrasonic vibration-assisted grinding(UVAG)led to multiple superpositions of abrasive grain trajectories,causing reduced surface roughness(an average reduction of approximately29.6%)compared with conventional grinding.After examining the subsurface layer of UVAG using transmission electron microscopy,the results revealed that the single-crystal tenon grinding subsurface layer exhibited a gradient evolution from the near-surface to the substrate.This evolution was characterized by an equiaxed nanocrystalline layer measuring 0.34μm,followed by a submicrocrystalline grain-forming zone spanning 0.6μm and finally,a constituent phase-twisted dis-torted deformation zone over 0.62μm.Under normal grinding conditions,the tenon exhibited low surface hardening(not exceeding 15%),and residual compressive stresses were observed on its surface.In cases where grinding burns occurred,a white layer appeared on the tenon's surface,which demonstrated varying thicknesses along the teeth from top to root due to thermal-force-structural coupling effects.Additionally,these burns introduced residual tensile stresses on the tenon's surface,potentially substantially affecting its fatigue life.This paper enhances our understanding of UVAG processes and establishes a foundation for their application in manufacturing singlecrystal turbine blades for next-generation aero-turbine engines.展开更多
Gamma titanium-aluminum(γ-TiAl)intermetallic compounds are increasingly used in manufacturing key hot-end components(e.g.,blade tenon)in aero engines due to their high specific strength and lightweight properties.Cre...Gamma titanium-aluminum(γ-TiAl)intermetallic compounds are increasingly used in manufacturing key hot-end components(e.g.,blade tenon)in aero engines due to their high specific strength and lightweight properties.Creep feed profile grinding(CFPG)as a crucial precision process that is applied to produce the final profile of the blade tenon.However,sudden surface burns and microcracks of machined c-TiAl blade tenon often occur because of its low plasticity and high strength during grinding processes,leading to poor surface integrity.In this work,CFPG experiments based on the profile characteristics ofγ-TiAl blade tenon were performed and an associated undeformed chip thickness model considering grain–workpiece contact condition was established to explore the evolution of the surface integrity.Subsequently,the surface integrity was analyzed at different positions of the blade tenon in terms of surface roughness and morphology,metallographic structure,microhardness,and residual stress.Results show that the profile characteristics of blade tenon have a significant influence on machined surface integrity because of the thermomechanical effect at various detecting positions.The residual stress was established based on the undeformed chip thickness model considering the profile structure,with a prediction error of 10%–15%.The thermomechanical effect is more obvious at the bottom area,where the surface roughness,work hardening degree,and subsurface plastic deformation range are the largest,while the values at the bevel area are the smallest.Based on the undeformed chip thickness model,a residual stress finite element simulation was conducted by employing thermomechanical coupled effects.In addition,the error between the simulation and the experiment was between 10%–15%.Strain and strain rate equations were established through the relationship between material displacement and depth.The average strain and strain rate of the ground surface when ap is 1.0 mm are 18.8%and 33.2%larger than when ap is 0.5 mm,respectively.This study deepens the understanding of surface integrity under the influence of CFPGγ-TiAl and provides a practical reference and theoretical basis for realizing high-quality profile grinding of other complex parts.展开更多
Current Ti-based orthopedic implants often suffer from fatigue damage,therefore shortening their service lifespan.To solve this issue,in this study,mechanically polished Ti-6Al-7Nb(P-Ti6Al7Nb)was subjected to surface ...Current Ti-based orthopedic implants often suffer from fatigue damage,therefore shortening their service lifespan.To solve this issue,in this study,mechanically polished Ti-6Al-7Nb(P-Ti6Al7Nb)was subjected to surface mechanical attrition treatment(SMAT).Effects of various SMAT process parameters,including ball diameter and treatment duration,on the surface integrity of P-Ti6Al7Nb were investigated,specifically in terms of surface quality,surface nanocrystalline layer,and residual stress.Subsequently,the microstructure,in-depth residual stress and microhardness distributions,surface roughness,and fatigue behavior in simulated body fluids of optimally SMATed Ti-6Al-7Nb(S-Ti6Al7Nb)were examined and compared to those of P-Ti6Al7Nb.Results showed that based on the experimental conditions established in the present research,the optimal parameters were determined to be a 3 mm ball diameter and a 15 min treatment duration,which resulted in excellent surface integrity;S-Ti6Al7Nb showed a 300μm-thick gradient nanostructured layer comprising the thickest nanocrystalline layer of about 20μm,a 1000μm-deep residual compressive stress field with the maximum surface residual compressive stress,and a microconcave topography but free of any defects or cracks.The microstructural evolution mechanism was also elucidated,revealing that the combination of multidirectional primary and secondary twins’intersections and twin-dislocation interactions contributed to grain refinement.Compared to P-Ti6Al7Nb,S-Ti6Al7Nb exhibited a 40%improvement in fatigue strength,owing to synergistic effects of the gradient nanostructured layer,surface work hardening,high amplitude of residual compressive stress,and improved surface integrity.These factors effectively prevented the initiation of fatigue crack at the surface and shifted it to the sublayer,and inhibited the subsequent crack propagation.展开更多
Submerged abrasive waterjet peening(SAWJP)is an effective anti-fatigue manufacturing technology that is widely used to strengthen aeroengine components.This study investigated the correlation of SAWJP process paramete...Submerged abrasive waterjet peening(SAWJP)is an effective anti-fatigue manufacturing technology that is widely used to strengthen aeroengine components.This study investigated the correlation of SAWJP process parameters on surface integrity and fatigue life of titanium alloy TA19.SAWJP with different water pressures and standoff distances(SoDs)was conducted on the TA19 specimens.The surface integrity of the specimens before and after SAWJP with different process parameters was experimentally studied,including microstructure,surface roughness,microhardness,and compressive residual stress(CRS).Finally,fatigue tests of the specimens before and after SAWJP treatment with different process parameters were carried out at room temperature.The results highlighted that the fatigue life of the TA19 specimen can be increased by 5.46,5.98,and 6.28 times under relatively optimal process parameters,which is mainly due to the improved surface integrity of the specimen after SAWJP treatment.However,the fatigue life of specimens treated with improper process parameters is decreased by 0.55 to 0.69 times owing to the terrible surface roughness caused by the material erosion.This work verifies that SAWJP can effectively improve the surface integrity and fatigue life of workpieces,and reveals the relationship between process parameters,surface integrity,and fatigue life,which provides support for the promotion of SAWJP in the manufacturing fields.展开更多
