Phase composition, structure, and mechanical properties of arc PVD Mo–Si–Al and Mo–Si–Al–N coatings

Abstract

Using an arc physical vapor deposition process, we have produced nanostructured Mo–Si–Al coatings with a uniform distribution of equiaxed grains 8–12 nm in size and Mo–Si–Al–N coatings with a multilayer structure and a modulation period from 22 to 25 nm. The former coatings consist of MoSi₂ and Mo and the latter consist of Mo2N and amorphous Si₃N₄ and AlN. The hardness of the Mo–Si–Al–N and Mo–Si–Al coatings is 41 and 18 GPa, respectively; they are similar in resistance to elastic deformation; and the Mo–Si–Al–N coating has a considerably higher resistance to plastic deformation. The coatings have roughly identical coefficients of friction (~0.67–0.69 at 20°C and ~0.52–0.56 at 550°C), but the wear resistance of the Mo–Si–Al–N coating is higher by three and two orders of magnitude at 20 and 550°C, respectively. The coatings of the two systems exhibit good adhesion to the substrate and cohesive fracture. Partial wear of the Mo–Si–Al and Mo–Si–Al–N coatings in the course of scratch testing occurs at indentation loads of 80 and 63 N, respectively.