A numerical method has been developed to extract the composition-dependent interdiffusivity from the concentration profiles in the aluminide coating prepared by pack cementation. The procedure is based on the classic ...A numerical method has been developed to extract the composition-dependent interdiffusivity from the concentration profiles in the aluminide coating prepared by pack cementation. The procedure is based on the classic finite difference method (FDM). In order to simplify the model, effect of some alloying elements on interdiffusivity can be negligible. Calculated results indicate the interdiffusivity in aluminide coating strongly depends on the composition and give the formulas used to calculate interdiffusivity at 850, 950 and 1050癈. The effect on interdiffusivity is briefly discussed.展开更多
One-dimensional artificial scattering planes can form in the direction perpendicular to the surface of the films when the compositional modulation period is shorter. Similar to real crystal lattice planes, these artif...One-dimensional artificial scattering planes can form in the direction perpendicular to the surface of the films when the compositional modulation period is shorter. Similar to real crystal lattice planes, these artificial scattering planes produce Bragg diffraction with X-ray radiation. Since the modulation period is longer than the general lattice period, the Bragg diffraction peak appears at the position of lower angle (2θ is generally lower than 10°). The diffraction peaks produced by compositional modulation are called modulation peaks.展开更多
The interdiffusion coefficients in Al_(0.2)CoCrFeNi,CoCrCu_(0.2)FeNi,and CoCrFeMn_(0.2)Ni high-entropy alloys were efficiently determined by combining diffusion couple experiments and high-throughput determination of ...The interdiffusion coefficients in Al_(0.2)CoCrFeNi,CoCrCu_(0.2)FeNi,and CoCrFeMn_(0.2)Ni high-entropy alloys were efficiently determined by combining diffusion couple experiments and high-throughput determination of interdiffusion coefficients(HitDIC)software at 1273−1373 K.The results show that the addition of Al,Cu,and Mn to CoCrFeNi high-entropy alloys promotes the diffusion of Co,Cr,and Fe atoms.The comparison of tracer diffusion coefficients indicates that there is no sluggish diffusion in tracer diffusion on the thermodynamic temperature scale for the present Al_(0.2)CoCrFeNi,CoCrCu_(0.2)FeNi,and CoCrFeMn_(0.2)Ni high-entropy alloys.The linear relationship between diffusion entropy and activation energy reveals that the diffusion process of atoms is unaffected by an increase in the number of components as long as the crystal structure remains unchanged.展开更多
Oxidation behavior of NiCrAlY nanocrystalline coatings with different Cr contents at 1050 and 1150℃is investigated.The results indicate that Al2O3 scales can be formed on NiCrAlY nanocrystalline coatings after oxidat...Oxidation behavior of NiCrAlY nanocrystalline coatings with different Cr contents at 1050 and 1150℃is investigated.The results indicate that Al2O3 scales can be formed on NiCrAlY nanocrystalline coatings after oxidation at high temperature.And their formation and thickening cannot be affected by the change of Cr contents in NiCrAlY coatings.During service,Cr in the coating can affect the microstructure of Ni-based single crystal superalloy.At 1050℃,Cr in the coating can diffuse into the superalloy,destroy its microstructure,and lead to the formation of interdiffusion zone and the precipitation of needle-like topologically closed-packed phase.The higher the Cr content in NiCrAlY the coating is,the more obvious the phenomenon is.However,after oxidation at 1150℃for 100 h,no obvious changes were observed in the microstructure of CMSX-4 single crystal superalloy beneath the three kinds of NiCrAlY nanocrystalline coatings.展开更多
The as-deposited coating-substrate microstructure has been identified to substantially influence the high-cycle fatigue(HCF)behavior of Ni-based single-crystal(SX)superalloys at 900℃,but the impact of degraded micros...The as-deposited coating-substrate microstructure has been identified to substantially influence the high-cycle fatigue(HCF)behavior of Ni-based single-crystal(SX)superalloys at 900℃,but the impact of degraded microstructure on the HCF behavior remains unclear.In this work,a PtAl-coated third-generation SX superalloy with sheet specimen was thermal-exposed at 1100℃ with different durations and then subjected to HCF tests at 900℃.The influence of microstructural degradation on the HCF life and crack initiation were clarified by analyzing the development of microcracks and coating-substrate microstructure.Notably,the HCF life of the thermal-exposed coated alloy increased abnormally,which was attributed to the transformation of the fatigue crack initiation site from surface mi-crocracks to internal micropores compared to the as-deposited coated alloy.Although the nucleation and growth of surface microcracks occurred along the grain boundaries in the coating and the interdiffusion zone(IDZ)for both the as-deposited and the thermal-exposed coated alloys,remarkable differences of the microcrack growth into the substrate adjacent to the IDZ were observed,changing the crack initiation site.Specifically,the surface microcracks grew into the substrate through the cracking of the non-protective oxide layers in the as-deposited coated alloy.In comparison,the hinderance of the surface microcracks growth was found in the thermal-exposed coated al-loy,due to the formation of a protective Al_(2)O_(3) layer within the microcrack and theγ′rafting in the substrate close to the IDZ.This study will aid in improving the HCF life prediction model for the coated SX superalloys.展开更多