Advanced hole-making process is of great importance to enhance the fatigue performance of Al-Li alloy part in aviation industry.Ultrasonic peening drilling(UPD),in which an ultrasonic transversal vibration is applied ...Advanced hole-making process is of great importance to enhance the fatigue performance of Al-Li alloy part in aviation industry.Ultrasonic peening drilling(UPD),in which an ultrasonic transversal vibration is applied to the cutting tools,is a recently proposed hole-making method that integrates precision-machining and surface strengthening by single-shot operation.In the study,kinematics,material removal mechanism and strengthening mechanism for UPD of Al-Li alloy by helical fluted reamers are analyzed.The effect of transversal vibration on the cutting performance and surface integrity is studied through comparative experiments between UPD and conventional drilling(CD)of Al-Li alloy holes.The experimental results show that UPD exhibits superior cutting performance with a maximum reduction of 52.6%in thrust force and 52.3%in torque,respectively,compared to CD.Moreover,narrower dimensional tolerance is obtained in UPD due to the reduced transversal force and improved machining stability.Additionally,deeper plastic deformation,higher surface microhardness and residual compressive stress of machined holes are obtained by UPD.The electron back-scattered diffraction(EBSD)analysis confirms that deeper machined affect area and grain refinement are realized in UPD.Therefore,the results indicate that UPD is a feasible method for achieving high-precision and strengthened holes for Al-Li alloy.展开更多
Fatigue properties are crucial for critical aero-engine components in extreme serviceenvironments,which are significantly affected by surface integrity(SI)indexes(especially surface topography,residual stressσ_(res),...Fatigue properties are crucial for critical aero-engine components in extreme serviceenvironments,which are significantly affected by surface integrity(SI)indexes(especially surface topography,residual stressσ_(res),and microhardness)after machining processes.Normal-direction ultrasonic vibration-assisted face grinding(ND-UVAFG)has advantages in improving the machinability of Inconel 718,but there is a competitive relationship between higher compressiveσ_(res)and higher surface roughness R_(a)in affecting fatigue strength.The lack of a quantitative relationship between multiple SI indexes and fatigue strength makes theindeterminacy of a regulatory strategy for improving fatigue properties.In this work,a model of fatigue strength(σ_f)_(sur)considering multiple SI indexes was developed.Then,high-cycle fatigue tests were carried out on Inconel 718 samples with different SI characteristics,and the influence of ND-UVAFG process parameters on SI was analyzed.Based on SI indexes data,the(σ_f)_(sur)distribution in the grinding surface layer for ND-UVAFG Inconel 718 samples was determined using the developed model,and then the fatigue crack initiation(FCI)sites were furtherpredicted.The predicted FCI sites corresponded well with the experimental results,therebyverifying this model.A strategy for improving the fatigue life was proposed in this work,which was to transfer the fatigue source from the machined surface to the bulk material by controlling the SI indexes.Finally,a critical condition of SI indexes that FCI sites appeared on the surface or in bulk material was given by fitting the predicted results.According to the critical condition,an SI field where FCI sites appeared in the bulk material could be obtained.In this field,thefatigue life of Inconel 718 samples could be improved by approximately 140%.展开更多
The technique of creep feed grinding is most suitable for geometrical shaping, and therefore has been expected to improve effectively material removal rate and surface quality of components with complex profile. This ...The technique of creep feed grinding is most suitable for geometrical shaping, and therefore has been expected to improve effectively material removal rate and surface quality of components with complex profile. This article studies experimentally the effects of process parameters （i.e. wheel speed, workpiece speed and depth of cut） on the grindability and surface integrity of cast nickel-based superalloys, i.e. K424, during creep feed grinding with brazed cubic boron nitride （CBN） abrasive wheels. Some important factors, such as grinding force and temperature, specific grinding energy, size stability, surface topography, microhardhess and microstructure alteration of the sub-surface, residual stresses, are investigated in detail. The results show that during creep feed grinding with brazed CBN wheels, low grinding temperature at about 100 ℃ is obtained though the specific grinding energy of nickel-based superalloys is high up to 200-300 J/mm^3. A combination of wheel speed 22.5 m/s, workpiece speed 0.1 m/min, depth of cut 0.2 mm accomplishes the straight grooves with the expected dimensional accuracy. Moreover, the compressive residual stresses are formed in the bum-free and crack-free ground surface.展开更多
Titanium alloy tenon is creep feed ground with monolayer brazed cubic boron nitride （CBN） shaped wheels. The dimension accuracy of the tenon is assessed and the results indicate that it completely meets the requirem...Titanium alloy tenon is creep feed ground with monolayer brazed cubic boron nitride （CBN） shaped wheels. The dimension accuracy of the tenon is assessed and the results indicate that it completely meets the requirement of blade tenon of aero-engine. Residual stresses, surface roughness, microstructure and microhardness are measured on ground surfaces of the specimen, which are all compared with that ground with vitrified CBN wheels. Under all the circumstances, compressive residual stress is obtained and the depth of the machining affected zone is found to be less than 40 μm. No phase transformation is observed at depths of up to 100 lain below the surface, though plastic deformation is visible in the process of grain refinement. The residual stress and microhardness of specimens ground with brazed CBN wheels are observed to be lower than those ground with vitrified ones. The arithmetic mean roughness （Ra） values obtained are all below 0.8μm.展开更多
Surface integrity of a new damage-tolerant titanium alloy （TC21）, including surface roughness, microhardness and metallurgical structure is investigated when normal and high speed milling are used at different tool ...Surface integrity of a new damage-tolerant titanium alloy （TC21）, including surface roughness, microhardness and metallurgical structure is investigated when normal and high speed milling are used at different tool wear status. Results show that good surface integrity of TC21 can be obtained in high speed milling. In addition, even in acutely worn stages, there is no so-called serious hardening layer （or white layer） according to the studies on microhardness and metallurgical structure.展开更多
To evaluate the new designed cutting tools for high-efficiency milling of the hardened die steel SKD11,surface integrities of millers with different geometric structures are analyzed, considering the surface roughness...To evaluate the new designed cutting tools for high-efficiency milling of the hardened die steel SKD11,surface integrities of millers with different geometric structures are analyzed, considering the surface roughness, micrograph of chips, surface microhardness, residual stress and metallurgical texture of the surface layer. The in fluences of geometric characteristics of different cutting tools and their wear characteristics on the surface integrity are studied. Results show that the milling tool with rake angle; 5 of the hardened diesteel. The generation of saw-tooth chips is depressed when a reasonable positive rake angle is selected. And the compressive residual stress is induced on the machined surface in milling the hardened die steel. The occurrence of surface softening is postponed by increasing the clearance angle and reducing the tool flank wear.展开更多
