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

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 x 10(-6) mm(3)/N m during tribological tests compared with 0.4 and 2.0-2.1 x 10(-6) mm(3)/N m of reactively deposited coatings. During impact tests, N-free coatings showed the smallest impact wear of 1.34 x 10(5) mu m(3), 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 degrees C were also studied in detail. It was revealed that the coating deposited in Ar showed the best oxidation resistance up to 1300 degrees C. (C) 2014 Elsevier B.V. All rights reserved.