Surface treatment of tool steels against galling failure

In the present study two highly alloyed steel grades, intended for cold working applications, were subjected to plane-contact, nonlubricating sliding friction testing in order to estimate the working regions (applied pressure and sliding velocity) that are governed by mild, moderate and severe wear mechanisms, before and after nitrocarburizing. For this purpose, both tool steel grades were initially pre-subjected to the proper heat treatments, in order to achieve a final bulk hardness of 40, 50 and 60 HRC whereas, after heat treatment, half of the material specimens were further subjected to nitrocarburizing surface treatment. The comparative experimental study of heat-treated and heat-/ surface-treated grades within a wide range of applied pressure and sliding velocity values, in combination to the development of a relevant Artificial Neural Network, allowed to determine the areas of recommended operation of such tribosystems. In all cases, the positive influence of the post-hardening surface treatment was proved; further work is in progress to generalize these preliminary results and establish the relevant wear maps correlating the wear lifetime, the hardening levels and the surface treatment to the operational plane sliding conditions.