A novel NiAlTa blade tip protective coating is designed and its oxidation,hot corrosion,and interdiffusion with DD5 single-crystal superalloys are investigated.NiAlTa coatings exhibit low oxidation rates.The dragging ...A novel NiAlTa blade tip protective coating is designed and its oxidation,hot corrosion,and interdiffusion with DD5 single-crystal superalloys are investigated.NiAlTa coatings exhibit low oxidation rates.The dragging effect of Ta on Al hinders the external diffusion of Al.Ta that accumulates at the Al_(2)O_(3)grain boundaries reduces the internal diffusion of O by combining or reacting with it.NaCl aggravates the hot corrosion through self ustaining cycles of chlorination/oxidation.β-NiAl phase fails first as a diffusion channel for the corrosive medium.Significant element interdiffusion occurs.An interdiffusion zone and a secondary reaction zone are formed.Interdiffusion changes the percentage of elements,causing a phase transition of the coating.The volume change caused by the phase transition induces bulging and cracking of the oxide film.Furthermore,the oxidation,hot corrosion,and interdiffusion mechanisms are discussed.展开更多
The microstructural evolution of an aluminide coating,prepared by chemical vapor deposition on the inner surface of a superalloy blade,was comprehensively investigated during service in a real gas turbine.The as-depos...The microstructural evolution of an aluminide coating,prepared by chemical vapor deposition on the inner surface of a superalloy blade,was comprehensively investigated during service in a real gas turbine.The as-deposited coating exhibited a dual-layer structure:the outer layer predominantly composed of β and γ'phases,and the inner layer consisting mainly of β,γ',andσphases.A secondary reaction zone(SRZ),enriched with needle-like σ phases,developed inside the superalloy substrate beneath the coating.Despite the blade not being enriched with refractory elements,three types of topologically close-packed(TCP)phases—σ,μ,and P—precipitated.During the aluminizing process,the needle-like σ phase formed first,followed by the transformation of σ to P and μ phases,with P and μ nucleating within the σ phase.The transformation coordinate was proposed and simulated through density functional theory(DFT)calculations.Coherent relations were observed between different TCP phases and between TCP phases and superalloy substrate.The aluminide coating exhibited varying oxidation behaviors due to its microstructural diversity.Interfacial oxidation dominated the oxidation process,attributed to the enrichment of Ti in the inner coating layer and the co-oxidation of Ti and Al.The γ→γ'transformation within the SRZ led to the shrinkage of the original γ phase into line-like structures.Additionally,the aluminizing and homogenization processes were simulated using the DICTRA code,with results that align well with experimental observations.展开更多
Pure metal Fe films with thickness of about 100nm were deposited on Si （100） substrates by DC magnetron sputtering. Annealing was subsequently performed in a vacuum furnace in the temperature range of 600-1000℃ for...Pure metal Fe films with thickness of about 100nm were deposited on Si （100） substrates by DC magnetron sputtering. Annealing was subsequently performed in a vacuum furnace in the temperature range of 600-1000℃ for 2h. The samples were characterized by means of Rutherford backscattering （RBS） with 3MeV carbon ions. The RBS data were fitted with SIMNRA 6.0, and the results show the atomic interdiffusion in Fe/Si systems. The microstructures and crystal structures were characterized by scanning electron microscope and X-ray diffrac- tion. The effects of annealing on atomic interdiffusion, silicide formation, and microstructures in Fe/Si systems were analyzed.展开更多
The effect of high magnetic field on the atomic interdiffusion in Ni-Cu system was studied using the Cu/Ni/Cu diffusion couples. During the atomic interdiffusion in Ni-Cu system, it was found that the interdiffusion c...The effect of high magnetic field on the atomic interdiffusion in Ni-Cu system was studied using the Cu/Ni/Cu diffusion couples. During the atomic interdiffusion in Ni-Cu system, it was found that the interdiffusion coefficients increased with the increase of molar fraction of Ni atoms in the interdiffusion zones when the couples were annealed with or without the magnetic field. It was noted that all corresponding interdiffusion coefficients under the magnetic field are smaller than those without the magnetic field. The results demonstrate that the magnetic field retards the atomic interdiffusion in Ni-Cu system. This retardation is achieved through reducing the frequency factors but not changing the interdiffusion activation energies.展开更多
Powder mixture of pure Al and oxidized Si C was consolidated into 10%（mass fraction） Si Cp/Al composites at 250 °C by equal channel angular pressing and torsion（ECAP-T）. The valence states of Si for Si C part...Powder mixture of pure Al and oxidized Si C was consolidated into 10%（mass fraction） Si Cp/Al composites at 250 °C by equal channel angular pressing and torsion（ECAP-T）. The valence states of Si for Si C particulates and Al for the as-consolidated composites were detected by X-ray photoelectron spectroscopy（XPS）. The interfacial bondings of the composites were characterized by scanning electron microscopy（SEM）. The elements at the interface were linearly scanned by energy dispersive spectroscopy（EDS） and the EDS mappings of Si and Al were also obtained. The values of the nanohardness at different positions within 2 μm from the boundary of Si C particulate were measured. The results show that after ECAP-T, interfacial reaction which inhibits injurious interfacial phase occurs between Al and the oxide layer of Si C, and the element interdiffusion which can enhance interfacial bonding exists between Al and Si C. As ECAP-T passes increase, the reaction degree is intensified and the element interdiffusion layer is thickened, leading to the more smooth transition of the hardness from Si C to Al.展开更多
The influence of thermal treatment on Si 1-x Ge x/Si multiple-quantum wells (MQW) p-i-n photodiodes has been investigated by photocurrent spectroscopy combined with X-ray double crystal dif...The influence of thermal treatment on Si 1-x Ge x/Si multiple-quantum wells (MQW) p-i-n photodiodes has been investigated by photocurrent spectroscopy combined with X-ray double crystal diffraction.The cutoff wavelength is significantly reduced due to the Si-Ge interdiffusion and partial relaxation of the strained SiGe alloy.The values of the blue shift increase slowly with the annealing temperatures in the range of 750℃ to 850℃.However,the nonlinear changes in photocurrent intensities of the samples annealed at different temperatures have been observed,which is mainly dominated by the generation of misfit dislocations and the reduction of the point defects in the heating process.展开更多
