A Cr/CoNiCrAlTaY bilayer coating was prepared on the Ti-45Al-8.5Nb alloy by plasma surface metallurgy technique.The as-prepared coating with a grain size of~2μm exhibited a dense microstructure and strong adhesion du...A Cr/CoNiCrAlTaY bilayer coating was prepared on the Ti-45Al-8.5Nb alloy by plasma surface metallurgy technique.The as-prepared coating with a grain size of~2μm exhibited a dense microstructure and strong adhesion due to metallurgical bonding,consisting of outermost Cr layer and CoNiCrAlTaY transition layer.The typical power-law relationship between mass gain and time was obtained for the coated specimens with a rate exponent of 3.18 following oxidation at 1173 K.The top Cr_(2)O_(3)film and spinel oxides(i.e.,NiCr_(2)O_(4)and CoCr_(2)O_(4))exhibited a protective effect with a low oxidation reaction rate.Interfacial analysis identified Ta precipitates(Cr_(2)Ta and TaAl_(3))and Ta oxides(Ta_(2)O_(5)and Ta_(2)O_(3)),which played an essential role in retarding rapid diffusion and enhancing adhesion and oxidation resistance.展开更多
A Cr/Cr2N/CrN multilayer coating with a thickness of 24.4 μm was deposited by multi-arc ion plating. The coating was systematically characterized by field emission scanning electron microscopy(FESEM), X-ray photoelec...A Cr/Cr2N/CrN multilayer coating with a thickness of 24.4 μm was deposited by multi-arc ion plating. The coating was systematically characterized by field emission scanning electron microscopy(FESEM), X-ray photoelectron spectrometry(XPS), energy dispersive spectroscopy(EDS), X-ray diffraction(XRD) and transmission electron microscopy(TEM). Hardness and adhesion were tested by nanoindentation and scratch tester, respectively. The friction properties were investigated by a reciprocating UMT-3MT ball-on-disk tribometer in air and seawater. The results showed that the multilayer coating consisted of three different layers, with Cr,Cr2N and CrN phases, respectively. Compared with CrN single layer coating, the adhesion of the multilayer coating was improved significantly, the hardness of the multilayer coating was(21±2) GPa. The corrosion resistance of the multilayer coating was also improved in artificial seawater. The friction coefficient of multilayer coating was lower than that of CrN single layer coating both in air and seawater.展开更多
Cr/CrN multilayer coatings with bilayer periods in the range from 1351 to 260 nm were prepared on 304 stainless steel substrates by arc ion plating to study the microstructure and properties of multilayer coatings and...Cr/CrN multilayer coatings with bilayer periods in the range from 1351 to 260 nm were prepared on 304 stainless steel substrates by arc ion plating to study the microstructure and properties of multilayer coatings and stimulate their application.SEM results confirm the clear periodicity of the Cr/CrN multilayer coatings and the clear interface between individual layers.XRD patterns reveal that these multilayer coatings contain Cr,CrN and Cr_2N phases.Because Cr layer is softer than its nitride layer,the hardness decreases with the shortening of the bilayer period(or increasing volume fraction of Cr layer).The Cr/CrN multilayer coating with 862 nm period possesses the highest indentation toughness due to a proper individual Cr and nitride layer thickness.However,for the Cr/CrN multilayer with the bilayer period of 1351 nm,it possesses the lowest toughness due to more nitride phase.The indentation toughness of Cr/CrN multilayer coatings is related with their bilayer period.A coating with a proper individual Cr and nitride layer thickness possesses the highest indentation toughness.展开更多
A wear resistant （Cr, Fe）7C3/γ-Fe ceramalcomposite coating wasfabricatedon substrate of a 0.45% C carbon steel by plasma transferred arc （PTA） cladding process using the Fe-Cr-C elemental powder blends. The micro...A wear resistant （Cr, Fe）7C3/γ-Fe ceramalcomposite coating wasfabricatedon substrate of a 0.45% C carbon steel by plasma transferred arc （PTA） cladding process using the Fe-Cr-C elemental powder blends. The microstructure, microhardness and dry sliding wear resistance of the coating were evaluated. Results indicate that the plasma transferred arc clad ceramal composite coating has a rapidly solidified microstructure consisting of blocky primary （Cr, Fe）7C3 and the interblocky （ Cr, Fe）7C3/γ-Fe eutectics and is metallurgically bonded to the 0.45%C carbon steel substrate. The ceramal composite coating has high hardness and excellent wear resistance under dry sliding wear test condition.展开更多
A wear-resistant （Cr, Fe）7C3/γ-Fe in situ ceramal composite coating was fabricated on the substrate of 0.45wt%C carbon steel by a plasma-transferred arc cladding process using the Fe-Cr-C elemental powder blends. T...A wear-resistant （Cr, Fe）7C3/γ-Fe in situ ceramal composite coating was fabricated on the substrate of 0.45wt%C carbon steel by a plasma-transferred arc cladding process using the Fe-Cr-C elemental powder blends. The microstructure, microhardness, and dry-sliding wear resistance of the coating were evaluated. The results indicate that the microstructure of the coating, which was composed of （Cr, Fe）7C3 primary phase uniformly distributed in the γ-Fe, and the （Cr, Fe）7C3 eutectic matrix was metallurgically bonded to the 0.45wt%C carbon steel substrate. From substrate to coating, the microstructure of the coating exhibited an evident epitaxial growth character. The coating, indehiscent and tack-free, had high hardness and appropriate gradient. It had excellent wear resistance under the dry sliding wear test condition.展开更多
