Arc evaporated W-alloyed Ti-Al-N coatings for improved thermal stability, mechanical, and tribological properties

Therefore, we studied in detail the impact of tungsten (W)-in combination with the substrate bias potential (Ubias)-on the thermo-mechanical properties and wear performance of arc evaporated Ti1 - x − yAlxWyN thin films. With increasing W content, the quality of our coatings significantly increases due to pronounced reduction of growth defects (quantity of macro particles). All coatings studied crystallize in a supersaturated, single-phased face-centered cubic Ti1 − x − yAlxWyN structure and their hardness (H) increases whereas the indentation modulus (E) decreases with increasing W content. This results in increased H3/E2 values, with a maximum of 0.19 GPa for Ti0.50Al0.41W0.09N prepared with Ubias = −120 V (H ≈ 35 GPa, E ≈ 483 GPa). All W-alloyed coatings exhibit wear rates below 4 ∙ 10− 5 mm3/Nm during our dry sliding pin-on-disk tests against alumina balls at room temperature, with a tendency for reduced values if more droplets are present. The highest thermal stability, with respect to the decomposition of the supersaturated Ti1 - x − yAlxWyN phase towards the stable constituents (at high temperature) TiN, AlN, and W, is obtained for Ti0.53Al0.42W0.05N prepared with Ubias = −80 V. Here, the formation of the wurtzite-structured AlN can be delayed to 1000 °C after 60 min lasting isothermal annealings in vacuum.