In the 1940s, KIRKENDALL showed that diffusion in binary solid solutions cannot be described by only one diffusion coefficient. Rather, one has to consider the diffusivity of both species. His findings changed the tre...In the 1940s, KIRKENDALL showed that diffusion in binary solid solutions cannot be described by only one diffusion coefficient. Rather, one has to consider the diffusivity of both species. His findings changed the treatment of diffusion data and the theory of diffusion itself. A diffusion-based framework was successfully employed to explain the behaviour of the Kirkendall plane. Nonetheless, the complexity of a multiphase diffusion zone and the morphological evolution during interdiffusion requires a physico-chemical approach. The interactions in binary and more complex systems are key issues from both the fundamental and technological points of view. This paper reviews the Kirkendall effect from the circumstances of its discovery to recent developments in its understanding, with broad applicability in materials science and engineering.展开更多
MCrAlY(M=Ni and/or Co)overlay coating is widely used as a protective coating against high temperature oxidation and corrosion.However,due to its big difference in chemical composition with the underlying superalloy,el...MCrAlY(M=Ni and/or Co)overlay coating is widely used as a protective coating against high temperature oxidation and corrosion.However,due to its big difference in chemical composition with the underlying superalloy,elements interdiffusion occurs inevitably.One of the direct results is the formation of interdiffusion zone(IDZ)and secondary reaction zone(SRZ)with a high density of fine topological closed-packed phases(TCPs),weakening dramatically the mechanical properties of the alloy substrate.It is by now the main problem of modern high-temperature metallic coatings,but there are still hardly any reports studying the formation,growth and transformation of IDZ and SRZ in deep,as well as the precipitation of TCPs.In this work,a typical NiCrAlY coating is deposited by arc ion plating on a single-crystal superalloy N5.Elements interdiffusion between them and its relationship on microstructure were clarified.Cr rather than Al from the coating diffuses into the alloy at high temperatures and segregates immediately beneath their interface,contributing largely to the formation of IDZ.Simultaneously,diffusion of Ni from the deep alloy to IDZ leads to the formation and continuous expansion of SRZ.展开更多
A low-diffusion Ni Re Pt Al coating((Ni,Pt)Al outer layer in addition to a Re-rich diffusion barrier layer)was prepared on a Ni_(3)Al-base single crystal(SC)superalloy via electroplating and gaseous aluminizing treatm...A low-diffusion Ni Re Pt Al coating((Ni,Pt)Al outer layer in addition to a Re-rich diffusion barrier layer)was prepared on a Ni_(3)Al-base single crystal(SC)superalloy via electroplating and gaseous aluminizing treatments,wherein the electroplating procedures consisted of the composite deposition of Ni-Re followed by electroplating of Pt.In order to perform a comparison with conventional Ni Al and(Ni,Pt)Al coatings,the cyclic oxidation performance of the Ni Re Pt Al coating was evaluated at 1100 and 1150℃.We observed that the oxidation resistance of the Ni Re Pt Al coating was significantly improved by the greater presence of the residualβ-Ni Al phase in the outer layer and the lesser outward-diffusion of Mo from the substrate.In addition,the coating with the Re-rich diffusion barrier demonstrated a lower extent of interdiffusion into the substrate,where the thickness of the second reaction zone(SRZ)in the substrate alloy decreased by 25%.The mechanisms responsible for improving the oxidation resistance and decreasing the extent of SRZ formation are discussed,in which a particular attention is paid to the inhibition of the outward diffusion of Mo by the Re-based diffusion barrier.展开更多
The mechanical and diffusion properties of Ti-Ta-Fe alloys in the Ti-rich region were investigated by utilizing a high-throughput method, with the combination of nanoindentation and diffusion couple techniques.Five gr...The mechanical and diffusion properties of Ti-Ta-Fe alloys in the Ti-rich region were investigated by utilizing a high-throughput method, with the combination of nanoindentation and diffusion couple techniques.Five groups of ternary Ti-Ta-Fe diffusion couples were prepared after annealing at 1273 K for 25 h. The composition-dependent mechanical properties of bcc Ti-Ta-Fe system were experimentally determined by means of nanoindentation and electron probe microanalysis(EPMA) techniques. Moreover, the interdiffusion coefficients of Ti-Ta-Fe alloys at 1273 K were confirmed from the composition gradients of the ternary diffusion couples with the support of a pragmatic numerical inverse method. A composition-dependent database on the mechanical and diffusion properties of Ti-Ta-Fe alloys was carefully established and utilized for the discussion of the processability during the hot working. The results indicated that the content of Fe should be controlled for the Ti alloys with high hardness and low Young’s modulus.展开更多