Silicon carbide(SiC)ceramics are extensively utilized in aerospace,national defense,and petrochemical industries due to their superior physical and chemical properties.The processing of bulk SiC ceramics necessitates ...Silicon carbide(SiC)ceramics are extensively utilized in aerospace,national defense,and petrochemical industries due to their superior physical and chemical properties.The processing of bulk SiC ceramics necessitates precise and efficient grinding techniques to produce components with satisfactory functionality.However,the inherent high hardness and brittleness of SiC ceramics present significant challenges during grinding,leading to severe brittle fracture and tool wear that compromise both surface integrity and production efficiency.Although ductile-regime grinding of SiC ceramics can be achieved by enhancing machine tool accuracy and stiffness while optimizing wheel performance alongside appropriate selection of process parameters,a comprehensive summary of the mechanisms underlying damage evolution during grinding is lacking,and a mature grinding process for SiC ceramics has yet to be developed.To bridge this gap,the sintering technologies,mechanical properties,and microstructures of SiC ceramics were briefly covered.The grinding-induced damage mechanism and low-damage grinding technologies of SiC ceramics were summarized.The fundamental science underlying the ductile deformation and removal mechanisms of brittle solids was emphasized.Additionally,attention was directed towards the critical role of hybrid energy field grinding in minimizing brittle damages and promoting removal efficiency.This review not only elucidates the intrinsic interactions between the work material and abrasives,but also offers valuable insights for optimizing the grinding processes of brittle solids.展开更多
Submerged Abrasive Waterjet Peening(SAWJP)shows great application potential in augmenting the fatigue properties of metallic parts.Thus,the present work aims to investigate the influence of SAWJP on the Surface Integr...Submerged Abrasive Waterjet Peening(SAWJP)shows great application potential in augmenting the fatigue properties of metallic parts.Thus,the present work aims to investigate the influence of SAWJP on the Surface Integrity(SI)and Fretting Fatigue(FF)properties of Inconel 718(IN718)superalloy and illustrate the microstructural evolution,FF life improvement,and fretting wear mechanism.First,the SI of the IN718 specimen was examined following treatment via SAWJP.Results showed that the specimen subjected to SAWJP formed a total plastic deformation layer of 56μm.The maximum microhardness and Compressive Residual Stress(CRS)measured across the depth of the SAWJP-treated specimens exhibited an increase in values ranging between 522 HV and 541 HV and 1171–1380 MPa,respectively.The FF test results of the specimen before and after SAWJP treatment at ambient temperatures indicated that the FF life of the SAWJP-treated specimen surpassed that of the as-received specimen by a factor of 2.81.The examination of the FF fracture,contact surface,and crack propagation behavior revealed the crucial factors contributing to the enhanced FF resistance of the IN718 specimen,including the gradient nanostructure characterized by ultra-refined grains,substantial CRS,and elevated microhardness,which were all induced by the SAWJP treatment.展开更多
Ultrasonic elliptical vibration cutting(UEVC)with clockwise elliptical vibration has made notable achievements in precision machining;however,its critical cutting speed limits its application to low-speed machining ta...Ultrasonic elliptical vibration cutting(UEVC)with clockwise elliptical vibration has made notable achievements in precision machining;however,its critical cutting speed limits its application to low-speed machining tasks.Meanwhile,rotary ultrasonic elliptical machining(RUEM)with clockwise elliptical vibration has been validated as an effective high-speed cutting technology.Unfortunately,conventional RUEM leads to increased surface roughness.To address this issue and enhance machining quality,we propose a novel RUEM method employing an anticlockwise vibration direction,called anticlockwise rotary ultrasonic elliptical machining(ARUEM).The mechanisms of surface formation and subsurface strengthening for ARUEM are analyzed.Experimental validations were performed on Ti-6Al-4V alloy,revealing that ARUEM achieved substantially lower ridge heights and up to a 50%reduction in surface roughness compared to conventional RUEM.Additionally,relative to conventional milling,ARUEM resulted in up to 122.6%thicker plastic deformation layers,53.4%higher surface residual compressive stress,and 19.3%greater surface micro-hardness.This study showcases a promising method for high-performance milling of Ti-6Al-4V,offers new insights into RUEM by examining the influence of vibration direction,and enhances understanding of surface formation and subsurface strengthening in the ARUEM method.展开更多
Titanium alloys are widely used in aeronautics that demand a good combination of high strength, good corrosion resistance and low mass. The mechanical properties lead to challenges in machining operations such as high...Titanium alloys are widely used in aeronautics that demand a good combination of high strength, good corrosion resistance and low mass. The mechanical properties lead to challenges in machining operations such as high process temperature as well as rapidly increasing tool wear. The conventional tool materials are not able to maintain their hardness and other mechanical prop- erties at higher cutting temperatures encountered in high speed machining. In this work, the new material tools, which are poly- crystalline diamond （PCD） and polycrystalline cubic boron nitride （PCBN） tools, are used in high-speed milling of Ti-6.5AI-2Zr-IMo-IV （TA15） alloy. The performance and wear mechanism of the tools are investigated. Compared to PCBN tool, PCD tool has a much longer tool life, especially at higher cutting speeds. Analyses based on the SEM and EDX suggest that attrition, adhesion and diffusion are the main wear mechanisms of PCD and PCBN tools in high-speed milling of TA 15. Oxida- tion wear is also observed at PCBN tool/workpiece interface. Roughness, defects, micro-hardness and microstructure of the ma- chined surface are investigated. The recorded surface roughness values with PCD/PCBN tools are bellow 0.3 μm at initial and steady cutting stage. Micro-hardness analysis shows that the machined surface hardening depth with PCD and PCBN tools is small. There is no evidence of sub-surface defects with PCD and PCBN tools. It is concluded that for TA15 alloy, high-speed milling can be carried out with PCD/PCBN tools.展开更多
