钇(Y)元素强化的CoCrNiFe基高温自润滑复合涂层的摩擦学性能

Tribological Properties of CoCrNiFe Matrix High-temperature Composite Coatings Reinforced by Yttrium Element

采用热压烧结技术在GH4169镍合金表面制备Y(0.5%、1.0%、2.0%(质量分数))强化的CoCrNiFe基高温自润滑复合涂层,系统研究了Y对CoCrNiFe基涂层微观组织和高温摩擦学性能的影响,优化Y含量。在室温到1000℃内,采用球-盘配置的摩擦试验机与Si_(3)N_(4)球配副测试涂层的高温摩擦学性能。使用X射线衍射仪(XRD)、扫描电镜(SEM)分析涂层的微结构及高温摩擦磨损机理。结果表明:涂层由γ-Co(fcc)、ε-Co(hcp)、FeNi_(3)、Ni_(2.9)Cr_(0.7)Fe_(0.36)和Y_(2)O_(3)相组成。在烧结过程中,Y与金属颗粒表面吸附的氧或其他氧化物杂质反应净化了晶界,所生成的Y_(2)O_(3)明显改善了涂层的硬度和致密度。涂层的显微硬度和致密度随着Y含量的增加而升高。涂层试样的摩擦系数随温度的升高先减小后增大,在800℃时达到最小值。其磨损率变化趋势则相反,在20~600℃内,涂层的磨损率较基底下降23.64%~95.90%,1000℃时磨损率约为3×10^(-5)mm_(3)/(N·m)。这归因于涂层的高硬度以及Y_(2)O_(3)强化的氧化物润滑层的润滑作用。含1.0%Y的涂层表现出最佳的高温摩擦学性能。涂层在低温下的磨损机理为磨粒磨损和轻微的塑性变形,高温时的磨损机理主要为氧化磨损。

The CoCrNiFe matrix composite coatings with Y(0.5wt%,1.0wt%,2.0wt%)were prepared on the surface of GH4169 nickel alloy by powder metallurgy technology.The effects of Y on the microstructure and tribological properties of the coatings were systematically investigated,and the Y content was optimized.The high-temperature tribological behaviors were tested by using ball-on-disc tribo-tester from room tempe-rature to 1000℃sliding against Si_(3)N_(4) ball.The XRD and SEM technologies were used to analyze the microstructure and high-temperature wear mechanism of the coatings.The main phases of the coatings consisted ofγ-Co(fcc),ε-Co(hcp),FeNi_(3),Ni_(2.9)Cr_(0.7)Fe_(0.36)and Y_(2)O_(3).The Y element reacted with the adsorbed oxygen and other oxide impurities on the surface of metal particles during the sintering,so the grain boundaries were purified.The Y_(2)O_(3)could effectively enhance the hardness and compactness of the coatings,and the hardness and compactness of the coatings were improved with the increase of Y element content.The friction coefficients of the coatings first decreased and then increased with the increase of temperature,and the coatings showed the minimum friction coefficients at 800℃.However,the wear rates had an opposite trend.From 20℃to 600℃.The wear rates of the coatings were 23.64%—95.90%lower than that of the substrate,and the wear rate was about 3×10^(-5)mm^(3)/(N·m)at 1000℃.It was ascribed to the high hardness and the lubricating effect of oxide film reinforced by Y_(2)O_(3).Generally,the composite coating with 1.0wt%Y had the best tribological properties at high temperature.The wear mechanism of the coatings was abrasive wear and slight plastic deformation at low temperature while oxidation wear was the wear mechanism at high temperature.