TiN coating wear mechanisms in dry sliding contact against high speed steel

Dry sliding wear experiments at specific loads ranging between 20 and 250 N were conducted on a PVD TiN coating, are deposited onto an AISI M2 high speed steel substrate. The coating was worn against AISI Ma-type high speed steel pins using a pin-on-disc sliding configuration at a constant sliding speed of 0.7 m s(-1). Wear rates, coefficients of friction and temperatures of the pin were measured as a function of load. Three wear regimes were identified: (i) transfer and build up of oxidized pin debris on the coating at a 20-N load, (ii) increased polishing damage and brittle spallation failure of the TiN at loads in the 50-100 N range and (iii) a sharp transition to plastic deformation and microploughing of TiN at loads greater than 100 N, which coincided with the attainment of a critical steady-state pin temperature of approximately 160 degrees C. Softening of the TiN coating above this temperature leads to rapid wear and exposure of the substrate material. (C) 1998 Elsevier Science S.A. All rights reserved.