Surface topography of superalloy GH4169 workpieces machined by milling and grinding is different significantly. Meanwhile, surface roughness, as one of the main indicators of machined surface integrity, has a great in...Surface topography of superalloy GH4169 workpieces machined by milling and grinding is different significantly. Meanwhile, surface roughness, as one of the main indicators of machined surface integrity, has a great influence on the fatigue behavior of workpieces. Based on analyzing the formation mechanism and characteristics of surface roughness utilizing different machining processes and parameters, the machined surface roughness curve can be decoupled into two parts utilizing frequency spectrum analysis, which are kinematic surface roughness curve and stochastic surface roughness curve. The kinematic surface roughness curve is influenced by machining process,parameters, geometry of the cutting tool or wheel, the maximum height of which is expressed as Rz＇.By subtracting the kinematic part from the measurement curve, the stochastic surface roughness curve and its maximum height Rz＂ can be obtained, which is influenced by the defects of cutting tool edge or abrasive grains, built-up edges（BUE）, cracks, high frequency vibration and so on. On the other hand, the results of decoupling analysis of surface roughness curves indicate that Raand Rz values of milling GH4169 are 2–5 times and 1–3 times as high as those of grinding, while Rz＂ value of milling is 13.85%–37.7% as high as that of grinding. According to the results of fatigue life tests of specimens machined by milling and grinding, it can be concluded that fatigue behavior of GH4169 decreases with the increase of Rz＂monotonically, even utilizing different machining processes.展开更多
The integral impeller and blisk of an aero-engine are high performance parts with complex structure and made of difficult-to-cut materials. The blade surfaces of the integral impeller and blisk are functional surfaces...The integral impeller and blisk of an aero-engine are high performance parts with complex structure and made of difficult-to-cut materials. The blade surfaces of the integral impeller and blisk are functional surfaces for power transmission, and their surface integrity has signif- icant effects on the aerodynamic efficiency and service life of an aero-engine. Thus, it is indispensable to finish and strengthen the blades before use. This paper presents a comprehensive literature review of studies on finishing and strengthening technologies for the impeller and blisk of aero-engines. The review includes independent and inte- grated finishing and strengthening technologies and dis- cusses advanced rotational abrasive flow machining with back-pressure used for finishing the integral impeller and blisk. A brief assessment of future research problems and directions is also presented.展开更多
基金supported by the National Key R&D Program of China(2021YFB2401800)the National Natural Science Foundation of China(21875022,22179008)+4 种基金the Yibin‘Jie Bang Gua Shuai’(2022JB004)the support from the Beijing Nova Program(20230484241)the support from the Postdoctoral Fellowship Program of CPSF(GZB20230931)the support from the 4B7B beam line of Beijing Synchrotron Radiation Facility(2021-BEPC-PT-005924,2021-BEPC-PT-005967)BL08U1A beam line of Shanghai Synchrotron Radiation Facility(2021-SSRF-PT-017710)。
文摘The rapid development of electric vehicles and portable energy storage systems demands improvements in the energy density and cost-effectiveness of lithium-ion batteries,a domain in which Lithium-rich layered cathode(LLO)materials inherently excel.However,these materials face practical challenges,such as low initial Coulombic efficiency,inferior cycle/rate performance,and voltage decline during cycling,which limit practical application.Our study introduces a surface multi-component integration strategy that incorporates oxygen vacancies into the pristine LLO material Li1.2Mn_(0.6)Ni_(0.2)O_(2).This process involves a brief citric acid treatment followed by calcination,aiming to explore rate-dependent degradation behavior.The induced surface oxygen vacancies can reduce surface oxygen partial pressure and diminish the generation of O_(2)and other highly reactive oxygen species on the surface,thereby facilitating the activation of Li ions trapped in tetrahedral sites while overcoming transport barriers.Additionally,the formation of a spinel-like phase with 3D Li+diffusion channels significantly improves Li^(+)diffusion kinetics and stabilizes the surface structure.The optimally modified sample boasts a discharge capacity of 299.5 mA h g^(-1)at a 0.1 C and 251.6 mA h g^(-1)at a 1 C during the initial activation cycle,with an impressive capacity of 222.1 mA h g^(-1)at a 5 C.Most notably,it retained nearly 70%of its capacity after 300 cycles at this elevated rate.This straightforward,effective,and highly viable modification strategy provides a crucial resolution for overcoming challenges associated with LLO materials,making them more suitable for practical application.
基金Introduction of Talent Research Start-up Fund of Anhui University of Science and Technology(2022yjrc35)Colleges and Universities Excellent Young Talents Domestic Visit Research Project of Anhui Province(gxgnfx2022006)。
文摘According to surface morphology,microhardness,X-ray diffraction,and static contact angle experiments,the changes in the surface integrity and corrosion resistance of 6061-T6 aluminum alloy after ultrasonic shot peening(USP)were investigated.Results show that the grain size of the material surface is reduced by 43%,the residual compressive stress has an increasing trend,the roughness and hardness are increased by approximately 211.1%and 35%,respectively.And the static contact angle is increased at first,followed by a slight decrease.Weighing,scanning electron microscope,and energy dispersive spectrometer were used to study the samples after a cyclic corrosion test.Results show that USP reduces the corrosion rate by 41.2%.A model of surface corrosion mechanism of USP is developed,and the mechanism of USP to improve the corrosion resistance of materials is discussed.The introduction of compressive residual stresses,grain refinement,increased grain boundaries,increased hardness,and increased static contact angle are the main factors related to the improvement of corrosion resistance in most materials,while increased roughness tends to weaken surface corrosion resistance.
基金the financial support given by EPSRC to the Grant LOFAMO(No.EP/X023281/1)the Basque Government for the financial support given from Elkartek Program to the Project FRONTIERS 2022—Superficies Multifuncionales en la Frontera del Conocimiento(No.KK2022/00109)。
文摘Machine Hammer Peening(MHP)is an emergent treatment that induces high compressive Residual Stresses(RS)which can enhance the in-service performance of components.This paper studies the use of small diameter MHP tools to improve the Surface Integrity(SI)of the nickel-based alloy Inconel 718 used in critical aero-engine components.Complementarily,the relaxation of RS is analyzed by in-situ annealing tests at in-service temperature combined with X-ray diffraction measurement.For this purpose,age hardened Inconel 718 discs were turned as reference condition,and then a pneumatic MHP tool was used under different conditions:two tool diameters(4 mm and 12 mm),feed rates(2.5 m/min and 5.0 m/min)and stepover distances(0.07 mm and 0.35 mm).Subsequently,surface topography characterization,RS measurements,nanoindentation tests,and microstructural observations were conducted.The in-situ annealing tests were done in the X-ray diffractometer at 550°C for exposure periods from 0 to 20 h.The results demonstrate that 4 mm diameter tools generate smooth surfaces and induce significant compressive RS within a0.5 mm thick layer.Residual stresses are relaxed,but they remain compressive even after a long thermal exposure.The microstructure of the surface layer(<10–15μm)was affected by the preceding turning operation,but importantly,MHP did not induce additional damage.
