Adhesion and structure of TiN arc coatings

Abstract

TiN coatings were deposited with the arc technique at different substrate temperatures (200–450°C) and different bias voltages (0–400 V). The adhesion of the coatings on HSS substrates was then determined using the scratch test. The structures were recorded by scanning electron micrographs of the fracture surfaces. This showed that, in the case of arc coatings, the critical load increases more substantially with increasing temperature than with the increasing bias voltage, except from 0 to 100 V. Coatings deposited at a substrate temperature of 200°C exhibit a relatively high average critical load of 60 N and an unusually dense structure. Critical load values of more than 90 N can be obtained at higher substrate temperatures of around 450°C. As the result of a bias voltage of only 100 V, the adhesion increases by more than a factor of 2 compared with the unbiased condition, and simultaneously the droplet and exhibit a nearly equiaxed structure. Furthermore, partial epitaxial growth can be detected at the interface. When compared with triode-ion-plated TiN coatings from parallel production, arc coatings exhibit a better adhesion (higher critical loads).