High-temperature chromium(Cr)-zirconium(Zr)interdiffusion commonly occurs in Cr-coated zircaloys applied for enhanced accident-tolerant fuel(ATF)claddings.Such interdiffusion changes the interfacial microstructure and...High-temperature chromium(Cr)-zirconium(Zr)interdiffusion commonly occurs in Cr-coated zircaloys applied for enhanced accident-tolerant fuel(ATF)claddings.Such interdiffusion changes the interfacial microstructure and thus the fracture mechanism of the coating under external loading.In this study,the interdiffusion behavior in a magnetron sputtered Cr coating deposited on a Zr-4 alloy was studied in a vacuum environment at 1160C.In addition,the effect of interdiffusion on the microcracking behavior of the Cr coating was determined by in situ three-point bending tests.The experimental results show that the interdiffusion behavior resulted in the formation of a ZrCr2 layer,accompanied by the consumption of Cr coating and interfacial roughening.The growth of the diffusion layer followed a nearly parabolic law with respect to annealing time,and the residual stress of the annealed coating decreased with increasing annealing time.Under external loading,a large number of cracks were generated in the brittle interlayer,and some interfacial cracks were formed and grew at the ZrCr2/Zr-4 interface.Despite the remarkable microcracks in the ZrCr2 layer,the vacuum-annealed Cr coating has significantly fewer cracks than the original coating,mainly because of the recrystallization of the coating during annealing.展开更多
New experimental data are presented on the density and thermal expansion of solid and liquid magnesium and ultralight magnesium–lithium alloys containing 23.03 and 30.02 at.% Li, respectively. The measurements were p...New experimental data are presented on the density and thermal expansion of solid and liquid magnesium and ultralight magnesium–lithium alloys containing 23.03 and 30.02 at.% Li, respectively. The measurements were performed using the dilatometer method and the gamma-ray attenuation technique in the temperature range from 145 to 1244 K for magnesium and from 293 to ~1000 K for the alloys. The density changes during the solid?liquid phase transition were directly measured for Mg and the Mg70Li30 alloy. The temperature dependences and reference tables of the investigated volumetric properties were developed. A comparison of the obtained results with literature data was made. The study showed that the eutectic composition in the magnesium- lithium system differs from 23 at.% Li. The concentration dependence of molar volume of the magnesium-lithium liquid system was found to be almost linear in the interval of 0-30 at.% Li and deviated noticeably from the corresponding dependence for an ideal mixture.展开更多
NiCrAlY coatings are widely applied on various alloy components to enhance oxidation and/or corrosion resistance at high temperatures.However,elements interdiffusion occurs between them due to composition difference.A...NiCrAlY coatings are widely applied on various alloy components to enhance oxidation and/or corrosion resistance at high temperatures.However,elements interdiffusion occurs between them due to composition difference.Although various diffusion barriers(DBs)are reported,this problem is still far from completely solved as most ceramic barriers suffer from poor adherence,while the metallic barriers play a limited role.In this study,NiCrAlY coating was deposited onto a second-generation single-crystal superalloy by arc ion plating.A novel simple method is provided to address elements interdiffusion.By pre-oxidation at a moderate temperature,a thin scale of Ni(Co)O forms at the alloy surface.It transforms to be an alumina/NiCoCr alloy/alumina sandwich by an in-situ reaction with the overlaying NiCrAlY coating and the alloy substrate at high service temperatures,which offers good barrier ability in conjunction with strong adhesion.In the presence of such an alumina/alloy/alumina DB,the NiCrAlY coating provides high resistance to oxidation and scale spallation for the alloy substrate.展开更多
To refrain the interdiffusion of elements while holding good oxidation resistance,a(Ni,Pt)Al/Ni composite coating was prepared by sequential treatments of electroplating Ni and Pt and successive gaseous aluminization....To refrain the interdiffusion of elements while holding good oxidation resistance,a(Ni,Pt)Al/Ni composite coating was prepared by sequential treatments of electroplating Ni and Pt and successive gaseous aluminization.In comparison with normal(Ni,Pt)Al coating,high-temperature performance of the composite coating was evaluated in isothermal oxidation test at 1100℃.Both the two coatings exhibited good resistance against high-temperature oxidation,but the interdiffusion of elements between composite coating and single-crystal(SC)superalloy substrate was greatly relieved,in which the thickness of secondary reaction zone(SRZ)and the amount of precipitated topologically close-packed phase in the SC alloy matrix were significantly decreased.Mechanisms responsible for delaying rate of coating degradation and SRZ growth/propagation are discussed.展开更多
To reveal the influence of substrate/coating interdiffusion on the cyclic oxidation property of a metallic coating, cyclic oxida- tion behavior of an EB-PVD CoCrAIY coating on directionally solidified Ni-based superal...To reveal the influence of substrate/coating interdiffusion on the cyclic oxidation property of a metallic coating, cyclic oxida- tion behavior of an EB-PVD CoCrAIY coating on directionally solidified Ni-based superalloy DZ125 at 1 050℃ is investigated. The 40 μm thick CoCrA1Y coating has a cyclic oxidation life of around 160 h, and the oxidation constant is 1.915× 10^-7 mg4.cm^-8.s-1. However, severe spallation of the oxides containing Co, Cr, Ni, Ta and Ti occurs with longer cyclic oxidation. The degradation in oxidation resistance for the coating is related to the depletion of A1 due to the oxide spallation and interdiffu- sion. Severe interdiffusion between the coating and underlying substrate occurs at 1 050 ℃. The composition of the substrate has an important effect on the thermal cycling lifetime of the coating. The influencing mechanism is discussed.展开更多
文摘A numerical method has been developed to extract the composition-dependent interdiffusivity from the concentration profiles in the aluminide coating prepared by pack cementation. The procedure is based on the classic finite difference method (FDM). In order to simplify the model, effect of some alloying elements on interdiffusivity can be negligible. Calculated results indicate the interdiffusivity in aluminide coating strongly depends on the composition and give the formulas used to calculate interdiffusivity at 850, 950 and 1050癈. The effect on interdiffusivity is briefly discussed.
