Application of Micro Slurry-Jet Erosion (MSE) for the Evaluation of Surface Properties of PVD TiN / TiCN Two-Layer Coatings

Abstract

In this study, the potential of a Micro Slurry-jet Erosion (MSE) test to swiftly evaluate the intrinsic surface strength properties of thin multi-layer coatings is demonstrated. A slurry containing 1.2 μm alumina particles was impacted at high velocity perpendicular to PVD TiN/TiCN (TiCN on top of TiN) and TiN coatings deposited on high-speed steel by a hollow cathode discharge (HCD) or an cathodic arc (CA) method. In addition, nano-indentation and XRD, GDOES analyses were done for the original surfaces. By measuring the variation of erosion depth against test time, the MSE test made it possible to evaluate the individual erosion properties of TiCN and TiN layers independent of the substrate. Although the hardness of TiCN layers, coated by HCD or CA, was measured with nano-indentation and found to be approximately 20% higher than for TiN, the erosion rates of TiCN layers were found to be between 32% and 38% of the erosion rate of TiN. For the HCD coating, the erosion proceeded uniformly and produced a mostly smooth surface. On the other hand, for the CA coating, a pitted surface was observed. The existence of the hollows blemishes which caused by macroparticles i. e. droplets in the coating may affect the difference in the erosion rates between HCD and CA coatings. Consequently, the MSE test may be useful to evaluate the difference of the morphology of coatings as well as the surface strength which are related with the fabrication process.