NiCr–Cr3C2 metal–ceramic composite coating is commonly produced on metal substrate by laser cladding to be used as wear-resistant coating under medium- or high-temperature working conditions.The coating has high har...NiCr–Cr3C2 metal–ceramic composite coating is commonly produced on metal substrate by laser cladding to be used as wear-resistant coating under medium- or high-temperature working conditions.The coating has high hardness, generally over three times that of the substrate.In order to make the hardness increase gradually from substrate to coating surface, the nickel-based alloy Ni45 was chosen as the transition layer and Ni Cr–Cr3C2 coating was indirectly cladded on 20Cr2Ni4 A substrate.Microstructure and composition of the coating were characterized by scanning electron microscope(SEM), energy-dispersive spectroscopy(EDS) and X-ray diffraction(XRD).Microhardness of the cross section of the coating was measured.Friction and wear behavior of Ni Cr–Cr3C2coating and substrate were investigated through sliding against the Si C ball at 20, 100 and 300 °C.The morphologies of worn surfaces were analyzed by SEM and EDS.The results show that the hardness of Ni45 transition layer is between that of the substrate and Ni Cr–Cr3C2coating, which avoids hardness jump and stress concentration of the coating.Ni Cr–Cr3C2coating contains hard phases of Cr3C2 and Cr7C3which enhance the wear resistance.With thetemperature increasing, friction coefficient and wear rate of the substrate increase significantly.Compared with the substrate, Ni Cr–Cr3C2coating has lower friction coefficient and wear rate at 100 and 300 °C, which verifies the good wear resistance of NiCr–Cr3C2 coating.展开更多
Accident tolerant fuel(ATF) for the light water reactor has gained wide attentions after the Fukushima accident. To enhance the accident-tolerance of the nuclear system, one strategy is to modify the Zr-based alloy cl...Accident tolerant fuel(ATF) for the light water reactor has gained wide attentions after the Fukushima accident. To enhance the accident-tolerance of the nuclear system, one strategy is to modify the Zr-based alloy cladding surface with advanced ceramic coating. In this work, monolithic and dense Cr_2AlC coating has been synthesized by magnetron sputtering. The as-grown Cr_2AlC coating exhibits good chemical compatibility with Zr-based alloy substrate as well as mechanical integrity under both pull-off and scratch tests. The coating system also presents moderate thermochemical compatibility at 800℃ but degrades above 1000℃ under simulated loss-of-coolant accident(LOCA) conditions.展开更多
Cr-A1-Si-N coatings were deposited on SUS 304 substrate by a hybrid coating system. A Cr interlayer was introduced between Cr-A1-Si-N coating and SUS 304 substrate to improve the coating adherence. The effects of Cr i...Cr-A1-Si-N coatings were deposited on SUS 304 substrate by a hybrid coating system. A Cr interlayer was introduced between Cr-A1-Si-N coating and SUS 304 substrate to improve the coating adherence. The effects of Cr interlayer on the microhardness, adhesion, and tribological behavior of Cr-A1-Si-N coatings were systematically investigated. The results indicate that the microhardness of the Cr-A1-Si-N coatings gradually deceases with increasing thickness of Cr interlayers. The adhesion between Cr-A1-Si-N and SUS 304 substrate is improved by addition of the Cr interlayers. A peak critical load of-50 N is observed for the coating containing Cr interlayer of 60 nm as compared - 20 N for the coating without Cr interlayer. The thicker Cr interlayers result in reduced critical load values. Moreover, the wear resistance of the Cr-AI-Si-N coatings is greatly enhanced by introducing the Cr interlayer with thickness of 60 nm in spite of the decreased microhardness. The friction coefficient of the coating system is also moderately reduced.展开更多
A new kind of multi-dimensional WC-10Co4Cr coating which is composed of nano,submicron,micron WC grains and CoCr alloy,was developed by high velocity oxy-fuel(HVOF)spraying.Porosity,microhardness,fracture toughness an...A new kind of multi-dimensional WC-10Co4Cr coating which is composed of nano,submicron,micron WC grains and CoCr alloy,was developed by high velocity oxy-fuel(HVOF)spraying.Porosity,microhardness,fracture toughness and cavitation erosion resistance of the multi-dimensional coating were investigated in comparison with the bimodal and nanostructured WC?10Co4Cr coatings.Moreover,the cavitation erosion behavior and mechanism of the multi-dimensional coating were explored.Results show that HVOF sprayed multi-dimensional WC-10Co4Cr coating possesses low porosity(≤0.32%)and high fracture toughness without obvious nano WC decarburization during spraying.Furthermore,it is discovered that the multi-dimensional WC-10Co4Cr coating exhibits the best cavitation erosion resistance which is enhanced by approximately 28%and 34%,respectively,compared with the nanostructured and bimodal coatings in fresh water.The superior cavitation resistance of multi-dimensional WC-10Co4Cr coating may originate from the unique micro?nano structure and excellent properties,which can effectively obstruct the formation and propagation of cavitation erosion cracks.展开更多
Zr/WC composite coating was prepared on the surface of Cr12MoV steel by electric spark deposition technology to change its surface properties. The surface and worn surface morphology of the coating were observed using...Zr/WC composite coating was prepared on the surface of Cr12MoV steel by electric spark deposition technology to change its surface properties. The surface and worn surface morphology of the coating were observed using scanning electron microscope. Dry friction and wear tests of the coatings were carried out at room temperature. The results show that the coating is continuous and uniform, and the thickness was about 50-60 μm. The microhardness of the coating surface was highest at 1140 HV_(200g), which was significantly higher than that of the substrate. The ear tests results show that the wear weight loss, wear volume and wear rate follow the following rules: Cr12MoV>WC coating> Zr/WC composite coating.展开更多
