Hard Cr–Al–Si–B–(N) coatings deposited by reactive and non-reactive magnetron sputtering of CrAlSiB target

Highlights: • Cr–Al–Si–B–N coatings with amorphous structure. • Coatings demonstrate hardness in range of 18–30 GPa. • Coatings exhibit friction coefficient ∼0.4. • Coatings show a very high oxidation resistance up to 1300 °C. • Coatings withstand cyclic loads up to 1000 N for 10⁵ cycles without fracture. - Abstract: Relationships between chemical composition, mechanical and tribological properties, fracture resistance, thermal stability and oxidation resistance of the magnetron sputtered Cr–Al–Si–B–(N) coatings were determined using X-ray diffraction, scanning and transmission electron microscopy, glow discharge optical emission spectroscopy, nanoindentation, as well as pin-on-disk, scratch and impact tests. The coatings deposited in Ar showed high friction coefficient and wear rate of 0.8 and 46.0 × 10⁻⁶ mm³/N m during tribological tests compared with 0.4 and 2.0–2.1 × 10⁻⁶ mm³/N m of reactively deposited coatings. During impact tests, N-free coatings showed the smallest impact wear of 1.34 × 10⁵ μm³, but, in contrast to the N-containing coatings, demonstrated fracture even at a load of 800 N. It was explained by the fact that the N-free coating, having high hardness of 30 GPa, yet was very brittle. Structural changes and oxidation mechanism of the Cr–Al–Si–B–(N) coatings during annealing in air at temperatures up to 1300 °C were also studied in detail. It was revealed that the coating deposited in Ar showed the best oxidation resistance up to 1300 °C