文摘One-dimensional artificial scattering planes can form in the direction perpendicular to the surface of the films when the compositional modulation period is shorter. Similar to real crystal lattice planes, these artificial scattering planes produce Bragg diffraction with X-ray radiation. Since the modulation period is longer than the general lattice period, the Bragg diffraction peak appears at the position of lower angle (2θ is generally lower than 10°). The diffraction peaks produced by compositional modulation are called modulation peaks.
基金supported by the National Natural Science Foundation of China(No.52374372)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.23KJB430042)+3 种基金the Jiangsu Province Large Scientific Instruments Open Sharing Autonomous Research Filing Project,China(No.TC2023A037)the Yangzhou City−Yangzhou University Cooperation Foundation,China(No.YZ2022183)High-end Talent Support Program of Yangzhou University,China,Qinglan Project of Yangzhou University,ChinaLvyangjinfeng Talent program of Yangzhou,China.
文摘The interdiffusion coefficients in Al_(0.2)CoCrFeNi,CoCrCu_(0.2)FeNi,and CoCrFeMn_(0.2)Ni high-entropy alloys were efficiently determined by combining diffusion couple experiments and high-throughput determination of interdiffusion coefficients(HitDIC)software at 1273−1373 K.The results show that the addition of Al,Cu,and Mn to CoCrFeNi high-entropy alloys promotes the diffusion of Co,Cr,and Fe atoms.The comparison of tracer diffusion coefficients indicates that there is no sluggish diffusion in tracer diffusion on the thermodynamic temperature scale for the present Al_(0.2)CoCrFeNi,CoCrCu_(0.2)FeNi,and CoCrFeMn_(0.2)Ni high-entropy alloys.The linear relationship between diffusion entropy and activation energy reveals that the diffusion process of atoms is unaffected by an increase in the number of components as long as the crystal structure remains unchanged.
基金supported by the National Natural Science Foundation of China(No.52001142)Young Elite Scientists Sponsorship Program by CAST(No.2022QNRC001)Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX22_3793).
文摘Oxidation behavior of NiCrAlY nanocrystalline coatings with different Cr contents at 1050 and 1150℃is investigated.The results indicate that Al2O3 scales can be formed on NiCrAlY nanocrystalline coatings after oxidation at high temperature.And their formation and thickening cannot be affected by the change of Cr contents in NiCrAlY coatings.During service,Cr in the coating can affect the microstructure of Ni-based single crystal superalloy.At 1050℃,Cr in the coating can diffuse into the superalloy,destroy its microstructure,and lead to the formation of interdiffusion zone and the precipitation of needle-like topologically closed-packed phase.The higher the Cr content in NiCrAlY the coating is,the more obvious the phenomenon is.However,after oxidation at 1150℃for 100 h,no obvious changes were observed in the microstructure of CMSX-4 single crystal superalloy beneath the three kinds of NiCrAlY nanocrystalline coatings.
基金financially supported by National Key Research and Development Program of China(No.2022YFB 3708100)the Science Center for Gas Turbine Project,China(No.P2021-A-IV-002-001)+1 种基金the National Natural Science Foundation of China(Nos.52331005 and 52201100)the State Key Laboratory for Advanced Metals and Materials,China(No.2024-Z02).
文摘The as-deposited coating-substrate microstructure has been identified to substantially influence the high-cycle fatigue(HCF)behavior of Ni-based single-crystal(SX)superalloys at 900℃,but the impact of degraded microstructure on the HCF behavior remains unclear.In this work,a PtAl-coated third-generation SX superalloy with sheet specimen was thermal-exposed at 1100℃ with different durations and then subjected to HCF tests at 900℃.The influence of microstructural degradation on the HCF life and crack initiation were clarified by analyzing the development of microcracks and coating-substrate microstructure.Notably,the HCF life of the thermal-exposed coated alloy increased abnormally,which was attributed to the transformation of the fatigue crack initiation site from surface mi-crocracks to internal micropores compared to the as-deposited coated alloy.Although the nucleation and growth of surface microcracks occurred along the grain boundaries in the coating and the interdiffusion zone(IDZ)for both the as-deposited and the thermal-exposed coated alloys,remarkable differences of the microcrack growth into the substrate adjacent to the IDZ were observed,changing the crack initiation site.Specifically,the surface microcracks grew into the substrate through the cracking of the non-protective oxide layers in the as-deposited coated alloy.In comparison,the hinderance of the surface microcracks growth was found in the thermal-exposed coated al-loy,due to the formation of a protective Al_(2)O_(3) layer within the microcrack and theγ′rafting in the substrate close to the IDZ.This study will aid in improving the HCF life prediction model for the coated SX superalloys.