Pores,microcracks and density of plasma sprayed Cr2O3 coatings before and after high-intensity pulsed ion beam(HIPIB) irradiation were investigated using the ultrasonic reflection coefficient spectroscopy(URCS).The UR...Pores,microcracks and density of plasma sprayed Cr2O3 coatings before and after high-intensity pulsed ion beam(HIPIB) irradiation were investigated using the ultrasonic reflection coefficient spectroscopy(URCS).The URCS was analyzed based on an acoustic transmission model for the multi-layered structure.The longitudinal velocity in the coatings was calculated from the experimental URCS,and the attenuation coefficient expression was deduced by comparing the experimental and numerical fitting amplitude spectral lines.The longitudinal velocity of as-sprayed Cr2O3 coating is 2 002 m/s,and increases to 2 099 and 2 148 m/s after being irradiated by HIPIB with 1 and 5 shots.Correspondingly,the factor A changes from 0.046 to 0.026 and 0.020 and n from 1.702 to 1.658 and 1.649 in the attenuation coefficient expression of α=Af n.It is observed that the surface morphology of Cr2O3 coatings changes from rough and porous to smooth and uniform with the increase of shot number,which accords with the ultrasonic analyses reasonably.The URCS seems to provide a convenient and nondestructive method to characterize surface modification of the plasma sprayed coatings.展开更多
There has been much interest in developing multilayered or nanolayered physical vapor deposition（PVD） coatings identified as a group of promising protective coatings for their excellent mechanical properties and cor...There has been much interest in developing multilayered or nanolayered physical vapor deposition（PVD） coatings identified as a group of promising protective coatings for their excellent mechanical properties and corrosion resistance. In this study, the multilayered Cr N/Cr2O3 coatings with different bilayer periods（L） were synthesized on the polished high speed steel substrates from a Cr target with the alternative atmosphere of pure nitrogen and pure oxygen by arc ion plating（AIP） technique. The results revealed that the microstructure,morphologies and properties of the multilayered coatings were strongly influenced by the bilayer period（L）.There were two kinds of interfaces in the multilayered Cr N/Cr2O3coatings： the sharp ones and the blurry ones. With reducing the value of L, the macro-particles densities decreased gradually, whereas the coating microhardness, adhesive strength and wear resistance first increased, and then decreased slightly or remained stable as the bilayer period L 〈 590 nm. The multilayered Cr N/Cr2O3 coating with the bilayer period L of 590 nm possessed the best comprehensive properties, namely the highest microhardness, the strongest adhesion, and the lowest wear rate.展开更多
Cavitation erosion （CE） is the predominant cause for the failure of overflow components in fluid machinery. Advanced coatings have provided an effective solution to cavitation erosion due to the rapid development of...Cavitation erosion （CE） is the predominant cause for the failure of overflow components in fluid machinery. Advanced coatings have provided an effective solution to cavitation erosion due to the rapid development of surface engineering techniques. However, the influence of coating structures on CE resistance has not been sys- tematically studied. To better understand their relationship, micro-nano and conventional WC-10Co4Cr cermet coat- ings are deposited by high velocity oxygen fuel spray- ing（HVOF）, and their microstructures are analyzed by OM, SEM and XRD. Meanwhile, characterizations of mechan- ical and electrochemical properties of the coatings are carried out, as well as the coatings＇ resistance to CE in 3.5 wt % NaC1 solution, and the cavitation mechanisms are explored. Results show that micro-nano WC-10Co4Cr coating possesses dense microstructure, excellent mechanical and electrochemical properties, with very low porosity of 0.26 4-0.07% and extraordinary fracture toughness of 5.58 4-0.51 MPa.m1/2. Moreover, the CE resistance of micro-nano coating is enhanced above 50% than conventional coating at the steady CE period in 3.5 wt % NaC1 solution. The superior CE resistance of micro- nano WC-10Co4Cr coating may originate from the unique micro-nano structure and properties, which can effectively obstruct the formation and propagation of CE crack. Thus,a new method is proposed to enhance the CE resistance of WC-10Co4Cr coating by manipulating the microstructure.展开更多
Type Ⅰ hot corrosion behavior of SiO_2-Al_2O_3-glass composite coating based on Ti-47 Al-2 Cr-2 Nb substrate was investigated in the mixture salt of 25 wt%NaCl + 75 wt%Na_2SO_4 at 850 °C. The results showed that...Type Ⅰ hot corrosion behavior of SiO_2-Al_2O_3-glass composite coating based on Ti-47 Al-2 Cr-2 Nb substrate was investigated in the mixture salt of 25 wt%NaCl + 75 wt%Na_2SO_4 at 850 °C. The results showed that there was a bidirectional ion exchange between composite coating and the film of mixed salts, and the sodium ion in the molten salts penetrated into the glass matrix of composite coating, while the potassium ion in the glass matrix dissolved into the molten salts. A decrease in hot corrosion rate was achieved for the coated alloy in comparison with the bared substrate due to the composite coating acting as a diffusion barrier to sulfur and chlorine and preventing the molten salts from diffusing to the coating/alloy interface during the hot corrosion exposure. Additionally, the composite coating decreased the oxygen partial pressure at the coating/alloy interface and promoted the selective oxidation of Al to form a protective Al_2O_3 layer.展开更多
