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
Al2O3-13%TiO2 （mass fraction） coatings, prepared by laser cladding on nickel-based alloy, were heated using high frequency induction sources. The coating microstructure and the interface between bond coating and cer...Al2O3-13%TiO2 （mass fraction） coatings, prepared by laser cladding on nickel-based alloy, were heated using high frequency induction sources. The coating microstructure and the interface between bond coating and ceramic coating were characterized by SEM, XRD and EDS. The results show that two-layer substructure exists in the ceramic coating： one layer evolving from fully melted region where the sintered grains grow fully; another layer resembling the liquid-phase-sintered structure consisting of three-dimensional net where the melted Al2O3 particles are embedded in the TiO2-rich matrix. The mechanism of the two-layer substructure formation is also explained in terms of the melting and flattening behavior of the powders during laser cladding processing. The spinel compounds NiAl2O4 and acicular compounds Cr2O3 are discovered in the interface between bond coating and ceramic coating. It proves that the chemical reactions in the laser cladding process will significantly enhance the coating adhesion.展开更多
To improve the wear resistance and corrosion resistance of magnesium alloys, a 5 kW continuous wave CO2 laser was used to investigate the laser surface cladding on AZ31 B magnesium alloys with Al-Si/Al2O3-TiO2 composi...To improve the wear resistance and corrosion resistance of magnesium alloys, a 5 kW continuous wave CO2 laser was used to investigate the laser surface cladding on AZ31 B magnesium alloys with Al-Si/Al2O3-TiO2 composite powders. A detailed microstructure, chemical composition, and phase analysis of the composite coatings were studied by scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, and X-ray diffraction （XRD）. The laser cladding shows good metallurgical bonding with the substrate. The composite coatings are composed of Mgl7Al12, Al3Mg2, Mg2Si, Al2O3, and TiO2 phases. Compared to the average microhardness （50HV0.05） of the AZ3 1 B substrate, that of the composite coatings （230HV0.05） is improved significantly. The wear resistances of the surface layers were evaluated in detail. The results demonstrate that the wear resistances of the laser surface-modified samples are considerably improved compared to the substrate. It also show that the composite coatings exhibit better corrosion resistance than that of the substrate in 3.5wt% NaCI solution.展开更多
A newly developed method is introduced for producing Cr 2O 3 base ceramic coating on aluminum alloys. On the basis of properly selecting base reactions, slurry is prepared and then applied onto the substrate surface...A newly developed method is introduced for producing Cr 2O 3 base ceramic coating on aluminum alloys. On the basis of properly selecting base reactions, slurry is prepared and then applied onto the substrate surface. By chemical reactions taken place in situ on the surface of aluminum alloy at relative low temperature, Cr 2O 3 base ceramic coating is formed. By means of scanning electron microscopy, the coating microstructure and the bonding mechanism are studied. X ray diffraction analysis is also used to investigate the chemical composition of the coating. The coating formation mechanism is further discussed. With a pin on disk tester, wear test is made to evaluate the wear performances of the coating. The results show that by applying the coating on aluminum alloy, the wear decreases 5 times in comparation to that without coating.展开更多
Cr 2 O 3-coated LiNi 1/3 Co 1/3 Mn 1/3 O 2 cathode materials were synthesized by a novel method. The structure and electrochemical properties of prepared cathode materials were measured using X-ray diffraction (XRD), ...Cr 2 O 3-coated LiNi 1/3 Co 1/3 Mn 1/3 O 2 cathode materials were synthesized by a novel method. The structure and electrochemical properties of prepared cathode materials were measured using X-ray diffraction (XRD), scanning electron microscopy (SEM), charge-discharge tests, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The measured results indicate that surface coating with 1.0 wt% Cr 2 O 3 does not affect the LiNi 1/3 Co 1/3 Mn 1/3 O 2 crystal structure (α-NaFeO 2 ) of the cathode material compared to the pristine material, the surfaces of LiNi 1/3 Co 1/3 Mn 1/3 O 2 samples are covered with Cr 2 O 3 well, and the LiNi 1/3 Co 1/3 Mn 1/3 O 2 material coated with Cr 2 O 3 has better electrochemical performance under a high cutoff voltage of 4.5 V. Moreover, at room temperature, the initial discharging capacity of LiNi 1/3 Co 1/3 Mn 1/3 O 2 material coated with 1.0 wt.% Cr 2 O 3 at 0.5C reaches 169 mAh·g 1 and the capacity retention is 83.1% after 30 cycles, while that of the bare LiNi 1/3 Co 1/3 Mn 1/3 O 2 is only 160.8 mAh·g 1 and 72.5%. Finally, the coated samples are found to display the improved electrochemical performance, which is mainly attributed to the suppression of the charge-transfer resistance at the interface between the cathode and the electrolyte.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
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
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Project (59975046) supported by the National Natural Science Foundation of China
文摘Al2O3-13%TiO2 （mass fraction） coatings, prepared by laser cladding on nickel-based alloy, were heated using high frequency induction sources. The coating microstructure and the interface between bond coating and ceramic coating were characterized by SEM, XRD and EDS. The results show that two-layer substructure exists in the ceramic coating： one layer evolving from fully melted region where the sintered grains grow fully; another layer resembling the liquid-phase-sintered structure consisting of three-dimensional net where the melted Al2O3 particles are embedded in the TiO2-rich matrix. The mechanism of the two-layer substructure formation is also explained in terms of the melting and flattening behavior of the powders during laser cladding processing. The spinel compounds NiAl2O4 and acicular compounds Cr2O3 are discovered in the interface between bond coating and ceramic coating. It proves that the chemical reactions in the laser cladding process will significantly enhance the coating adhesion.
