Tribological study at high temperature of the c-TiAlON oxynitride coating deposited by cathodic arc on H13 tool steel

Coatings were deposited on AISI-H13 steel by cathodic arc Physical Vapor deposition (arc-PVD). Grazing Incidence X-Ray diffraction (GI-XRD) showed that Oxygen atoms (O) replace Nitrogen atoms (N) in the cubic-Titanium Aluminum Nitride (c-TiAlN) lattice. The coating had ∼5.9 µm thickness, ∼6.3 at% O content and average roughness of Ra= 73.9 nm. High-temperature GI-XRD showed improved oxidation resistance up to 850 °C, at 900 °C the constituent oxides appeared. A columnar microstructure resulted in 21.72 GPa hardness and 418.31 GPa elastic-moduli. Adhesion tests showed critical loads > 19 N, with chipping and conformal-cracking. The pin-on-disk tests at room temperature (RT) showed coefficients of friction (COF) of 0.65 and 0.83 for the steel and the oxynitride, respectively. At 900 °C the COF decreased due to a tribolayer formation. Cyclic tribo-oxidation cause this tribolayer to wear and partially expose the substrate, showing wear mechanisms due to combined processes of the coating and the steel.