Cavitation erosion resistance of nanocrystalline TiN coating deposited on stainless steel

Nanocrystalline TiN coating was deposited on stainless steel X6CrNiTi18-10 by means of the cathodic arc method. The evaluation of nanocrystalline TiN coating resistance to cavitation erosion was based on the investigation performed in a cavitation tunnel with a slot cavitator and tap water as a medium. The investigations were performed at variable cavitation intensity. The estimated cavitation resistance parameters of coatings were the incubation period of damage and the instantaneous erosion rate after exposure of specified duration. It has been confirmed that the nanocrystalline TiN coating deposition on X6CrNiTi18-10 steel causes prolongation of the incubation period in comparison with the uncoated steel, the instantaneous erosion rates are close to each other, but after incubation period higher erosion rate was on the TiN coated specimen. The character of the TiN coating and uncovered substrate damage in multiple locations indicated that the hard coating micro-particles torn off during the cavitation bubbles implosion hit against the coating and the revealed areas of substrate. As a result, the TiN coating and especially the substrate of relatively low hardness beside cavitation erosion are subject to solid particle erosion with the hard torn off micro-particles of coating. The investigations and the analysis indicated that the main factors responsible for an elongated incubation period of the steel substrate/hard coating systems are the gained high hardness of substrate and high level of coating adhesion.