Structure formation of adaptive arc-PVD Ti-Al-Mo-N and Ti-Al-Mo-Ni-N coatings and their wear-resistance under various friction conditions

摘要

The regularities of the formation of arc-PVD coatings Ti-Al-Mo-N and Ti-Al-Mo-Ni-N and their properties under various friction and loading conditions were investigated in this work. Coatings of about 4 mu m in thickness were obtained by arc-PVD using cathodes of pure Mo, Ti-5% Al, and Ti-50% Ni in a nitrogen atmosphere. Obtained coatings had layered structure with alternating layers based on (Ti,Al)N and MoN. The grain size was about 40-50 and 10-12 nm for Ti-Al-Mo-N and Ti-Al-Mo-Ni-N coatings, respectively. Under dry friction conditions, TiAl-Mo-N and Ti-Al-Mo-Ni-N coatings exhibited similar friction coefficients at room temperature (0.63 and 0.65, respectively) and at 500 degrees C (0.42 and 0.45, respectively) with insignificant wear. However, the wear mechanism of the coating material under friction conditions at 500 degrees C was different. At higher temperatures, the wear of the Ti-Al-Mo-Ni-N coating was higher than that of Ti-Al-Mo-N. This is due to the fact that along with the formation of MoO3 during friction, TiNiO3 oxide was formed. Simulation of the abrasive wear has shown that coatings' abrasion occurs cohesively by the mechanism of plastic deformation without significant cracking till the load of 40 and 50 N for Ti-Al-Mo-N and Ti-Al-Mo-Ni-N, respectively. This is due to the high fracture toughness of the coatings (relative work of plastic deformation of similar to 60% and 70% for Ti-Al-Mo-N and Ti-Al-Mo-Ni-N, respectively) along with their high hardness (37 and 45 GPa). Testing of coatings in a multi-cycle impact loading indicated that investigated coatings are highly resistant due to the combination of high hardness with plasticity and increased bond strength with the substrate.