脲基脂润滑下钢材料的微动磨损

FRETTING WEAR OF STEEL UNDER UREA GREASE LUBRICATION

采用微动摩擦磨损试验机进行了脲基脂润滑下的GCr15钢/45号钢摩擦副微动试验。采用激光三维共焦显微镜、EDX元素分析等方法研究了脲基脂润滑减缓钢表面微动磨损的机理。结果表明,在微动完全滑移区,脲基脂润滑下的钢-钢摩擦系数和钢表面磨损远低于干摩擦下的值,且磨损主要发生在微动早期阶段。在微动试验初期,脲基脂因微动自清洗作用被排出钢-钢接触界面,高摩擦力致使接触界面形成磨坑和白层;此后接触界面周围的脂剪切分油,且分出的油浸入到磨坑中形成混合润滑状态,摩擦系数降低到较低的稳态值;NLGI00脲基脂比NLGI2脲基脂更好的抗微动磨损性能归因于其更大的分油量。同时,接触界面周围的脂和磨坑表面的油减少了空气与摩擦表面的接触,使接触界面氧化腐蚀得以降低;磨坑表面高硬度白层因稳态低摩擦力而持续存在,有益于减缓微动磨损。

The fretting behavior in the slip regime with urea grease lubrication for GCr15 steel/45 steel contact was studied and the mechanism of urea grease palliative effect was investigated by confocal laser scanning microscope, EDX, etc. Compared with dry friction, the friction coefficient of steel-steel and the surface wear of steel were decreased drastically under urea grease lubrication, and the wear occurred mainly at the early stage of fretting. Initially, owing to grease elimination from the contact zone by a self-cleaning action of fretting, the high friction force led to the formation of white layer and wear cavity on the steel surface, and then the oil, which was separated from the grease around the contact interface, penetrated into the wear cavity and the mixed lubrication was formed, while the coefficient of friction decreased to a low steady value. The more remarkable palliative effect of NLGI 00 grease than NLGI 2 grease attributed to the easier oil separation from the grease. In addition, the oxidation corrosion was reduced under oxygen deprived condition as a result of the presence of the grease around the contact interface and the separated oil at the contact interface. Furthermore, the high hardness white layer at the wear scar surface could not be destroyed on a large scale by the low stable friction force, which existed over the complete test duration and conduced to suppressing wear.