基金supported by the National Natural Science Foundation of China“Study on the evolution law of discharge channel and deformation suppression method for low-pressure micro-arc milling machining of aerospace thin-walled parts”(52265061)The Tianshan Innovation Team“Robotics and intelligent equipment technology science and technology innovation team”(2022D14002).
文摘To address problems in surface integrity and machining allowance distribution during combined electric arc-mechanical milling,this paper takes TC4 as the research object,examines the influence of electric arc milling(EAM)depth on recast layer thickness and surface roughness,alongside an analysis of the recast layer’s organization characteristics and sur-face morphology.A comparative evaluation of cutting forces,surface roughness,and surface hardening is conducted between combined milling and conventional mechanical milling.Key findings reveal that electric arc machining produces a recast layer with a hardness of 313.21 HV.As the EAM depth increases,the localized recast layer thickness and peak-to-valley(PV)differ-ences also rise.To ensure effective surface defect removal,the machining allowance for subsequent mechanical milling must exceed the combined thickness of the recast layer and the PV difference.Under identical parameters,combined milling yields higher surface roughness(0.584μm)and greater surface hardening(10.4%)compared to mechanical milling alone,alongside an 18.716 N increase in cutting force.Response surface methodology(RSM)analysis identifies feed per tooth as the most significant factor affecting surface roughness,followed by spindle speed,with milling depth having the least influence.
基金supported by the National Natural Science Foundation of China(Nos.92160301,92060203,52175415,52205475,and 52322510)the Science Center for Gas Turbine Project(No.P2023-B-IV-003-001)+1 种基金the Huaqiao University Engineering Research Center of Brittle Materials Machining(No.2023IME-001)the Natural Science Foundation of Jiangsu Province(No.BK20210295).
文摘Machined surface integrity of workpieces in harsh environments has a remarkable influence on their performance.However,the complexity of the new type of machining hinders a comprehensive understanding of machined surface integrity and its formation mechanism,thereby limiting the study of component performance.With increasing demands for high-quality machined workpieces in aerospace industry applications,researchers from academia and industry are increasingly focusing on post-machining surface characterization.The profile grinding test was conducted on a novel single-crystal superalloy to simulate the formation of blade tenons,and the obtained tenons were characterized for surface integrity elements under various operating conditions.Results revealed that ultrasonic vibration-assisted grinding(UVAG)led to multiple superpositions of abrasive grain trajectories,causing reduced surface roughness(an average reduction of approximately29.6%)compared with conventional grinding.After examining the subsurface layer of UVAG using transmission electron microscopy,the results revealed that the single-crystal tenon grinding subsurface layer exhibited a gradient evolution from the near-surface to the substrate.This evolution was characterized by an equiaxed nanocrystalline layer measuring 0.34μm,followed by a submicrocrystalline grain-forming zone spanning 0.6μm and finally,a constituent phase-twisted dis-torted deformation zone over 0.62μm.Under normal grinding conditions,the tenon exhibited low surface hardening(not exceeding 15%),and residual compressive stresses were observed on its surface.In cases where grinding burns occurred,a white layer appeared on the tenon's surface,which demonstrated varying thicknesses along the teeth from top to root due to thermal-force-structural coupling effects.Additionally,these burns introduced residual tensile stresses on the tenon's surface,potentially substantially affecting its fatigue life.This paper enhances our understanding of UVAG processes and establishes a foundation for their application in manufacturing singlecrystal turbine blades for next-generation aero-turbine engines.
基金financially supported by the National Natural Science Foundation of China(Nos.92160301,92060203,52175415 and 52205475)the Science Center for Gas Turbine Project(Nos.P2022-AB-IV-002-001 and P2023-B-IV-003-001)+5 种基金the Natural Science Foundation of Jiangsu Province(No.BK20210295)the Superior Postdoctoral Project of Jiangsu Province(No.2022ZB215)the National Key Laboratory of Science and Technology on Helicopter Transmission(Nanjing University of Aeronautics and Astronautics)(No.HTL-A-22G12)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX23-0355)the China Postdoctoral Science Foundation(No.2023T160315)the Interdisciplinary Innovation Fund for Doctoral Students of Nanjing University of Aeronautics and Astronautics(KXKCXJJ202305).
文摘Gamma titanium-aluminum(γ-TiAl)intermetallic compounds are increasingly used in manufacturing key hot-end components(e.g.,blade tenon)in aero engines due to their high specific strength and lightweight properties.Creep feed profile grinding(CFPG)as a crucial precision process that is applied to produce the final profile of the blade tenon.However,sudden surface burns and microcracks of machined c-TiAl blade tenon often occur because of its low plasticity and high strength during grinding processes,leading to poor surface integrity.In this work,CFPG experiments based on the profile characteristics ofγ-TiAl blade tenon were performed and an associated undeformed chip thickness model considering grain–workpiece contact condition was established to explore the evolution of the surface integrity.Subsequently,the surface integrity was analyzed at different positions of the blade tenon in terms of surface roughness and morphology,metallographic structure,microhardness,and residual stress.Results show that the profile characteristics of blade tenon have a significant influence on machined surface integrity because of the thermomechanical effect at various detecting positions.The residual stress was established based on the undeformed chip thickness model considering the profile structure,with a prediction error of 10%–15%.The thermomechanical effect is more obvious at the bottom area,where the surface roughness,work hardening degree,and subsurface plastic deformation range are the largest,while the values at the bevel area are the smallest.Based on the undeformed chip thickness model,a residual stress finite element simulation was conducted by employing thermomechanical coupled effects.In addition,the error between the simulation and the experiment was between 10%–15%.Strain and strain rate equations were established through the relationship between material displacement and depth.The average strain and strain rate of the ground surface when ap is 1.0 mm are 18.8%and 33.2%larger than when ap is 0.5 mm,respectively.This study deepens the understanding of surface integrity under the influence of CFPGγ-TiAl and provides a practical reference and theoretical basis for realizing high-quality profile grinding of other complex parts.
