载荷对Ni3Al基自润滑复合涂层摩擦学行为的影响

Effect of Loads on Tribological Behaviors of Ni3Al Matrix Self-Lubricating Composite Coating

采用高能球磨结合喷雾造粒技术制备微米级球形Ni3Al基复合粉末,利用等离子喷涂方法制备涂层后考察其在不同载荷(5、10和20 N)下宽温域内(25~800℃)的摩擦学性能.用SEM、EDS和Raman分析磨痕、对偶销和磨屑的微观组织和物相组成,对比分析载荷对摩擦磨损机理的影响.结果表明:25~200℃时,载荷增加促进了润滑相的'析出效应',但载荷增至20 N时涂层发生塑性变形产生'封闭效应',使涂层摩擦系数和磨损率随载荷增加呈先减后增的趋势;400~600℃时,载荷增加导致的摩擦热加速了氧化进程,降低磨损表面剪切强度,从而使摩擦系数和磨损率持续降低;800℃时,磨损表面形成富含NiCr2O4、Ag2MoO4和NiO的连续、光滑釉质层,但在20 N时局部过高的接触应力使润滑膜破裂而发生剥落,导致摩擦学性能下降.

The micron spherical Ni3Al based composite powder has been fabricated by high-energy ball milling combined with spray granulation.Then it was deposited on an 1Cr18Ni9Ti stainless steel by plasma spraying to form a coating,then the influences of testing temperatures(25℃to 800℃)and loads(5 N,10 N and 20 N)on the tribological behaviors of this coating were evaluated.SEM,EDS and Raman techniques were adopted to study the lubrication and wear mechanisms of the coating tested at different loads,by analyzing the microstructure and phase constitutes of the wear debris,wear scar of the coating and the counterface pins.The results indicated that within temperature range 25~200℃,the increase of load from 5 N to 10 N accelerated the precipitation of the lubricant resulting from the synergism between the frictional heat and applied load,providing a friction and wear reduction.However,with further increasing the load to 20 N in this temperature range,the coating was deformed plastically,leading to blocking effect and thus increasing the friction and wear.At temperature from 400 to 600℃,the oxidation process was accelerated by the friction heat caused by the increased loads,thereby decreased the friction and wear.At 800℃,the worn surfaces tested at all the loads were covered by a continuous and smooth oxidized glaze layer,which was rich in NiCr2O4,Ag2MoO4 and NiO.The distinction was that when the load of 20 N was applied,the local high stress destroyed the integrity of the lubricating film,thereby decreased the tribological properties.