基金financially supported by the Strategic Priority Research Program of the Chinese Academy of Sciences,Grant(No.XDB 047010204)Liaoning Key Laboratory of Aero-engine Material Tribology for both financial and facility support
文摘A novel NiAlTa blade tip protective coating is designed and its oxidation,hot corrosion,and interdiffusion with DD5 single-crystal superalloys are investigated.NiAlTa coatings exhibit low oxidation rates.The dragging effect of Ta on Al hinders the external diffusion of Al.Ta that accumulates at the Al_(2)O_(3)grain boundaries reduces the internal diffusion of O by combining or reacting with it.NaCl aggravates the hot corrosion through self ustaining cycles of chlorination/oxidation.β-NiAl phase fails first as a diffusion channel for the corrosive medium.Significant element interdiffusion occurs.An interdiffusion zone and a secondary reaction zone are formed.Interdiffusion changes the percentage of elements,causing a phase transition of the coating.The volume change caused by the phase transition induces bulging and cracking of the oxide film.Furthermore,the oxidation,hot corrosion,and interdiffusion mechanisms are discussed.
基金financially supported by the National Natural Science Foundation of China(Nos.U2341257,12402112,and 92371204)the Guangdong Basic and Applied Basic Research Foundation(No.2022A1515110198)+2 种基金the National Science and Technology Major Project of China(Nos.J2022-V-0003-0029 and J2019-Ⅲ-0008-0051)the Innovation Capability Support Program of Shaanxi(No.2022TD-28)the Fundamental Research Funds for the Central Universities(No.QTZX23014).
文摘The microstructural evolution of an aluminide coating,prepared by chemical vapor deposition on the inner surface of a superalloy blade,was comprehensively investigated during service in a real gas turbine.The as-deposited coating exhibited a dual-layer structure:the outer layer predominantly composed of β and γ'phases,and the inner layer consisting mainly of β,γ',andσphases.A secondary reaction zone(SRZ),enriched with needle-like σ phases,developed inside the superalloy substrate beneath the coating.Despite the blade not being enriched with refractory elements,three types of topologically close-packed(TCP)phases—σ,μ,and P—precipitated.During the aluminizing process,the needle-like σ phase formed first,followed by the transformation of σ to P and μ phases,with P and μ nucleating within the σ phase.The transformation coordinate was proposed and simulated through density functional theory(DFT)calculations.Coherent relations were observed between different TCP phases and between TCP phases and superalloy substrate.The aluminide coating exhibited varying oxidation behaviors due to its microstructural diversity.Interfacial oxidation dominated the oxidation process,attributed to the enrichment of Ti in the inner coating layer and the co-oxidation of Ti and Al.The γ→γ'transformation within the SRZ led to the shrinkage of the original γ phase into line-like structures.Additionally,the aluminizing and homogenization processes were simulated using the DICTRA code,with results that align well with experimental observations.
文摘Pure metal Fe films with thickness of about 100nm were deposited on Si （100） substrates by DC magnetron sputtering. Annealing was subsequently performed in a vacuum furnace in the temperature range of 600-1000℃ for 2h. The samples were characterized by means of Rutherford backscattering （RBS） with 3MeV carbon ions. The RBS data were fitted with SIMNRA 6.0, and the results show the atomic interdiffusion in Fe/Si systems. The microstructures and crystal structures were characterized by scanning electron microscope and X-ray diffrac- tion. The effects of annealing on atomic interdiffusion, silicide formation, and microstructures in Fe/Si systems were analyzed.
基金Project(2011CB012803) supported by the National Basic Research Program of ChinaProject(NCET-10-0278) supported by Program for New Century Excellent Talents in University,China
文摘The effect of high magnetic field on the atomic interdiffusion in Ni-Cu system was studied using the Cu/Ni/Cu diffusion couples. During the atomic interdiffusion in Ni-Cu system, it was found that the interdiffusion coefficients increased with the increase of molar fraction of Ni atoms in the interdiffusion zones when the couples were annealed with or without the magnetic field. It was noted that all corresponding interdiffusion coefficients under the magnetic field are smaller than those without the magnetic field. The results demonstrate that the magnetic field retards the atomic interdiffusion in Ni-Cu system. This retardation is achieved through reducing the frequency factors but not changing the interdiffusion activation energies.
基金Project(51175138)supported by the National Natural Science Foundation of ChinaProjects(2012HGZX0030,2013HGCH0011)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(20100111110003)supported by the Specialized Research Fund for the Doctoral Program of Higher Education,China
文摘Powder mixture of pure Al and oxidized Si C was consolidated into 10%（mass fraction） Si Cp/Al composites at 250 °C by equal channel angular pressing and torsion（ECAP-T）. The valence states of Si for Si C particulates and Al for the as-consolidated composites were detected by X-ray photoelectron spectroscopy（XPS）. The interfacial bondings of the composites were characterized by scanning electron microscopy（SEM）. The elements at the interface were linearly scanned by energy dispersive spectroscopy（EDS） and the EDS mappings of Si and Al were also obtained. The values of the nanohardness at different positions within 2 μm from the boundary of Si C particulate were measured. The results show that after ECAP-T, interfacial reaction which inhibits injurious interfacial phase occurs between Al and the oxide layer of Si C, and the element interdiffusion which can enhance interfacial bonding exists between Al and Si C. As ECAP-T passes increase, the reaction degree is intensified and the element interdiffusion layer is thickened, leading to the more smooth transition of the hardness from Si C to Al.