基金supported by the National Natural Science Foundation of China(Grant Nos.51631007 and 51971171).
文摘Current Ti-based orthopedic implants often suffer from fatigue damage,therefore shortening their service lifespan.To solve this issue,in this study,mechanically polished Ti-6Al-7Nb(P-Ti6Al7Nb)was subjected to surface mechanical attrition treatment(SMAT).Effects of various SMAT process parameters,including ball diameter and treatment duration,on the surface integrity of P-Ti6Al7Nb were investigated,specifically in terms of surface quality,surface nanocrystalline layer,and residual stress.Subsequently,the microstructure,in-depth residual stress and microhardness distributions,surface roughness,and fatigue behavior in simulated body fluids of optimally SMATed Ti-6Al-7Nb(S-Ti6Al7Nb)were examined and compared to those of P-Ti6Al7Nb.Results showed that based on the experimental conditions established in the present research,the optimal parameters were determined to be a 3 mm ball diameter and a 15 min treatment duration,which resulted in excellent surface integrity;S-Ti6Al7Nb showed a 300μm-thick gradient nanostructured layer comprising the thickest nanocrystalline layer of about 20μm,a 1000μm-deep residual compressive stress field with the maximum surface residual compressive stress,and a microconcave topography but free of any defects or cracks.The microstructural evolution mechanism was also elucidated,revealing that the combination of multidirectional primary and secondary twins’intersections and twin-dislocation interactions contributed to grain refinement.Compared to P-Ti6Al7Nb,S-Ti6Al7Nb exhibited a 40%improvement in fatigue strength,owing to synergistic effects of the gradient nanostructured layer,surface work hardening,high amplitude of residual compressive stress,and improved surface integrity.These factors effectively prevented the initiation of fatigue crack at the surface and shifted it to the sublayer,and inhibited the subsequent crack propagation.
基金supported financially by the National Natural Science Foundation of China(Nos.52275148 and U21B2077)Natural Science Foundation of Shanghai(20ZR1415300)+1 种基金Innovation Program of Shanghai Municipal Education Commission(2019-01-07-00-02-E00068)Innovation Program Phase II of AECC Commercial Aircraft Engine Co.Ltd.(Grant No.HT-3RJC1053-2020)。
文摘Submerged abrasive waterjet peening(SAWJP)is an effective anti-fatigue manufacturing technology that is widely used to strengthen aeroengine components.This study investigated the correlation of SAWJP process parameters on surface integrity and fatigue life of titanium alloy TA19.SAWJP with different water pressures and standoff distances(SoDs)was conducted on the TA19 specimens.The surface integrity of the specimens before and after SAWJP with different process parameters was experimentally studied,including microstructure,surface roughness,microhardness,and compressive residual stress(CRS).Finally,fatigue tests of the specimens before and after SAWJP treatment with different process parameters were carried out at room temperature.The results highlighted that the fatigue life of the TA19 specimen can be increased by 5.46,5.98,and 6.28 times under relatively optimal process parameters,which is mainly due to the improved surface integrity of the specimen after SAWJP treatment.However,the fatigue life of specimens treated with improper process parameters is decreased by 0.55 to 0.69 times owing to the terrible surface roughness caused by the material erosion.This work verifies that SAWJP can effectively improve the surface integrity and fatigue life of workpieces,and reveals the relationship between process parameters,surface integrity,and fatigue life,which provides support for the promotion of SAWJP in the manufacturing fields.
基金Supported by National Natural Science Foundation of China(Nos.52375399,91960203 and 51975035)Chinese Aeronautical Establishment Aeronautical Science Foundation(No.2022Z045051001).
文摘Advanced hole-making process is of great importance to enhance the fatigue performance of Al-Li alloy part in aviation industry.Ultrasonic peening drilling(UPD),in which an ultrasonic transversal vibration is applied to the cutting tools,is a recently proposed hole-making method that integrates precision-machining and surface strengthening by single-shot operation.In the study,kinematics,material removal mechanism and strengthening mechanism for UPD of Al-Li alloy by helical fluted reamers are analyzed.The effect of transversal vibration on the cutting performance and surface integrity is studied through comparative experiments between UPD and conventional drilling(CD)of Al-Li alloy holes.The experimental results show that UPD exhibits superior cutting performance with a maximum reduction of 52.6%in thrust force and 52.3%in torque,respectively,compared to CD.Moreover,narrower dimensional tolerance is obtained in UPD due to the reduced transversal force and improved machining stability.Additionally,deeper plastic deformation,higher surface microhardness and residual compressive stress of machined holes are obtained by UPD.The electron back-scattered diffraction(EBSD)analysis confirms that deeper machined affect area and grain refinement are realized in UPD.Therefore,the results indicate that UPD is a feasible method for achieving high-precision and strengthened holes for Al-Li alloy.
基金support from the National Science Fund of China(52325506)the National Science and Technology Major Project(2017-VII-0002-0095)Fundamental Research Funds for the Central Universities(DUT22LAB501)。
文摘Fatigue properties are crucial for critical aero-engine components in extreme serviceenvironments,which are significantly affected by surface integrity(SI)indexes(especially surface topography,residual stressσ_(res),and microhardness)after machining processes.Normal-direction ultrasonic vibration-assisted face grinding(ND-UVAFG)has advantages in improving the machinability of Inconel 718,but there is a competitive relationship between higher compressiveσ_(res)and higher surface roughness R_(a)in affecting fatigue strength.The lack of a quantitative relationship between multiple SI indexes and fatigue strength makes theindeterminacy of a regulatory strategy for improving fatigue properties.In this work,a model of fatigue strength(σ_f)_(sur)considering multiple SI indexes was developed.Then,high-cycle fatigue tests were carried out on Inconel 718 samples with different SI characteristics,and the influence of ND-UVAFG process parameters on SI was analyzed.Based on SI indexes data,the(σ_f)_(sur)distribution in the grinding surface layer for ND-UVAFG Inconel 718 samples was determined using the developed model,and then the fatigue crack initiation(FCI)sites were furtherpredicted.The predicted FCI sites corresponded well with the experimental results,therebyverifying this model.A strategy for improving the fatigue life was proposed in this work,which was to transfer the fatigue source from the machined surface to the bulk material by controlling the SI indexes.Finally,a critical condition of SI indexes that FCI sites appeared on the surface or in bulk material was given by fitting the predicted results.According to the critical condition,an SI field where FCI sites appeared in the bulk material could be obtained.In this field,thefatigue life of Inconel 718 samples could be improved by approximately 140%.
