Cathodic arc deposited thin film coatings based on TiAl intermetallics

Intermetallics based on TiAl have been extensively investigated for a variety of structural applications due to their unique properties such as low density and high strength. Strategic functional applications necessitated the use of TiAl intermetallic cathodes to obtain thin film coatings of (Ti,Al)N to protect the tool materials from wear and abrasion. (Ti,Al)N coatings are essential for machining of hard metals and super alloys due to their high hardness and good thermal stability. In addition, they are also used for dry machining applications. In this paper, we summarize the influence of composition and processing variables of TiAl cathodes on the cathodic arc deposition of (Ti,Al)N coatings. The hardness and adhesion properties of the coatings deposited on M2 steel were evaluated and correlated with the composition (Al/Ti ratio) of the coating. In addition, gradient (Ti,Al)N coatings were developed by varying bias voltage during the deposition of coatings. Our results indicate that the gradient coatings of (Ti,Al)N provide better adhesion as compared to a single layer (Ti,Al)N coating containing a fixed amount of Al and Ti.