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