Titanium Nitride Coatings on Tool Steels

This book describes the methodology and characteristics of hard coatings on tool steel, viz. TiN coated on high-speed steel and D2 tool steel by cathodic arc physical vapour deposition (CAPVD) technique. The main drawback of CAPVD, however, is the formation of macrodroplets (MD's) during deposition, resulting in films with rougher morphology. The presence of MD's in the coating is a serious problem during practical tooling applications. Standard characterization techniques and equipment were used to analyze and quantify the deposited coatings. The MD's contamination and growth mechanisms were investigated as a function of various process parameters. The results showed that the nitrogen flow rate was the most important factor in controlling the size and number of the MD's. 3D AFM images and electron microscopy indicated that the MD's were generated during the etching stage and protruded through the TiN film during deposition process. The TiN coating thickness decreased from 7.1 to 5.7 m as the bias voltage is increased from zero to -150 V. The effect of ion etching was also investigated. The coatings deposited on HSS exhibited better adhesion compared to those on D2 tool steel.