Experimental research material characteristics effect on white layers formation in grinding of hardened steel

Many studies have been performed on the formation of white layer. However, little study has been done to investigate the effects of material characteristics on the formation and thickness of white layer. In this study, grinding experiments are carried out by using four different steels (hardened and annealed) as workpiece material. The specimens are analyzed using a microhardness tester and an optical microscope. The experiments indicate the depth of white layer increases with the carbon content of workpiece materials. There is a critical carbon content (about 0.77 %) associated with thick white layer. Microhardness of white layer increases with the carbon content in hardened steel. A higher hardness is observed in the hardened steel than that in annealed steel, while there is not a softer transition zone in the annealed steel. White layer varies with the different combinations of grinding parameters. White layer thickness increases with the grinding depth and wheel speed. Based on experimental data, nonlinear regression statistical models are proposed to predict white layer thickness during grinding.