A series of single bcc,bcc plus fcc duplex and single fcc microcrystalline coatings of 1Cr18Ni9Ti stainless steel were prepared by using sputtering technique.The resistance against pitting corrosion was studied by mea...A series of single bcc,bcc plus fcc duplex and single fcc microcrystalline coatings of 1Cr18Ni9Ti stainless steel were prepared by using sputtering technique.The resistance against pitting corrosion was studied by measurements of pitting corrosion potentials and electrochemical noise during initiation of corrosion pits.The results show that the sputtered coatings with single bcc phase or single fcc structure are more resistant to pitting corrosion than those with bcc plus fcc duplex phase structure.展开更多
A facile ammonium-dichromate solution immersion method was introduced to synthesize the copperwettable Cr3C2 coating on and inside the carbon-carbon （C/C） preform. The formation mechanism and the microstructures of ...A facile ammonium-dichromate solution immersion method was introduced to synthesize the copperwettable Cr3C2 coating on and inside the carbon-carbon （C/C） preform. The formation mechanism and the microstructures of the Cr3C2 coatings were studied. The contact angle between molten copper and the C/C decreased from 140°to 60°, demonstrating the significant improvement in the wettability. The Cr3C2- coated C/C-Cu composite with only 4.2% porosity and 3.69 gcm^-3 density was manufactured through copper infiltration. As a result, the thermal and electrical conductivity of the modified C/C-Cu increased significantly due to the infiltrated copper. Also the mechanical properties of the composites including both the flexural and compressive strengths were enhanced by over 100%. The modified C/C-Cu composite exhibited lower friction coefficients and wear rates for different load levels than those of the commercial C/Cu composite. These results demonstrate the potential of the modified C/C-Cu material for use in electrical contacts.展开更多
Micrometer and nanometer Cr particles were co-deposited with Ni by electroplating from a nickel sulfate bath containing a certain content of Cr particles. Cr microparticles are in a size range of 1-5 μm and Cr nanopa...Micrometer and nanometer Cr particles were co-deposited with Ni by electroplating from a nickel sulfate bath containing a certain content of Cr particles. Cr microparticles are in a size range of 1-5 μm and Cr nanoparticles have an average size of 40 nm. The friction and the wear performance of the co-deposited Ni-Cr composite coatings were comparatively evaluated by sliding against Si3N4 ceramic balls under non-lubricated conditions. It is found that the incorporation of Cr particles enhances the microhardness and wear resistance of Ni coatings. The wear resistance of Ni composite coating containing Cr nanoparticles is higher than that of the Ni composite coating containing Cr microparticles with a comparable Cr particle content. The co-deposition of smaller nanometer Cr particles with Ni effectively reduces the size of Ni crystals and significantly increases the hardness of the composite coatings due to grain-refinement strengthening and dispersion-strengthening,resulting in a significant improvement of wear resistance of the Ni-Cr nanocomposite coatings.展开更多
Cr1-xAlxN coatings have been deposited on a Ti3Al based alloy by reactive sputtering method. The results of the isothermal oxidation test at 800-900℃ showed that Cr1-xAlxN coatings could remarkably reduce the oxidati...Cr1-xAlxN coatings have been deposited on a Ti3Al based alloy by reactive sputtering method. The results of the isothermal oxidation test at 800-900℃ showed that Cr1-xAlxN coatings could remarkably reduce the oxidation rate of the alloy owing to the formation of Al2O3＋Cr2O3 mixture oxide scale on the surface of the coatings. No spallation of the coatings or oxide scales took place during the cyclic oxidation at 800℃. Ti was observed to diffuse into the coatings, the diffusion distance of which was very short, and the diffusion ability of it was proportional to the AI content in the coatings. Compared to Ti, Nb can diffuse much more easily through the whole coatings and oxide scales.展开更多
In this study, CrN/Cr2O3 double-layered coatings with various thickness ratios of CrN vs Cr2O3 layer were prepared by arc ion plating technology. The influences of the thickness ratio of CrN vs Cr2O3 layer on the micr...In this study, CrN/Cr2O3 double-layered coatings with various thickness ratios of CrN vs Cr2O3 layer were prepared by arc ion plating technology. The influences of the thickness ratio of CrN vs Cr2O3 layer on the microstructural characteristics as well as the mechanical and tribological properties of the CrN/Cr2O3 doublelayered coatings were investigated. The corresponding mechanisms were also discussed. The results indicated that the insertion of CrN layer between the Cr2O3 layer and substrate can effectively decrease the internal stress level of the coating. With increasing the thickness ratio of CrN vs Cr2O3 layer, the surface roughness of double-layered coatings decreased gradually, which had a certain influence on the friction coefficient. In addition, the microhardness also declined gradually, the adhesive strength almost increased linearly, whereas the wear rate declined firstly and then increased slightly. As the thickness ratio was 2：1, the double-layered coating exhibited the best wear resistance.展开更多