文摘The influence of thermal treatment on Si 1-x Ge x/Si multiple-quantum wells (MQW) p-i-n photodiodes has been investigated by photocurrent spectroscopy combined with X-ray double crystal diffraction.The cutoff wavelength is significantly reduced due to the Si-Ge interdiffusion and partial relaxation of the strained SiGe alloy.The values of the blue shift increase slowly with the annealing temperatures in the range of 750℃ to 850℃.However,the nonlinear changes in photocurrent intensities of the samples annealed at different temperatures have been observed,which is mainly dominated by the generation of misfit dislocations and the reduction of the point defects in the heating process.
文摘In the 1940s, KIRKENDALL showed that diffusion in binary solid solutions cannot be described by only one diffusion coefficient. Rather, one has to consider the diffusivity of both species. His findings changed the treatment of diffusion data and the theory of diffusion itself. A diffusion-based framework was successfully employed to explain the behaviour of the Kirkendall plane. Nonetheless, the complexity of a multiphase diffusion zone and the morphological evolution during interdiffusion requires a physico-chemical approach. The interactions in binary and more complex systems are key issues from both the fundamental and technological points of view. This paper reviews the Kirkendall effect from the circumstances of its discovery to recent developments in its understanding, with broad applicability in materials science and engineering.
基金the National Natural Science Foundation of China Nos.51671053 and 51801021the Ministry of Industry and Information Technology Project No.MJ-2017-J-99)。
文摘MCrAlY(M=Ni and/or Co)overlay coating is widely used as a protective coating against high temperature oxidation and corrosion.However,due to its big difference in chemical composition with the underlying superalloy,elements interdiffusion occurs inevitably.One of the direct results is the formation of interdiffusion zone(IDZ)and secondary reaction zone(SRZ)with a high density of fine topological closed-packed phases(TCPs),weakening dramatically the mechanical properties of the alloy substrate.It is by now the main problem of modern high-temperature metallic coatings,but there are still hardly any reports studying the formation,growth and transformation of IDZ and SRZ in deep,as well as the precipitation of TCPs.In this work,a typical NiCrAlY coating is deposited by arc ion plating on a single-crystal superalloy N5.Elements interdiffusion between them and its relationship on microstructure were clarified.Cr rather than Al from the coating diffuses into the alloy at high temperatures and segregates immediately beneath their interface,contributing largely to the formation of IDZ.Simultaneously,diffusion of Ni from the deep alloy to IDZ leads to the formation and continuous expansion of SRZ.
基金the Key-Area Research and Development Program of Guangdong Province(2019B010936001)financially supported by the National Natural Science Foundation of China(Grant Nos.51671202 and 51301184)。
文摘A low-diffusion Ni Re Pt Al coating((Ni,Pt)Al outer layer in addition to a Re-rich diffusion barrier layer)was prepared on a Ni_(3)Al-base single crystal(SC)superalloy via electroplating and gaseous aluminizing treatments,wherein the electroplating procedures consisted of the composite deposition of Ni-Re followed by electroplating of Pt.In order to perform a comparison with conventional Ni Al and(Ni,Pt)Al coatings,the cyclic oxidation performance of the Ni Re Pt Al coating was evaluated at 1100 and 1150℃.We observed that the oxidation resistance of the Ni Re Pt Al coating was significantly improved by the greater presence of the residualβ-Ni Al phase in the outer layer and the lesser outward-diffusion of Mo from the substrate.In addition,the coating with the Re-rich diffusion barrier demonstrated a lower extent of interdiffusion into the substrate,where the thickness of the second reaction zone(SRZ)in the substrate alloy decreased by 25%.The mechanisms responsible for improving the oxidation resistance and decreasing the extent of SRZ formation are discussed,in which a particular attention is paid to the inhibition of the outward diffusion of Mo by the Re-based diffusion barrier.
基金financially supported by the National Natural Science Foundation for Youth of China (No. 51701083)the Guangzhou Science and Technology Association Young Talent Lifting Project, China (No. X20210201054)+1 种基金the Open Fund of National Joint Engineering Research Center for Abrasion Control and Molding of Metal Materials, China (No. HKDNM201903)the Guangdong Basic and Applied Basic Research Foundation, China (No. 2019A1515110095)。
文摘The mechanical and diffusion properties of Ti-Ta-Fe alloys in the Ti-rich region were investigated by utilizing a high-throughput method, with the combination of nanoindentation and diffusion couple techniques.Five groups of ternary Ti-Ta-Fe diffusion couples were prepared after annealing at 1273 K for 25 h. The composition-dependent mechanical properties of bcc Ti-Ta-Fe system were experimentally determined by means of nanoindentation and electron probe microanalysis(EPMA) techniques. Moreover, the interdiffusion coefficients of Ti-Ta-Fe alloys at 1273 K were confirmed from the composition gradients of the ternary diffusion couples with the support of a pragmatic numerical inverse method. A composition-dependent database on the mechanical and diffusion properties of Ti-Ta-Fe alloys was carefully established and utilized for the discussion of the processability during the hot working. The results indicated that the content of Fe should be controlled for the Ti alloys with high hardness and low Young’s modulus.
基金the Guangdong Major Project of Basic and Applied Basic Research(No.2019B030302011)National Natural Science Foundation of China(Nos.52005523,U2032143,11902370)+3 种基金International Sci&Tech Cooperation Program of GuangDong Province(No.2019A050510022)Key Research Project of GuangDong Province(Nos.2019B010943001 and 2017B020235001)China Postdoctoral Science Foundation(Nos.2019M653173 and 2019TQ0374)the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(No.2021qntd12).
