XPS and SEM characterization of wheel/workpiece interface in grinding of superalloy

An investigation is reported of the physical and chemical reactions at the wheel/workpiece interface during grinding of a nickel-based superalloy K417. The temperature at the wheel/workpiece interface was measured using a workpiece–foil thermocouple and the forces were detected using a dynamometer. Scanning electron microscopy was used to examine deformations on ground workpiece surfaces and wear characteristic of abrasive grits. The chemical composition, of the ground surfaces, the depth chemical composition and the thickness of oxide layers were determined by XPS and its depth profile technique. A different burning colour was found on the ground workpiece surfaces when temperatures at the wheel/workpiece interface are >990 °C. Along with the emergence of a burning colour, adhesion occurs between the abrasive grits and the workpiece, causing plastically deformed coatings to appear and gradually spread on the ground workpiece surfaces. A physical model was proposed to account for the wear process of abrasive grits and the formation of plastically deformed coatings on the workpiece ground surfaces. Analysis by XPS reveals that chemical reactions take place on the workpiece surfaces due to the high temperatures generated in grinding, and transfer films composed of such oxides as Ni2O3, TiO2, Cr2O3 and A12O3 are formed on the workpiece surfaces. The colour generated on the ground workpiece surfaces depends on the thickness of the transfer films, which was found to be closely related to the interface temperature. Copyright © 2002 John Wiley & Sons, Ltd.