Design And Tribological Properties Of High-temperature Wear Resistant CoCrMo Matrix Composites Reinforced By Nano-SiC

With the development of technology,friction systems need to operate at higher speeds,loads and temperatures.Cobalt-based alloys have better high-temperature oxidation resistance and wear resistance than iron-based and nickel-based alloys.Nano-scale ceramic particles can effectively enhance the mechanical and tribological properties of alloys.Therefore,a cobalt-based composite materials reinforced by nano-ceramic particles can be obtained,which have excellent wear resistance under high temperature conditions.In this paper,powder metallurgy technology was used to prepare nano-SiC reinforced CoCrMo high temperature anti-wear composites.The effects of nano-SiC content,temperature,sliding speed,load and friction pair on the tribological properties of the composites were systematically studied,and the wear mechanisms of the composites were analyzed in detail.CoCrMo high temperature wear-resistant composites reinforced by nano-SiC ceramic particles were prepared by powder metallurgy technology,and the high-temperature tribological properties of composites were systematically studied.The results showed that the addition of nano-SiC led to the increase of the hardness and the decrease of the density of composites.The friction coefficient increased with the increase of nano-SiC content,but the friction coefficient decreased with the increase of temperature.The wear resistance of composites in high-temperature environment increased significantly with the increase of nano-SiC content.The wear mechanism of composites differed at different temperatures.As the temperature increased,the wear mechanism gradually changed from abrasive wear and plastic deformation to oxidative wear.CoCrMo-2.2 wt.%SiC had excellent high-temperature wear resistance from room temperature to 1000℃.The effects of sliding speed and load on the tribological properties of composites were investigated at room temperature and 600℃,respectively.At room temperature,the shear pressure and contact area of the composite material and the anti-friction material were larger at low speed,and the friction coefficient and wear rate were higher.At higher speeds,frictional heat also resulted in a reduction in sliding resistance and an improvement in the coefficient of friction and wear rate.However,when the speed was too high,the composite material will also soften,resulting in rapid wear.The high hardness at low loads had a favorable effect on the wear resistance of the material,but the hard abrasive particles can also cause insufficient friction reduction properties.The wear resistance of composites under high load conditions was not as good as under low load conditions.At 600℃,the oxide film on the surface of the composite material played a crucial role,and the high-speed and high-load conditions were more conducive to the formation of a high-strength oxide film.Si₃N₄,GCr15 and Al₂O₃ balls were selected to be matched with 2.2 wt.%nano-SiC reinforced CoCrMo matrix composite from room temperature to 1000℃,respectively.The effect of friction pairs on the high-temperature tribological properties of composite was explored.From room temperature to 600℃,the friction coefficients between the composite and the Si₃N₄ pair were the highest,and between 600 and 1000℃,the composite and the GCr15 pair had the highest friction coefficients.The composite with Si₃N₄ had the most excellent anti-wear performance in a wide temperature range.The wear mechanism of composite was similar to that of Si₃N₄ and Al₂O₃ ceramic balls,while the strength of GCr15steel balls decreased at high temperature,which aggravated the adhesive wear.