Micro-abrasion wear testing of PVD TiN coatings on untreated and plasma nitrided AISI H13 steel

An abrasive wear test, based on the ball-crater technique, has been used to evaluate the wear resistance of PVD TiN coatings, on untreated and plasma nitrided AISI H13 steels. Knoop microhardness measurements and scratch tests were carried out to characterise the coating systems under investigation. The TiN on plasma nitrided “duplex” coatings showed better micro-abrasive wear resistance than the single-layered TiN coatings and uncoated AISI H13 substrate. The best performance of the duplex-treated sample can be attributed to the presence of a nitrided subsurface in comparison with that of the single-layered TiN coating. The presence of a hard nitrided layer seemed to diminish the scratching action of the SiC abrasive particles. The wear patterns also indicated a transition between wear mechanisms, depending on the surface (coating) and subsurface hardness. A grooving wear mechanism was observed for a single-layered TiN coating (deposited on a hardened AISI H13 substrate) whilst a mixed mechanism involving grooving and rolling wear was found to occur in a duplex TiN coating (plasma nitrided AISI H13 substrate).