Zn-Cr coating was prepared on the surface of sintered NdFeB permanent magnet samples and preparation parameters were established. The anticorrosive property of Zn-Cr coating on NdFeB was studied by whole-immersion tes...Zn-Cr coating was prepared on the surface of sintered NdFeB permanent magnet samples and preparation parameters were established. The anticorrosive property of Zn-Cr coating on NdFeB was studied by whole-immersion test in NaCl solution and compared with that of zinc plating and nickel plating on NdFeB. Open-circuit potential and self-corrosion current of NdFeB samples with and without Zn-Cr coating were measured. The micro-morphology and composition of Zn-Cr coming were analyzed through SEM, XPS, EDS and XRD. The effect of Zn-Cr coating on magnetic property of NdFeB magnet was also investigated. It is exposed that Zn-Cr coating is anodic type coating for NdFeB magnet, and provided substrate electrochemical protection, barrier protection and passivation protection. The anticorrosion property of NdFeB magnet is obviously enhanced by Zn-Cr coating while the magnet property of NdFeB magnet changed little.展开更多
基金financial supports from Shanxi Provincial Natural Science Foundation,China(No.20210302123162)Shanxi Scholarship Council of China(No.2024-057)+2 种基金State Key Laboratory of Advanced Metal Materials,China(No.2019-ZD02)Science and Technology Achievement Transformation and Cultivation Project of Shanxi,China(No.2020CG011)Shanxi“1331 Project”Quality Improvement and Efficiency Project,China。
文摘A Cr/CoNiCrAlTaY bilayer coating was prepared on the Ti-45Al-8.5Nb alloy by plasma surface metallurgy technique.The as-prepared coating with a grain size of~2μm exhibited a dense microstructure and strong adhesion due to metallurgical bonding,consisting of outermost Cr layer and CoNiCrAlTaY transition layer.The typical power-law relationship between mass gain and time was obtained for the coated specimens with a rate exponent of 3.18 following oxidation at 1173 K.The top Cr_(2)O_(3)film and spinel oxides(i.e.,NiCr_(2)O_(4)and CoCr_(2)O_(4))exhibited a protective effect with a low oxidation reaction rate.Interfacial analysis identified Ta precipitates(Cr_(2)Ta and TaAl_(3))and Ta oxides(Ta_(2)O_(5)and Ta_(2)O_(3)),which played an essential role in retarding rapid diffusion and enhancing adhesion and oxidation resistance.
基金Project(51475449)supported by the National Natural Science Foundation of China
文摘A Cr/Cr2N/CrN multilayer coating with a thickness of 24.4 μm was deposited by multi-arc ion plating. The coating was systematically characterized by field emission scanning electron microscopy(FESEM), X-ray photoelectron spectrometry(XPS), energy dispersive spectroscopy(EDS), X-ray diffraction(XRD) and transmission electron microscopy(TEM). Hardness and adhesion were tested by nanoindentation and scratch tester, respectively. The friction properties were investigated by a reciprocating UMT-3MT ball-on-disk tribometer in air and seawater. The results showed that the multilayer coating consisted of three different layers, with Cr,Cr2N and CrN phases, respectively. Compared with CrN single layer coating, the adhesion of the multilayer coating was improved significantly, the hardness of the multilayer coating was(21±2) GPa. The corrosion resistance of the multilayer coating was also improved in artificial seawater. The friction coefficient of multilayer coating was lower than that of CrN single layer coating both in air and seawater.
基金Project(51171118)supported by the National Natural Science Foundation of ChinaProject(2012-4)supported by the Liaoning Provincial Key Laboratory of Advanced Materials,Shenyang University,China
文摘Cr/CrN multilayer coatings with bilayer periods in the range from 1351 to 260 nm were prepared on 304 stainless steel substrates by arc ion plating to study the microstructure and properties of multilayer coatings and stimulate their application.SEM results confirm the clear periodicity of the Cr/CrN multilayer coatings and the clear interface between individual layers.XRD patterns reveal that these multilayer coatings contain Cr,CrN and Cr_2N phases.Because Cr layer is softer than its nitride layer,the hardness decreases with the shortening of the bilayer period(or increasing volume fraction of Cr layer).The Cr/CrN multilayer coating with 862 nm period possesses the highest indentation toughness due to a proper individual Cr and nitride layer thickness.However,for the Cr/CrN multilayer with the bilayer period of 1351 nm,it possesses the lowest toughness due to more nitride phase.The indentation toughness of Cr/CrN multilayer coatings is related with their bilayer period.A coating with a proper individual Cr and nitride layer thickness possesses the highest indentation toughness.
文摘A wear resistant （Cr, Fe）7C3/γ-Fe ceramalcomposite coating wasfabricatedon substrate of a 0.45% C carbon steel by plasma transferred arc （PTA） cladding process using the Fe-Cr-C elemental powder blends. The microstructure, microhardness and dry sliding wear resistance of the coating were evaluated. Results indicate that the plasma transferred arc clad ceramal composite coating has a rapidly solidified microstructure consisting of blocky primary （Cr, Fe）7C3 and the interblocky （ Cr, Fe）7C3/γ-Fe eutectics and is metallurgically bonded to the 0.45%C carbon steel substrate. The ceramal composite coating has high hardness and excellent wear resistance under dry sliding wear test condition.
文摘A wear-resistant （Cr, Fe）7C3/γ-Fe in situ ceramal composite coating was fabricated on the substrate of 0.45wt%C carbon steel by a plasma-transferred arc cladding process using the Fe-Cr-C elemental powder blends. The microstructure, microhardness, and dry-sliding wear resistance of the coating were evaluated. The results indicate that the microstructure of the coating, which was composed of （Cr, Fe）7C3 primary phase uniformly distributed in the γ-Fe, and the （Cr, Fe）7C3 eutectic matrix was metallurgically bonded to the 0.45wt%C carbon steel substrate. From substrate to coating, the microstructure of the coating exhibited an evident epitaxial growth character. The coating, indehiscent and tack-free, had high hardness and appropriate gradient. It had excellent wear resistance under the dry sliding wear test condition.