基金National Basic Research Program of China (2009CB724403)Program for Changjiang Scholars and Innovative Research Team in University (IRT0837)Program for New Century Excellent Talents in University from Ministry of Education of China (NCET-07-0435)
文摘The technique of creep feed grinding is most suitable for geometrical shaping, and therefore has been expected to improve effectively material removal rate and surface quality of components with complex profile. This article studies experimentally the effects of process parameters （i.e. wheel speed, workpiece speed and depth of cut） on the grindability and surface integrity of cast nickel-based superalloys, i.e. K424, during creep feed grinding with brazed cubic boron nitride （CBN） abrasive wheels. Some important factors, such as grinding force and temperature, specific grinding energy, size stability, surface topography, microhardhess and microstructure alteration of the sub-surface, residual stresses, are investigated in detail. The results show that during creep feed grinding with brazed CBN wheels, low grinding temperature at about 100 ℃ is obtained though the specific grinding energy of nickel-based superalloys is high up to 200-300 J/mm^3. A combination of wheel speed 22.5 m/s, workpiece speed 0.1 m/min, depth of cut 0.2 mm accomplishes the straight grooves with the expected dimensional accuracy. Moreover, the compressive residual stresses are formed in the bum-free and crack-free ground surface.
基金National Fundamental Research Program of China (2009CB724403)Program for New Century Excellent Talents in University from Ministry of Education of China (NCET-07-0435)
文摘Titanium alloy tenon is creep feed ground with monolayer brazed cubic boron nitride （CBN） shaped wheels. The dimension accuracy of the tenon is assessed and the results indicate that it completely meets the requirement of blade tenon of aero-engine. Residual stresses, surface roughness, microstructure and microhardness are measured on ground surfaces of the specimen, which are all compared with that ground with vitrified CBN wheels. Under all the circumstances, compressive residual stress is obtained and the depth of the machining affected zone is found to be less than 40 μm. No phase transformation is observed at depths of up to 100 lain below the surface, though plastic deformation is visible in the process of grain refinement. The residual stress and microhardness of specimens ground with brazed CBN wheels are observed to be lower than those ground with vitrified ones. The arithmetic mean roughness （Ra） values obtained are all below 0.8μm.
基金Supported by the National Natural Science Foundation of China(50975141)the National Scienceand Technology Major Project(2010ZX04012-042)the Aeronautical Science Foundation(2010352005)~~
文摘Surface integrity of a new damage-tolerant titanium alloy （TC21）, including surface roughness, microhardness and metallurgical structure is investigated when normal and high speed milling are used at different tool wear status. Results show that good surface integrity of TC21 can be obtained in high speed milling. In addition, even in acutely worn stages, there is no so-called serious hardening layer （or white layer） according to the studies on microhardness and metallurgical structure.
文摘To evaluate the new designed cutting tools for high-efficiency milling of the hardened die steel SKD11,surface integrities of millers with different geometric structures are analyzed, considering the surface roughness, micrograph of chips, surface microhardness, residual stress and metallurgical texture of the surface layer. The in fluences of geometric characteristics of different cutting tools and their wear characteristics on the surface integrity are studied. Results show that the milling tool with rake angle; 5 of the hardened diesteel. The generation of saw-tooth chips is depressed when a reasonable positive rake angle is selected. And the compressive residual stress is induced on the machined surface in milling the hardened die steel. The occurrence of surface softening is postponed by increasing the clearance angle and reducing the tool flank wear.
基金supported by the National Natural Science Foundation of China(Grant Nos.52375420,52322510)Natural Science Foundation of Heilongjiang Province of China(Grant No.YQ2023E014)+6 种基金National Key Research and Development Program of China(Grant No.2021YFB3400403)Shenzhen Science and Technology Program(Grant No.GNCWSSJH20240032)Self-Planned Task(Grant No.SKLRS202214B)of State Key Laboratory of Robotics and System(HIT),China Postdoctoral Science Foundation(Grant No.2022T150163)Young Elite Scientists Sponsorship Program by CAST(Grant No.YESS20220463)Open Fund of Key Laboratory of Microsystems and Microstructures Manufacturing(HIT)(Grant No.2022KM004)Open Foundation of Hunan Provincial Key Laboratory of High Efficiency and Precision Machining of Difficult-to-Cut Material(Grant No.E22445)Fundamental Research Funds for the Central Universities(Grant Nos.HIT.OCEF.2022024,FRFCU5710051122)。
文摘Silicon carbide(SiC)ceramics are extensively utilized in aerospace,national defense,and petrochemical industries due to their superior physical and chemical properties.The processing of bulk SiC ceramics necessitates precise and efficient grinding techniques to produce components with satisfactory functionality.However,the inherent high hardness and brittleness of SiC ceramics present significant challenges during grinding,leading to severe brittle fracture and tool wear that compromise both surface integrity and production efficiency.Although ductile-regime grinding of SiC ceramics can be achieved by enhancing machine tool accuracy and stiffness while optimizing wheel performance alongside appropriate selection of process parameters,a comprehensive summary of the mechanisms underlying damage evolution during grinding is lacking,and a mature grinding process for SiC ceramics has yet to be developed.To bridge this gap,the sintering technologies,mechanical properties,and microstructures of SiC ceramics were briefly covered.The grinding-induced damage mechanism and low-damage grinding technologies of SiC ceramics were summarized.The fundamental science underlying the ductile deformation and removal mechanisms of brittle solids was emphasized.Additionally,attention was directed towards the critical role of hybrid energy field grinding in minimizing brittle damages and promoting removal efficiency.This review not only elucidates the intrinsic interactions between the work material and abrasives,but also offers valuable insights for optimizing the grinding processes of brittle solids.
基金financially supported by the National Key Research and Development Project,China(Nos.2018YFA0703300,2022YFB4600019)the National Natural Science Foundation of China(Nos.52275148,52405154)+2 种基金the Innovation Program Phase II of AECC Commercial Aircraft Engine Co.Ltd,China(No.HT-3RJC1053-2020)support by the Postdoctoral Fellowship Program of CPSF,China(No.GZB20240219)the Shanghai Sailing Program,China(No.24YF2708100).
