Investigations on friction and wear mechanisms of the PVD-TiAlN coated carbide in dry sliding against steels and cast iron

The tribological behaviour of the monolayer PVD-titanium aluminium nitride (TiAlN) coated carbide inserts in unidirectional dry sliding against steel and cast iron counterparts was investigated using the pin-on-disc standard test with varying sliding speeds and normal loads. Three different materials of various machinability rates were used as the counterparts, namely the normalised medium carbon steel C45 equivalent to AISI 1045, austenitic stainless steel 1H18N9T equivalent to AISI 304 and gray cast iron EN-GJL-300 with flake-shaped graphite. A pin-on-disc device with round tool inserts was used to conduct friction and wear tests in which both the friction coefficient and the linear wear of the tribo-pairs were continuously recorded versus sliding distance. For the quantitative comparison of the wear resistance of the tribo-pairs tested the volumetric wear rate was selected. Light microscopy (LM), scanning electron microscopy (SEM) and X-ray microanalyses by EDAX were applied for observations of wear scars and wear products, and the identification of the predominant wear mechanisms which occurred. Some specific frictional behaviours and relevant wear mechanisms observed for both steels and cast iron sliding over thin TiAlN layer are highlighted and quantified. Moreover, the contact conditions, under which the TiAlN film can protect the carbide substrate are specified. It is concluded that for sliding materials with dominating severe adhesive wear, as for example for the couple TiAlN/stainless steel, the protective function of the TiAlN coating is not sufficient.