Mechanical and Corrosion Behavior of TiN Coatings Deposited on Nitrided AISI 420 Stainless Steel

TiN coatings are widely used in different applications for extending the lifetime of components due to their high hardness and good wear resistance. However, it is not convenient to deposit them on soft stainless steels. In this work, the wear and corrosion behavior of commercial TiN coatings deposited by Arc-PVD on nitrided and non-nitrided martensitic stainless steel was studied. Two different nitriding conditions were used, one at high temperature (HTN) and the other at low temperature (LTN). Nanohardness and microhardness were measured. The microstructure was characterized by OM, SEM, XRD and XPS. Pin on disk and erosion tests were carried out in order to evaluate their wear resistance. The corrosion behavior was analyzed in salt spray fog and electrochemical tests in NaCl solution and the adhesion was measured in Scratch and Rockwell C Indentation tests.The coating thickness was about 1.5 µm and its hardness of 34 GPa. The nitrided layers were 13 µm and 17 µm thick for LTN and HTN, the hardness was approximately 12 GPa for both nitrided samples. The nitrided layer improved TiN coating adhesion in the Scratch tests. The wear loss volume was similar for both duplex and only coated samples in pin on disk tests. Nevertheless, wear resistance was not good for the LTN or HTN + TiN coating system in the erosion tests. Regarding corrosion behavior, the coatings showed poor corrosion resistance and this could be related to the presence of porous defects, which allow the solution to reach and attack the substrate, thus producing coating detachment around the pits.