基金Funded by the national Natural Science Foundation of China (No. 51075293)the Foundation for Development of Science and Technology of Taiyuan University of Technology,China(No.K201014)
文摘To improve the wear resistance and corrosion resistance of magnesium alloys, a 5 kW continuous wave CO2 laser was used to investigate the laser surface cladding on AZ31 B magnesium alloys with Al-Si/Al2O3-TiO2 composite powders. A detailed microstructure, chemical composition, and phase analysis of the composite coatings were studied by scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, and X-ray diffraction （XRD）. The laser cladding shows good metallurgical bonding with the substrate. The composite coatings are composed of Mgl7Al12, Al3Mg2, Mg2Si, Al2O3, and TiO2 phases. Compared to the average microhardness （50HV0.05） of the AZ3 1 B substrate, that of the composite coatings （230HV0.05） is improved significantly. The wear resistances of the surface layers were evaluated in detail. The results demonstrate that the wear resistances of the laser surface-modified samples are considerably improved compared to the substrate. It also show that the composite coatings exhibit better corrosion resistance than that of the substrate in 3.5wt% NaCI solution.
文摘A newly developed method is introduced for producing Cr 2O 3 base ceramic coating on aluminum alloys. On the basis of properly selecting base reactions, slurry is prepared and then applied onto the substrate surface. By chemical reactions taken place in situ on the surface of aluminum alloy at relative low temperature, Cr 2O 3 base ceramic coating is formed. By means of scanning electron microscopy, the coating microstructure and the bonding mechanism are studied. X ray diffraction analysis is also used to investigate the chemical composition of the coating. The coating formation mechanism is further discussed. With a pin on disk tester, wear test is made to evaluate the wear performances of the coating. The results show that by applying the coating on aluminum alloy, the wear decreases 5 times in comparation to that without coating.
基金supported by the National Key Project for Basic Research of China (No. 2005CB623605)the National Natural Science Foundation of China (No. 11074039)the National Science Foundation for Young Scholars (No.11004032)
文摘Cr 2 O 3-coated LiNi 1/3 Co 1/3 Mn 1/3 O 2 cathode materials were synthesized by a novel method. The structure and electrochemical properties of prepared cathode materials were measured using X-ray diffraction (XRD), scanning electron microscopy (SEM), charge-discharge tests, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The measured results indicate that surface coating with 1.0 wt% Cr 2 O 3 does not affect the LiNi 1/3 Co 1/3 Mn 1/3 O 2 crystal structure (α-NaFeO 2 ) of the cathode material compared to the pristine material, the surfaces of LiNi 1/3 Co 1/3 Mn 1/3 O 2 samples are covered with Cr 2 O 3 well, and the LiNi 1/3 Co 1/3 Mn 1/3 O 2 material coated with Cr 2 O 3 has better electrochemical performance under a high cutoff voltage of 4.5 V. Moreover, at room temperature, the initial discharging capacity of LiNi 1/3 Co 1/3 Mn 1/3 O 2 material coated with 1.0 wt.% Cr 2 O 3 at 0.5C reaches 169 mAh·g 1 and the capacity retention is 83.1% after 30 cycles, while that of the bare LiNi 1/3 Co 1/3 Mn 1/3 O 2 is only 160.8 mAh·g 1 and 72.5%. Finally, the coated samples are found to display the improved electrochemical performance, which is mainly attributed to the suppression of the charge-transfer resistance at the interface between the cathode and the electrolyte.
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.