基金financially supported by the National Natural Science Foundation of China (No. 51275020)the National Defense Pre-Research Foundation of China (No. 9140A18020212HK01210)
文摘NiCr–Cr3C2 metal–ceramic composite coating is commonly produced on metal substrate by laser cladding to be used as wear-resistant coating under medium- or high-temperature working conditions.The coating has high hardness, generally over three times that of the substrate.In order to make the hardness increase gradually from substrate to coating surface, the nickel-based alloy Ni45 was chosen as the transition layer and Ni Cr–Cr3C2 coating was indirectly cladded on 20Cr2Ni4 A substrate.Microstructure and composition of the coating were characterized by scanning electron microscope(SEM), energy-dispersive spectroscopy(EDS) and X-ray diffraction(XRD).Microhardness of the cross section of the coating was measured.Friction and wear behavior of Ni Cr–Cr3C2coating and substrate were investigated through sliding against the Si C ball at 20, 100 and 300 °C.The morphologies of worn surfaces were analyzed by SEM and EDS.The results show that the hardness of Ni45 transition layer is between that of the substrate and Ni Cr–Cr3C2coating, which avoids hardness jump and stress concentration of the coating.Ni Cr–Cr3C2coating contains hard phases of Cr3C2 and Cr7C3which enhance the wear resistance.With thetemperature increasing, friction coefficient and wear rate of the substrate increase significantly.Compared with the substrate, Ni Cr–Cr3C2coating has lower friction coefficient and wear rate at 100 and 300 °C, which verifies the good wear resistance of NiCr–Cr3C2 coating.
基金supported by the National Natural Science Foundation of China under Grant Nos. 51402311 and 51772302the National Key R&D Program of China under Grant No. 2017YFB0703201
文摘Accident tolerant fuel(ATF) for the light water reactor has gained wide attentions after the Fukushima accident. To enhance the accident-tolerance of the nuclear system, one strategy is to modify the Zr-based alloy cladding surface with advanced ceramic coating. In this work, monolithic and dense Cr_2AlC coating has been synthesized by magnetron sputtering. The as-grown Cr_2AlC coating exhibits good chemical compatibility with Zr-based alloy substrate as well as mechanical integrity under both pull-off and scratch tests. The coating system also presents moderate thermochemical compatibility at 800℃ but degrades above 1000℃ under simulated loss-of-coolant accident(LOCA) conditions.
基金supported by a grant from the National Core Research Center (NCRC) Program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (No. 2010-0001-226)a grant from the Fundamental R&D Program for Core Technology of Materials funded by the Ministry of Knowledge Economy, Republic of Korea
文摘Cr-A1-Si-N coatings were deposited on SUS 304 substrate by a hybrid coating system. A Cr interlayer was introduced between Cr-A1-Si-N coating and SUS 304 substrate to improve the coating adherence. The effects of Cr interlayer on the microhardness, adhesion, and tribological behavior of Cr-A1-Si-N coatings were systematically investigated. The results indicate that the microhardness of the Cr-A1-Si-N coatings gradually deceases with increasing thickness of Cr interlayers. The adhesion between Cr-A1-Si-N and SUS 304 substrate is improved by addition of the Cr interlayers. A peak critical load of-50 N is observed for the coating containing Cr interlayer of 60 nm as compared - 20 N for the coating without Cr interlayer. The thicker Cr interlayers result in reduced critical load values. Moreover, the wear resistance of the Cr-AI-Si-N coatings is greatly enhanced by introducing the Cr interlayer with thickness of 60 nm in spite of the decreased microhardness. The friction coefficient of the coating system is also moderately reduced.
基金Projects(51422507,51379168)supported by the National Natural Science Foundation of China
文摘A new kind of multi-dimensional WC-10Co4Cr coating which is composed of nano,submicron,micron WC grains and CoCr alloy,was developed by high velocity oxy-fuel(HVOF)spraying.Porosity,microhardness,fracture toughness and cavitation erosion resistance of the multi-dimensional coating were investigated in comparison with the bimodal and nanostructured WC?10Co4Cr coatings.Moreover,the cavitation erosion behavior and mechanism of the multi-dimensional coating were explored.Results show that HVOF sprayed multi-dimensional WC-10Co4Cr coating possesses low porosity(≤0.32%)and high fracture toughness without obvious nano WC decarburization during spraying.Furthermore,it is discovered that the multi-dimensional WC-10Co4Cr coating exhibits the best cavitation erosion resistance which is enhanced by approximately 28%and 34%,respectively,compared with the nanostructured and bimodal coatings in fresh water.The superior cavitation resistance of multi-dimensional WC-10Co4Cr coating may originate from the unique micro?nano structure and excellent properties,which can effectively obstruct the formation and propagation of cavitation erosion cracks.
