Study on Characteristics of ADI Coated DLC/ TiN /TiAlN Coatings by Cathodic Arc Evaporation

Abstract

In this study, austempered ductile iron (ADI) substrate containing acicular ferrite and high-carbon austenite in the microstructure is made by austempering treatment at 360. Cathodic arc evaporation (CAE) coating technique was used to coat DLC, TiN and TiAlN films on ADI for surface modification. The results showed that the three coatings could be successfully coated onto ADI through CAE process without altering the unique microstructure of ADI. The structures of the coatings were identified by XRD, Raman and TEM, respectively. After HRC indentation testing, it was found that nodular graphite was the initial site of cracking for the coatings and then peeled. Surface roughness of all coated specimens was increased because the droplets generated on the substrate surface during the CAE process. Coated ADI had better wearability performance than uncoated ADI due to higher surface hardness. Coated specimens exhibited higher corrosion resistance than uncoated ones when they were immersed in separate solutions of both 3.5 wt. % NaCl and 10 vol. % HCl. In particular, TiAlN had the best corrosion resistance among the coated specimens.