Micro Damages and Mechanism of a Powder Layer under Particulate Lubrication

Loose graphite powder is used to lubricate the plane contact tribopairs, and the formation and damage behavior of the powder layer is analyzed. The typical life cycle of a powder layer includes the full powder layer, partial detachment, serious detachment, and complete destruction, which can be concluded from the powder layer images and the analysis of the carbon and copper content remaining on the surface by scanning electron microscopy and energy dispersive X-ray spectroscopy. Layer blistering, partial detachment, delamination, and scuffing, which represent the different forms of damage and deterioration grades, are observed using an optical microscope. Layer blistering, partial detachment, and delamination are the damage forms that occur at earlier stages. Scuffing, which indicates direct contact and rubbing between the steel surface of the upper sample and the copper surface of the bottom sample, is a serious form of damage and is observed before the full destruction of the powder layer.