文摘High-temperature chromium(Cr)-zirconium(Zr)interdiffusion commonly occurs in Cr-coated zircaloys applied for enhanced accident-tolerant fuel(ATF)claddings.Such interdiffusion changes the interfacial microstructure and thus the fracture mechanism of the coating under external loading.In this study,the interdiffusion behavior in a magnetron sputtered Cr coating deposited on a Zr-4 alloy was studied in a vacuum environment at 1160C.In addition,the effect of interdiffusion on the microcracking behavior of the Cr coating was determined by in situ three-point bending tests.The experimental results show that the interdiffusion behavior resulted in the formation of a ZrCr2 layer,accompanied by the consumption of Cr coating and interfacial roughening.The growth of the diffusion layer followed a nearly parabolic law with respect to annealing time,and the residual stress of the annealed coating decreased with increasing annealing time.Under external loading,a large number of cracks were generated in the brittle interlayer,and some interfacial cracks were formed and grew at the ZrCr2/Zr-4 interface.Despite the remarkable microcracks in the ZrCr2 layer,the vacuum-annealed Cr coating has significantly fewer cracks than the original coating,mainly because of the recrystallization of the coating during annealing.
基金the study of volume properties of melts and density changes during the solid–liquid transition was financially supported by RFBR (Grant No. 16-38-00669)
文摘New experimental data are presented on the density and thermal expansion of solid and liquid magnesium and ultralight magnesium–lithium alloys containing 23.03 and 30.02 at.% Li, respectively. The measurements were performed using the dilatometer method and the gamma-ray attenuation technique in the temperature range from 145 to 1244 K for magnesium and from 293 to ~1000 K for the alloys. The density changes during the solid?liquid phase transition were directly measured for Mg and the Mg70Li30 alloy. The temperature dependences and reference tables of the investigated volumetric properties were developed. A comparison of the obtained results with literature data was made. The study showed that the eutectic composition in the magnesium- lithium system differs from 23 at.% Li. The concentration dependence of molar volume of the magnesium-lithium liquid system was found to be almost linear in the interval of 0-30 at.% Li and deviated noticeably from the corresponding dependence for an ideal mixture.
基金financially supported by the National Natural Science Foundation of China(No.51671053)the Natural Science Foundation of Liaoning Province of China(No.2019-ZD-0264)the Ministry of Industry and Information Technology Project(No.MJ-2017-J-99)。
文摘NiCrAlY coatings are widely applied on various alloy components to enhance oxidation and/or corrosion resistance at high temperatures.However,elements interdiffusion occurs between them due to composition difference.Although various diffusion barriers(DBs)are reported,this problem is still far from completely solved as most ceramic barriers suffer from poor adherence,while the metallic barriers play a limited role.In this study,NiCrAlY coating was deposited onto a second-generation single-crystal superalloy by arc ion plating.A novel simple method is provided to address elements interdiffusion.By pre-oxidation at a moderate temperature,a thin scale of Ni(Co)O forms at the alloy surface.It transforms to be an alumina/NiCoCr alloy/alumina sandwich by an in-situ reaction with the overlaying NiCrAlY coating and the alloy substrate at high service temperatures,which offers good barrier ability in conjunction with strong adhesion.In the presence of such an alumina/alloy/alumina DB,the NiCrAlY coating provides high resistance to oxidation and scale spallation for the alloy substrate.
基金financially supported by the National Natural Science Foundation of China (Nos.51671202 and 51301184)the "Liaoning BaiQianWan Talents" Program
文摘To refrain the interdiffusion of elements while holding good oxidation resistance,a(Ni,Pt)Al/Ni composite coating was prepared by sequential treatments of electroplating Ni and Pt and successive gaseous aluminization.In comparison with normal(Ni,Pt)Al coating,high-temperature performance of the composite coating was evaluated in isothermal oxidation test at 1100℃.Both the two coatings exhibited good resistance against high-temperature oxidation,but the interdiffusion of elements between composite coating and single-crystal(SC)superalloy substrate was greatly relieved,in which the thickness of secondary reaction zone(SRZ)and the amount of precipitated topologically close-packed phase in the SC alloy matrix were significantly decreased.Mechanisms responsible for delaying rate of coating degradation and SRZ growth/propagation are discussed.
基金National Natural Science Foundation of China (50731001, 51071013, 51001032)National Basic Research Program of China (2010CB631200)
文摘To reveal the influence of substrate/coating interdiffusion on the cyclic oxidation property of a metallic coating, cyclic oxida- tion behavior of an EB-PVD CoCrAIY coating on directionally solidified Ni-based superalloy DZ125 at 1 050℃ is investigated. The 40 μm thick CoCrA1Y coating has a cyclic oxidation life of around 160 h, and the oxidation constant is 1.915× 10^-7 mg4.cm^-8.s-1. However, severe spallation of the oxides containing Co, Cr, Ni, Ta and Ti occurs with longer cyclic oxidation. The degradation in oxidation resistance for the coating is related to the depletion of A1 due to the oxide spallation and interdiffu- sion. Severe interdiffusion between the coating and underlying substrate occurs at 1 050 ℃. The composition of the substrate has an important effect on the thermal cycling lifetime of the coating. The influencing mechanism is discussed.
