渗氮GCr15钢在含氮硼酸酯添加剂润滑油作用下的摩擦学性能

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An approach combining the plasma nitriding with lubrication additive is proposed to improve the durability of the antifriction bearing.The nitrided layer on GCr15 steel is prepared in a plasma nitriding furnace.Its surface morphologies,phase structure,and hardness are analyzed by means of scanning electron microscope（SEM）,X-ray diffractometer（XRD） and microhardness tester.Its friction and wear behaviors are examined on a four-ball friction and wear tester under lubrication with borate containing nitrogen additive,compared with that of plain GCr15 steel.The composition and chemical binding state of tribofilm formed on the wear steel surface is analyzed by X-ray photoelectron spectroscope（XPS）.The results show that an unexpected excellent synergistic effect occur between the nitrided surface and additive,the nitrided steel exhibits lower friction coefficient and better anti-wear properties compared with untreated steel,especially when 1.25% additive is used,the friction coefficient and wear scar diameter reduce by 34% and 45% separately.The main mechanism of this effect is attributed to that the borate containing nitrogen additive can produce a tribofilm containing higher content of BN on the nitrided surface,which is not found on the plain steel surface.针对提高滚动轴承使用寿命的问题,提出离子渗氮处理与添加剂结合的解决办法。用等离子渗氮炉在GCr15轴承钢表面制备了渗氮层,并用扫描电子显微镜（Scanningelectronmicroscope,SEM）、X射线衍射仪（X-raydiffractometer,XRD）和显微硬度计观测了渗层的形貌、相结构和硬度变化。利用四球摩擦磨损试验机对比考察渗氮钢和未渗氮钢在含氮硼酸酯润滑条件下的摩擦学性能,并用X射线光电子能谱仪（X-rayphotoelectronspectroscope,XPS）分析摩擦反应膜的成分与化学结合态。结果表明,渗氮层与润滑油添加剂之间发生了意想不到的良好交互作用,渗氮钢在质量分数为1.25氮硼酸酯的润滑条件下表现出最低的摩擦因数和磨斑直径,比未渗氮钢分别降低了34和45;分析证明,渗氮层的摩擦表面生成了高BN质量分数的摩擦反应膜是获得优异摩擦学性能的主要原因,而在未渗氮钢摩擦表面未检测到BN。