Depletion of Monolayer Liquid Lubricant Films Induced by Laser Heating in Thermally Assisted Magnetic Recording

The white layer (WL) generally refers to an untempered martensite layer generated by severe sliding conditions, such as cutting, drilling, grinding, milling, and electron-discharge machining. Numerous tribologists have investigated the effect of the WL on wear behavior, but this phenomenon is not yet clearly understood because no attempt has been made to correlate the wear mechanism of the WL with its wear behavior. It is necessary to investigate the effects of the WL on wear comprehensively. Therefore, elasto-plastic properties, wear resistance, and wear mechanism of WL were studied with nanoindentation and wear tests. The results of this study show that the elastic moduli, yield strength, and hardness of the WL increased by approximately 170, 390, and 180%, respectively. Thus, it was found that the WL had distinct properties with respect to the substrate of AISI 52100 steel. It is possible that the increased surface hardness is an advantage in terms of wear resistance. However, the advantage diminishes, and the WL is subject to wear when delamination dominates the wear mechanism.