基金supported by Key Projects of Strategic International Scientific and Technological Innovation Cooperation(Grant No.2016YFE0201300)
文摘Zr/WC composite coating was prepared on the surface of Cr12MoV steel by electric spark deposition technology to change its surface properties. The surface and worn surface morphology of the coating were observed using scanning electron microscope. Dry friction and wear tests of the coatings were carried out at room temperature. The results show that the coating is continuous and uniform, and the thickness was about 50-60 μm. The microhardness of the coating surface was highest at 1140 HV_(200g), which was significantly higher than that of the substrate. The ear tests results show that the wear weight loss, wear volume and wear rate follow the following rules: Cr12MoV>WC coating> Zr/WC composite coating.
基金Project(KM200710015010) supported by the Scientific Research Program of Beijing Municipal Education Commission,China
文摘Pores,microcracks and density of plasma sprayed Cr2O3 coatings before and after high-intensity pulsed ion beam(HIPIB) irradiation were investigated using the ultrasonic reflection coefficient spectroscopy(URCS).The URCS was analyzed based on an acoustic transmission model for the multi-layered structure.The longitudinal velocity in the coatings was calculated from the experimental URCS,and the attenuation coefficient expression was deduced by comparing the experimental and numerical fitting amplitude spectral lines.The longitudinal velocity of as-sprayed Cr2O3 coating is 2 002 m/s,and increases to 2 099 and 2 148 m/s after being irradiated by HIPIB with 1 and 5 shots.Correspondingly,the factor A changes from 0.046 to 0.026 and 0.020 and n from 1.702 to 1.658 and 1.649 in the attenuation coefficient expression of α=Af n.It is observed that the surface morphology of Cr2O3 coatings changes from rough and porous to smooth and uniform with the increase of shot number,which accords with the ultrasonic analyses reasonably.The URCS seems to provide a convenient and nondestructive method to characterize surface modification of the plasma sprayed coatings.
基金financial supports from the National Key Basic Research Program of China (973 Program, No. 2012CB625100)the National Natural Science Foundation of China (Nos. 51001106 and 51301181)the Doctoral Starting up Foundation of Liaoning Province Science and Technology Agency, China (No. 20131118)
文摘There has been much interest in developing multilayered or nanolayered physical vapor deposition（PVD） coatings identified as a group of promising protective coatings for their excellent mechanical properties and corrosion resistance. In this study, the multilayered Cr N/Cr2O3 coatings with different bilayer periods（L） were synthesized on the polished high speed steel substrates from a Cr target with the alternative atmosphere of pure nitrogen and pure oxygen by arc ion plating（AIP） technique. The results revealed that the microstructure,morphologies and properties of the multilayered coatings were strongly influenced by the bilayer period（L）.There were two kinds of interfaces in the multilayered Cr N/Cr2O3coatings： the sharp ones and the blurry ones. With reducing the value of L, the macro-particles densities decreased gradually, whereas the coating microhardness, adhesive strength and wear resistance first increased, and then decreased slightly or remained stable as the bilayer period L 〈 590 nm. The multilayered Cr N/Cr2O3 coating with the bilayer period L of 590 nm possessed the best comprehensive properties, namely the highest microhardness, the strongest adhesion, and the lowest wear rate.
基金Supported by National Natural Science Foundation of China (Grand No. 51422507)
文摘Cavitation erosion （CE） is the predominant cause for the failure of overflow components in fluid machinery. Advanced coatings have provided an effective solution to cavitation erosion due to the rapid development of surface engineering techniques. However, the influence of coating structures on CE resistance has not been sys- tematically studied. To better understand their relationship, micro-nano and conventional WC-10Co4Cr cermet coat- ings are deposited by high velocity oxygen fuel spray- ing（HVOF）, and their microstructures are analyzed by OM, SEM and XRD. Meanwhile, characterizations of mechan- ical and electrochemical properties of the coatings are carried out, as well as the coatings＇ resistance to CE in 3.5 wt % NaC1 solution, and the cavitation mechanisms are explored. Results show that micro-nano WC-10Co4Cr coating possesses dense microstructure, excellent mechanical and electrochemical properties, with very low porosity of 0.26 4-0.07% and extraordinary fracture toughness of 5.58 4-0.51 MPa.m1/2. Moreover, the CE resistance of micro-nano coating is enhanced above 50% than conventional coating at the steady CE period in 3.5 wt % NaC1 solution. The superior CE resistance of micro- nano WC-10Co4Cr coating may originate from the unique micro-nano structure and properties, which can effectively obstruct the formation and propagation of CE crack. Thus,a new method is proposed to enhance the CE resistance of WC-10Co4Cr coating by manipulating the microstructure.
基金supported by the National Natural Science Foundation of China (Grant No. 51201171)the National High Technology Research and Development Program of China (863 Program, Grant No. 2012AA03A512)
文摘Type Ⅰ hot corrosion behavior of SiO_2-Al_2O_3-glass composite coating based on Ti-47 Al-2 Cr-2 Nb substrate was investigated in the mixture salt of 25 wt%NaCl + 75 wt%Na_2SO_4 at 850 °C. The results showed that there was a bidirectional ion exchange between composite coating and the film of mixed salts, and the sodium ion in the molten salts penetrated into the glass matrix of composite coating, while the potassium ion in the glass matrix dissolved into the molten salts. A decrease in hot corrosion rate was achieved for the coated alloy in comparison with the bared substrate due to the composite coating acting as a diffusion barrier to sulfur and chlorine and preventing the molten salts from diffusing to the coating/alloy interface during the hot corrosion exposure. Additionally, the composite coating decreased the oxygen partial pressure at the coating/alloy interface and promoted the selective oxidation of Al to form a protective Al_2O_3 layer.
