2019 Mondragon Rodriguez Arc PVD AlTiN Oxidation Tribology

The effect of temperature in high purity Ar (low oxygen partial pressure) on the oxidation and crystal phase evolution of c-Al0.66Ti0.33N arc-PVD coatings was investigated. High temperature tribology in Ar jet and adhesion behavior of the oxidized coating were addressed. The use of Ar protects the coating from the oxidation reactions and allowed to shed light into the details and paths of the nitride oxidation process. The c-Al0.66Ti0.33N nitrides were slightly oxidized in Ar even at high temperature (700 to 900 °C). The surface chemistry evaluation shows very thin Al- and Ti-based oxide layers formation after treatment at 700 °C in Ar. However, the onset formation of the rutile TiO2 oxide was detected only after treatment at 900 °C and was clearly found by low-angle XRD diffraction after 1000 °C. The XPS surface analysis of the oxidized samples at 800°C indicated the formation of extremely thin layers mainly composed of mixed oxides (α-Al2O3 γ-Al2O3 and rutile TiO2). The gradual changes in the chemical composition of the oxidized coatings observed at 900 °C clearly demonstrate the formation of gradient boundaries between Al-rich and Ti-rich oxy-nitride layers. After exposure at 1000 °C at least four oxides and oxi-nitrides layers and interlayers were found. Additionally, it is suspected that the transition oxide phases such as c-TiO, c-Al0.54Ti2.46O0.28N4.58, α-Al2TiO5 and TiOxNy might be precursors leading to the formation of thermodynamically stable rutile and alumina phases. Surface inspection after high temperature tribology in Ar jet showed formation of tensile cracks in the wear tracks and wear processes due to high size particle adhesion-abras.