A Comparative Study Of White Layer Of GCr15 Steel And FALEX Steel On Fretting Wear Under Dry Condition And Grease Lubrication

White layer formed on the friction surface is an unease-etching layer compared to the matrix. And it has no significant characristics under optical microscope (OM). This study mainly focuses on the formation mechanism of white layer and its influence to the friction and wear under dry condition. Presently, little research of white layer under grease lubrication has been reported. This study is a comparative study of nucleation and early growth of white layer under different lubrication condition (dry condition and grease lubrication). This study is helpful to investigate the fretting wear behavior.The fretting wear tests with ball-on-flat contacts of had been carried out under dry condition and grease lubrication on a hydraulic fretting tester with high precision. GCr15 steel and Falex steel were selected as the plate sample, and GCr15 ball with diameter of 12.6mm were selected as the country-body. Optical microscope (OM), laser Confocal scanning microscopy (LCSM), scanning electron microscopy (SEM) have been performed to indicated the formation progress of white layer and its influence to the tribology behavior under dry condition and grease lubrication. The main results and conclusion are as follows:The white layer was formed obviously on the worn surface of GCr15 steel during both lubrication conditions. The white layer generated after a few cycles under dry condition while it was delayed under lubrication.The coefficient of friction of GCr15 steel under grease lubrication was lower than that in dry condition and the appearing time of highest coefficient of friction under grease lubrication was lagged. The wear and coefficient of friction decreased owing to both effects of white layer and lubrication obviously.Compare to GCr15 steel, Falex steel had a similar result under dry condition and grease lubrication except a more lagged nucleation of white layer and a light wear. Especially to Falex steel, grease could decrease the coefficient of friction and reduce the abrasion obviously. The tangential stress strongly affected the formation of white layer and was also the main reason of the failure. The white layer formed easily at a high tangential stress condition. The formation and failure of white layer was a homeostasis process. The tangential stress was still the major factor for controlling the growth of white layer under grease lubrication.