Calcium phosphate(CaP) coatings were prepared on Mg–8Li–2Ca magnesium alloy by micro-arc oxidation(MAO) in an alkaline Na_3PO_4–Ca[C_3H_7O_6P] base solution at the different applied voltages. Scanning electron micr...Calcium phosphate(CaP) coatings were prepared on Mg–8Li–2Ca magnesium alloy by micro-arc oxidation(MAO) in an alkaline Na_3PO_4–Ca[C_3H_7O_6P] base solution at the different applied voltages. Scanning electron microscope and X-ray diffraction were employed to characterize the microstructure and phase composition of the coatings, respectively. The corrosion resistance of the coatings was assessed by potential dynamic polarization curves, electrochemical impedance spectroscopy and hydrogen evolution experiment in simulated body fluids solution. The friction and wear properties were evaluated by friction and wear testing machine. The results demonstrate that the coating surface is porous and mainly composed of MgO, Ca_5(PO_4)_3(OH) and CaH_2P_2O_5. With the increase in voltage, the corrosion resistance and wear resistance of the MAO coating are both enhanced. The corrosion current density of the MAO coating decreases about two orders of the magnitude compared to the substrate. Additionally, wear and corrosion mechanisms are discussed.展开更多
Prior studies have noted that gas nitriding has a considerable effect for wear resistance. The aim of this paper is to study the influence of gas nitriding time (12, 24, 36 and 48 h) in the wear behaviour of 42CrMo4 s...Prior studies have noted that gas nitriding has a considerable effect for wear resistance. The aim of this paper is to study the influence of gas nitriding time (12, 24, 36 and 48 h) in the wear behaviour of 42CrMo4 steel. It has been assessed by micro hardness, pin-on-disc tribosystem, and SEM through the nitrided layer for each nitriding time. The study relates to the performance of the compound layer and the diffusion layer with respect to adhesive wear. The results were analyzed in terms of the weight lost during wear, for nitrided steel with and without the compound layer, and for untreated steel. It has been observed that wear rate varies as a function of the tests conditions due to the presence of different wear mechanisms. Thus, for short tests conditions wear rate depends on two mechanisms: plastic deformation and adhesive wear, whereas for large tests conditions the mechanisms controlling wear rate are abrasive and oxidative wear. Furthermore, this study contains an analysis of the wear mechanisms of a nitrided part, founded on scanning electron microscopy (SEM) observations of the wear traces at various stages of the evolution of wear. The SEM examination of worn surfaces revealed signatures for the adhesion, abrasion, delamination and tribochemical (oxidative) modes of wear. This is an important issue for future research.展开更多
Total joint replacements(TJR) have been a huge success for orthopaedic surgery in the past century and are gaining increasing importance today due to the aging population. However, the short longevity of artificial jo...Total joint replacements(TJR) have been a huge success for orthopaedic surgery in the past century and are gaining increasing importance today due to the aging population. However, the short longevity of artificial joints is one of the major problems in bioimplant industry and needs to be rectified since an increasing number of young people, with more active lifestyles, must receive TJR. Wear mechanisms are discussed in this paper to describe the root causes of the failures and to give some general ideas to increase the lifespan of artificial joints. The suitable material combination is of great importance for the wear resistance of bioimplants, and bioceramics will exert a crucial effect in their future progress. Other materials, such as metal alloys and polymers, are also discussed in this paper. Surface finish is another factor affecting the tribological performance of bioimplants. In recent years, surface texture technology has fascinated many researchers, and a good design of texture pattern requires a comprehensive understanding of wear mechanisms, material properties, and dynamic fluid theory. This review also covers a summary of in vitro wear tests, including simulators, lubricant, and testing parameters.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51671063,51771060 and51871068)the Key Laboratory of Lightweight and high strength structural materials of Jiangxi Province(No.20171BCD40003)+4 种基金the Research Fund for the Doctoral Program of Higher Education(No.20132304110006)Heilongjiang Province Natural Science Foundation(No.ZD2017010)the Fundamental Research Funds for the Central Universities(No.HEUCFG201834)the Harbin City Application Technology Research and Development Project(Nos.2015RQXXJ001 and 2017RAQXJ032)the Science and Technology Innovation Project(No.009-031-001)
文摘Calcium phosphate(CaP) coatings were prepared on Mg–8Li–2Ca magnesium alloy by micro-arc oxidation(MAO) in an alkaline Na_3PO_4–Ca[C_3H_7O_6P] base solution at the different applied voltages. Scanning electron microscope and X-ray diffraction were employed to characterize the microstructure and phase composition of the coatings, respectively. The corrosion resistance of the coatings was assessed by potential dynamic polarization curves, electrochemical impedance spectroscopy and hydrogen evolution experiment in simulated body fluids solution. The friction and wear properties were evaluated by friction and wear testing machine. The results demonstrate that the coating surface is porous and mainly composed of MgO, Ca_5(PO_4)_3(OH) and CaH_2P_2O_5. With the increase in voltage, the corrosion resistance and wear resistance of the MAO coating are both enhanced. The corrosion current density of the MAO coating decreases about two orders of the magnitude compared to the substrate. Additionally, wear and corrosion mechanisms are discussed.
文摘Prior studies have noted that gas nitriding has a considerable effect for wear resistance. The aim of this paper is to study the influence of gas nitriding time (12, 24, 36 and 48 h) in the wear behaviour of 42CrMo4 steel. It has been assessed by micro hardness, pin-on-disc tribosystem, and SEM through the nitrided layer for each nitriding time. The study relates to the performance of the compound layer and the diffusion layer with respect to adhesive wear. The results were analyzed in terms of the weight lost during wear, for nitrided steel with and without the compound layer, and for untreated steel. It has been observed that wear rate varies as a function of the tests conditions due to the presence of different wear mechanisms. Thus, for short tests conditions wear rate depends on two mechanisms: plastic deformation and adhesive wear, whereas for large tests conditions the mechanisms controlling wear rate are abrasive and oxidative wear. Furthermore, this study contains an analysis of the wear mechanisms of a nitrided part, founded on scanning electron microscopy (SEM) observations of the wear traces at various stages of the evolution of wear. The SEM examination of worn surfaces revealed signatures for the adhesion, abrasion, delamination and tribochemical (oxidative) modes of wear. This is an important issue for future research.
基金support from the Science Foundation Ireland (SFI) (Grant No. 15/ RP/B3208)the National Natural Science Foundation of China (NSFC) (Grant No. 51320105009 & 61635008)
文摘Total joint replacements(TJR) have been a huge success for orthopaedic surgery in the past century and are gaining increasing importance today due to the aging population. However, the short longevity of artificial joints is one of the major problems in bioimplant industry and needs to be rectified since an increasing number of young people, with more active lifestyles, must receive TJR. Wear mechanisms are discussed in this paper to describe the root causes of the failures and to give some general ideas to increase the lifespan of artificial joints. The suitable material combination is of great importance for the wear resistance of bioimplants, and bioceramics will exert a crucial effect in their future progress. Other materials, such as metal alloys and polymers, are also discussed in this paper. Surface finish is another factor affecting the tribological performance of bioimplants. In recent years, surface texture technology has fascinated many researchers, and a good design of texture pattern requires a comprehensive understanding of wear mechanisms, material properties, and dynamic fluid theory. This review also covers a summary of in vitro wear tests, including simulators, lubricant, and testing parameters.