文摘Submerged Abrasive Waterjet Peening(SAWJP)shows great application potential in augmenting the fatigue properties of metallic parts.Thus,the present work aims to investigate the influence of SAWJP on the Surface Integrity(SI)and Fretting Fatigue(FF)properties of Inconel 718(IN718)superalloy and illustrate the microstructural evolution,FF life improvement,and fretting wear mechanism.First,the SI of the IN718 specimen was examined following treatment via SAWJP.Results showed that the specimen subjected to SAWJP formed a total plastic deformation layer of 56μm.The maximum microhardness and Compressive Residual Stress(CRS)measured across the depth of the SAWJP-treated specimens exhibited an increase in values ranging between 522 HV and 541 HV and 1171–1380 MPa,respectively.The FF test results of the specimen before and after SAWJP treatment at ambient temperatures indicated that the FF life of the SAWJP-treated specimen surpassed that of the as-received specimen by a factor of 2.81.The examination of the FF fracture,contact surface,and crack propagation behavior revealed the crucial factors contributing to the enhanced FF resistance of the IN718 specimen,including the gradient nanostructure characterized by ultra-refined grains,substantial CRS,and elevated microhardness,which were all induced by the SAWJP treatment.
基金supported by the National Natural Science Foundation of China(Nos.91960203 and 52375399)the Chinese Aeronautical Establishment Aeronautical Science Foundation(No.2022Z045051001).
文摘Ultrasonic elliptical vibration cutting(UEVC)with clockwise elliptical vibration has made notable achievements in precision machining;however,its critical cutting speed limits its application to low-speed machining tasks.Meanwhile,rotary ultrasonic elliptical machining(RUEM)with clockwise elliptical vibration has been validated as an effective high-speed cutting technology.Unfortunately,conventional RUEM leads to increased surface roughness.To address this issue and enhance machining quality,we propose a novel RUEM method employing an anticlockwise vibration direction,called anticlockwise rotary ultrasonic elliptical machining(ARUEM).The mechanisms of surface formation and subsurface strengthening for ARUEM are analyzed.Experimental validations were performed on Ti-6Al-4V alloy,revealing that ARUEM achieved substantially lower ridge heights and up to a 50%reduction in surface roughness compared to conventional RUEM.Additionally,relative to conventional milling,ARUEM resulted in up to 122.6%thicker plastic deformation layers,53.4%higher surface residual compressive stress,and 19.3%greater surface micro-hardness.This study showcases a promising method for high-performance milling of Ti-6Al-4V,offers new insights into RUEM by examining the influence of vibration direction,and enhances understanding of surface formation and subsurface strengthening in the ARUEM method.
基金National High-tech Research and Development Program of China (2009AA04Z116)Program for Changjiang Scholars and Innovative Research Team in University ( IRT0837)
文摘Titanium alloys are widely used in aeronautics that demand a good combination of high strength, good corrosion resistance and low mass. The mechanical properties lead to challenges in machining operations such as high process temperature as well as rapidly increasing tool wear. The conventional tool materials are not able to maintain their hardness and other mechanical prop- erties at higher cutting temperatures encountered in high speed machining. In this work, the new material tools, which are poly- crystalline diamond （PCD） and polycrystalline cubic boron nitride （PCBN） tools, are used in high-speed milling of Ti-6.5AI-2Zr-IMo-IV （TA15） alloy. The performance and wear mechanism of the tools are investigated. Compared to PCBN tool, PCD tool has a much longer tool life, especially at higher cutting speeds. Analyses based on the SEM and EDX suggest that attrition, adhesion and diffusion are the main wear mechanisms of PCD and PCBN tools in high-speed milling of TA 15. Oxida- tion wear is also observed at PCBN tool/workpiece interface. Roughness, defects, micro-hardness and microstructure of the ma- chined surface are investigated. The recorded surface roughness values with PCD/PCBN tools are bellow 0.3 μm at initial and steady cutting stage. Micro-hardness analysis shows that the machined surface hardening depth with PCD and PCBN tools is small. There is no evidence of sub-surface defects with PCD and PCBN tools. It is concluded that for TA15 alloy, high-speed milling can be carried out with PCD/PCBN tools.
基金supported by the Aeronautical Science Foundation of China (No.2016ZE51039)
文摘Surface topography of superalloy GH4169 workpieces machined by milling and grinding is different significantly. Meanwhile, surface roughness, as one of the main indicators of machined surface integrity, has a great influence on the fatigue behavior of workpieces. Based on analyzing the formation mechanism and characteristics of surface roughness utilizing different machining processes and parameters, the machined surface roughness curve can be decoupled into two parts utilizing frequency spectrum analysis, which are kinematic surface roughness curve and stochastic surface roughness curve. The kinematic surface roughness curve is influenced by machining process,parameters, geometry of the cutting tool or wheel, the maximum height of which is expressed as Rz＇.By subtracting the kinematic part from the measurement curve, the stochastic surface roughness curve and its maximum height Rz＂ can be obtained, which is influenced by the defects of cutting tool edge or abrasive grains, built-up edges（BUE）, cracks, high frequency vibration and so on. On the other hand, the results of decoupling analysis of surface roughness curves indicate that Raand Rz values of milling GH4169 are 2–5 times and 1–3 times as high as those of grinding, while Rz＂ value of milling is 13.85%–37.7% as high as that of grinding. According to the results of fatigue life tests of specimens machined by milling and grinding, it can be concluded that fatigue behavior of GH4169 decreases with the increase of Rz＂monotonically, even utilizing different machining processes.
基金Supported by Science Fund for Creative Research Groups of NSFC(51621064)National Natural Science Foundation of China(Grant No.51475074,11302043)the Fundamental Research Funds for the Central Universities(DUT15QY37)
文摘The integral impeller and blisk of an aero-engine are high performance parts with complex structure and made of difficult-to-cut materials. The blade surfaces of the integral impeller and blisk are functional surfaces for power transmission, and their surface integrity has signif- icant effects on the aerodynamic efficiency and service life of an aero-engine. Thus, it is indispensable to finish and strengthen the blades before use. This paper presents a comprehensive literature review of studies on finishing and strengthening technologies for the impeller and blisk of aero-engines. The review includes independent and inte- grated finishing and strengthening technologies and dis- cusses advanced rotational abrasive flow machining with back-pressure used for finishing the integral impeller and blisk. A brief assessment of future research problems and directions is also presented.
