Experimental Study of the Influence of Deposition of Multilayer CrN/CrCN PVD Coating on Austenitic Steel on Resistance to Cavitation Erosion

The impact of deposition of multilayer CrN/CrCN coating on X6CrNiTi18-10 steel by means of the PVD (physical vapour deposition) method on resistance to cavitation erosion has been investigated. Cavitation tests were performed using a cavitation chamber with a barricade system at the inlet pressure p(1) = 600 kPa and the outlet pressure p(2) = 123 kPa. Deposition of CrN/CrCN coating allowed increasing duration of the incubation period and decreasing cumulative volume loss until 500 min of exposure. The erosion of the CrN/CrCN-X6CrNiTi18-10 system begins with the removal of microdroplets from the coating surface and surface undulation. The surface undulation increases with the exposure time leading to coating fracture in a brittle mode. Initiation sites of cracks were located inside the PVD coating. Measurements of surface roughness illustrate uneven degradation of the exposed surface and the location of slight and severe erosion zones. The Ra parameters obtained for the CrN/CrCN-X6CrNiTi18-10 system and X6CrNiTi18-10 steel after 180 min of erosion were comparable. An elongation of erosion test up to 600 min resulted in a higher increase in surface roughness of the CrN/CrCN coating-X6CrNiTi18-10 steel system in comparison to that of X6CrNiTi18-10 steel. With increasing exposition time, the rate of increase of the surface roughness decreased due to overlapping damage.