石墨的添加对NiCr-W-Ti自润滑复合材料高温摩擦学性能的影响

本文以Ni20Cr合金为基体添加稀有金属Ti、W粉末及石墨后,充分混合,采用机械合金化及热压烧结工艺制备了NiCr金属基复合材料,研究了石墨含量对NiCr金属基复合材料的组织结构和摩擦学性能的影响。在UMT-3高温摩擦试验机上进行了该复合材料同Al_2O_3陶瓷球的滑动摩擦磨损实验,利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)对复合材料及其摩擦测试后的形貌与结构进行观察分析,结果表明:当所添加石墨的质量分数为3wt.%时,复合材料具有相对较好的力学性能和摩擦学性能;当测试温度低于300℃时,摩擦表面未形成有效的摩擦膜,故磨损率较高;当温度高于500℃时,摩擦层中含有摩擦氧化物,摩擦表面被光滑氧化物所组成的润滑膜覆盖,对磨面具有很好的保护作用,因而磨损率降低。

Effects of Graphite Addition on Tribological Properties of NiCr-W-Ti Self-lubricating Composites at Elevated Temperatures

NiCr-W-Ti self-lubricating composites were fabricated by mechanical alloying and hot-pressing sintering.Ni20Cr alloy was taken as the matrix of the composites;meanwhile,W,Ti and graphite were added to it,and the influences of different amount of graphite on the microstructure and tribological properties of the composites at elevated temperatures were studied.The friction and wear properties of the composites sliding against AlO3 ceramic ball were evaluated on a UMT-3 high-temperature tribometer with a ball-on-disc configuration.The microstructure and worn surfaces of the composites before and after friction test were observed and analyzed by Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD).Results show that the NiCr-W-Ti composite with the addition of 3wt.％ graphite exhibits the best comprehensive properties of mechanics and tribology.When testing temperature below 300℃C,the effective tribo-film has not formed on the worn surfaces,which leads to high wear rate.When temperature higher than 500℃C,oxides can be found in the friction layer and the worn surfaces were covered by a lubricating film composed of smooth oxides,which effectively protect the worn surface and contribute to the wear rate decreasing.