Erosion and corrosion behaviors of ADI deposited TiN/TiAIN coatings by cathodic arc evaporation

Austempered ductile iron (ADI) is a heat-treated ductile iron with acicular ferrite and high-carbon austenite as the matrix of the microstructure. The purpose of this research is to investigate the influence of different hard coatings (PVD-TiN and PVD-TiAIN) on the erosion and corrosion properties of ADI. Also, the coating structure and property were analyzed by using XRD, Rockwell C tester and SEM. The results showed that TiN and TiAIN films identified by XRD could be well deposited on the ADI substrate by the PVD method of cathodic arc evaporation (CAE). Adhesion between coating-layer and ADI substrate was better than that between coating-layer and DI substrate. It was found that the initial source of coated layer peeled for the both substrates occurred at the graphitic sites. The depositing rate of TiAIN was rapider than that of TiN, but it also resulted in the thicker coating thickness and rougher surface for the specimen coated with TiAIN film. After slurry erosion test, the result revealed that erosion resistance of coated specimens was better than that of uncoated specimen. In 3.5 mass% NaCl aqueous for polarization curve test, corrosion current of TiAIN Him was smaller than that of TiN film. In 10 vol% HCl solution for immersion test, both TiN and TiAIN coatings could raise the corrosion resistance for ADI material.