文摘A series of single bcc,bcc plus fcc duplex and single fcc microcrystalline coatings of 1Cr18Ni9Ti stainless steel were prepared by using sputtering technique.The resistance against pitting corrosion was studied by measurements of pitting corrosion potentials and electrochemical noise during initiation of corrosion pits.The results show that the sputtered coatings with single bcc phase or single fcc structure are more resistant to pitting corrosion than those with bcc plus fcc duplex phase structure.
基金the financial support from of the National Basic Research Program of China (Nos. 2012CB619600 and 2011CB012803)
文摘A facile ammonium-dichromate solution immersion method was introduced to synthesize the copperwettable Cr3C2 coating on and inside the carbon-carbon （C/C） preform. The formation mechanism and the microstructures of the Cr3C2 coatings were studied. The contact angle between molten copper and the C/C decreased from 140°to 60°, demonstrating the significant improvement in the wettability. The Cr3C2- coated C/C-Cu composite with only 4.2% porosity and 3.69 gcm^-3 density was manufactured through copper infiltration. As a result, the thermal and electrical conductivity of the modified C/C-Cu increased significantly due to the infiltrated copper. Also the mechanical properties of the composites including both the flexural and compressive strengths were enhanced by over 100%. The modified C/C-Cu composite exhibited lower friction coefficients and wear rates for different load levels than those of the commercial C/Cu composite. These results demonstrate the potential of the modified C/C-Cu material for use in electrical contacts.
基金Project(9951Z012) supported by the Major Programs of the Heilongjiang Provincial Education Department, ChinaProject(11531319) supported by the Scientific Research Fund of Heilongjiang Provincial Education Department, ChinaProject(06-13) supported by the Scientific Research Startup Foundation of Heilongjiang Institute of Science and Technology, China
文摘Micrometer and nanometer Cr particles were co-deposited with Ni by electroplating from a nickel sulfate bath containing a certain content of Cr particles. Cr microparticles are in a size range of 1-5 μm and Cr nanoparticles have an average size of 40 nm. The friction and the wear performance of the co-deposited Ni-Cr composite coatings were comparatively evaluated by sliding against Si3N4 ceramic balls under non-lubricated conditions. It is found that the incorporation of Cr particles enhances the microhardness and wear resistance of Ni coatings. The wear resistance of Ni composite coating containing Cr nanoparticles is higher than that of the Ni composite coating containing Cr microparticles with a comparable Cr particle content. The co-deposition of smaller nanometer Cr particles with Ni effectively reduces the size of Ni crystals and significantly increases the hardness of the composite coatings due to grain-refinement strengthening and dispersion-strengthening,resulting in a significant improvement of wear resistance of the Ni-Cr nanocomposite coatings.
基金the National Natural Science Foundation of China under grant Nos. 50371095 , 50571106.
文摘Cr1-xAlxN coatings have been deposited on a Ti3Al based alloy by reactive sputtering method. The results of the isothermal oxidation test at 800-900℃ showed that Cr1-xAlxN coatings could remarkably reduce the oxidation rate of the alloy owing to the formation of Al2O3＋Cr2O3 mixture oxide scale on the surface of the coatings. No spallation of the coatings or oxide scales took place during the cyclic oxidation at 800℃. Ti was observed to diffuse into the coatings, the diffusion distance of which was very short, and the diffusion ability of it was proportional to the AI content in the coatings. Compared to Ti, Nb can diffuse much more easily through the whole coatings and oxide scales.
基金the National Key Basic Research Program of China("973 Program",No.2012CB625100)the National Natural Science Foundation of China(No.51001106&No.51301181)the Doctoral Starting up Foundation of Liaoning Province Science and Technology Agency,China(No.20131118)
文摘In this study, CrN/Cr2O3 double-layered coatings with various thickness ratios of CrN vs Cr2O3 layer were prepared by arc ion plating technology. The influences of the thickness ratio of CrN vs Cr2O3 layer on the microstructural characteristics as well as the mechanical and tribological properties of the CrN/Cr2O3 doublelayered coatings were investigated. The corresponding mechanisms were also discussed. The results indicated that the insertion of CrN layer between the Cr2O3 layer and substrate can effectively decrease the internal stress level of the coating. With increasing the thickness ratio of CrN vs Cr2O3 layer, the surface roughness of double-layered coatings decreased gradually, which had a certain influence on the friction coefficient. In addition, the microhardness also declined gradually, the adhesive strength almost increased linearly, whereas the wear rate declined firstly and then increased slightly. As the thickness ratio was 2：1, the double-layered coating exhibited the best wear resistance.
文摘Zn-Cr coating was prepared on the surface of sintered NdFeB permanent magnet samples and preparation parameters were established. The anticorrosive property of Zn-Cr coating on NdFeB was studied by whole-immersion test in NaCl solution and compared with that of zinc plating and nickel plating on NdFeB. Open-circuit potential and self-corrosion current of NdFeB samples with and without Zn-Cr coating were measured. The micro-morphology and composition of Zn-Cr coming were analyzed through SEM, XPS, EDS and XRD. The effect of Zn-Cr coating on magnetic property of NdFeB magnet was also investigated. It is exposed that Zn-Cr coating is anodic type coating for NdFeB magnet, and provided substrate electrochemical protection, barrier protection and passivation protection. The anticorrosion property of NdFeB magnet is obviously enhanced by Zn-Cr coating while the magnet property of NdFeB magnet changed little.
