Medical forged CoCrMo alloy was treated by plasma nitriding process.The microstructures were characterized by 3Dprofiler,SEM and XRD.The tribological properties were investigated under lubrication of 25% bovine serum ...Medical forged CoCrMo alloy was treated by plasma nitriding process.The microstructures were characterized by 3Dprofiler,SEM and XRD.The tribological properties were investigated under lubrication of 25% bovine serum solution.Resultsshow that plasma nitriding is a promising process to produce thick,hard,and more wear resistant layers on the surface of CoCrMoalloy.All nitrided samples showed an important increase in the surface hardness due to the formation of harder CrN andCrN phases with compact nano-crystalline structures.The typical hardness values of HVincreased almost two times thanuntreated one.Under bovine serum lubrication,at low nitriding temperature the Coefficient of Friction (COF) of nitrided samplewas lower than that of untreated sample,but at high nitriding temperature the COF was almost the same as the untreated one.Compared with the untreated sample,the nitrided samples showed lower wear rates and higher wear resistance under differentnitriding temperatures.The adhesive wear is the main mechanism for untreated CoCrMo alloy and the wear mechanisms ofnitrided ones are the fatigue wear and slight adhesive wear.It is concluded that the improvement of wear resistance is ascribed tothe hard nitride formation of CrN and CrN phases at the nitrided surfaces.展开更多
基金the supports by Tribology Science Fund State Key Laboratory of Tribology (SKLT) at Tsinghua University(SKLTKF08A01)Fundamental Research Funds for the Central UniversitiesNational Natural Science Foundation of China (No.51005234)
文摘Medical forged CoCrMo alloy was treated by plasma nitriding process.The microstructures were characterized by 3Dprofiler,SEM and XRD.The tribological properties were investigated under lubrication of 25% bovine serum solution.Resultsshow that plasma nitriding is a promising process to produce thick,hard,and more wear resistant layers on the surface of CoCrMoalloy.All nitrided samples showed an important increase in the surface hardness due to the formation of harder CrN andCrN phases with compact nano-crystalline structures.The typical hardness values of HVincreased almost two times thanuntreated one.Under bovine serum lubrication,at low nitriding temperature the Coefficient of Friction (COF) of nitrided samplewas lower than that of untreated sample,but at high nitriding temperature the COF was almost the same as the untreated one.Compared with the untreated sample,the nitrided samples showed lower wear rates and higher wear resistance under differentnitriding temperatures.The adhesive wear is the main mechanism for untreated CoCrMo alloy and the wear mechanisms ofnitrided ones are the fatigue wear and slight adhesive wear.It is concluded that the improvement of wear resistance is ascribed tothe hard nitride formation of CrN and CrN phases at the nitrided surfaces.
