Tribological Behavour of Heat Treated Cold Work Steels

ABSTRACTThe present experimental work investigates the friction and wear behavior of commercial cold work tool steels. The aim of the work is to get optimal combination of hardness, friction coefficient and wear by various heat treatment processes and tempering temperatures. Quenching, tempering, martempering and finally austempring treatments were applied to the tested steels. The hardness (HRC) of the steels after heat treatment was determined to evaluate the surface resistance to wear. Scratch test was carried out using a diamond stylus of specified geometry along a straight line path under dry sliding condition. Friction coefficient was calculated to give specific information about surface tribological property. Wear scar width as a measure of wear was measured using optical microscope. It was found that as received specimens showed the lowest hardness, while the highest value of hardness was observed for specimens quenched in oil and normalized in air. The hardness decreased with increasing tempering temperature. The highest values of friction coefficient were displayed by oil quenching followed by normalizing processes. As received specimens showed relatively higher values of friction coefficient. Oil quenched specimens displayed minimum friction coefficient. Significant reduction in friction coefficient and wear was observed for test specimens cooled by compressed air and tempered. Maximum wear was displayed by as received specimens, while minimum wear was presented by specimens quenched in oil and normalized in air. Oil quenched specimens displayed relatively low values of wear. Wear decreased for test specimens cooled by compressed air and tempered.