Effect of Temperature on the Structure and Tribological Properties of Ti, TiN and Ti/TiN Coatings Deposited by Cathodic Arc PVD

Abstract

Monolayers of Ti and TiN coatings, as well as a Ti/TiN bilayer coating, were deposited on AISI M2 steel substrates using the PVD cathodic arc technique. The coatings had a thickness close to 5 μm and an average roughness between 98.6 and 110.1 μm due to the presence of microdroplets on the surface. The crystalline structure of the materials was analyzed using Grazing Incidence X-ray Diffraction (GIXRD) with an increase in temperature to study the dynamics of oxide formation. A phase composition study was conducted using the Rietveld refinement method. At the temperatures where critical growth of titanium oxides, both anatase and rutile, was observed, pin-on-disk tests were performed to study the tribological properties of the materials at high temperatures. It was determined that the oxidation temperature of Ti is around 450 °C, promoting the formation of a combination of anatase and rutile. However, the formation of rutile inhibits the formation of anatase, which is stable above 600 °C. In contrast, TiN showed an oxidation temperature of 550 °C, with an exclusive growth of the rutile phase. The Ti/TiN bilayer exhibited mixed behavior, with the initial growth of anatase promoted by Ti, followed by the formation of rutile. Oxidation and tribo-oxidation dominated the wear behavior of the surfaces, showing a transition from mechanisms related to abrasion at low and medium temperatures to a combination of abrasion and adhesion mechanisms at high temperatures (800 °C).