Substrate effect on wear resistant transition metal nitride hard coatings: Microstructure and tribo-mechanical properties

Four types of different hard transition metal nitrides (TMN:ZrN, CrN, WN and TiN) coatings were deposited on Si (100) and 316LN stainless steel substrates using DC magnetron sputtering. A comprehensive study of microstructure and substrate dependent tribo-mechanical properties of TMN coatings was carried out. Higher hardness (H) and elastic modulus (E) were obtained for WN (H=40GPa and E=440GPa) and TiN (H=30GPa and E=399GPa) coatings. This is related to the formation of (100) and (111) preferred orientations in WN and TiN coatings, respectively. However, the less hardness and elastic modulus were obtained for ZrN and CrN coatings where (200) orientation is preferred. Remarkably, low friction coefficient (0.06–0.57) and higher wear resistance in the coatings deposited on steel substrates are directly associated with the higher resistance to plastic deformation (H3/E2) and the presence of intrinsic compressive stress. Three body wear modes enhanced the friction coefficient (0.15–0.62) and the wear rate in the coatings deposited on Si substrates. This is primarily associated with low fracture toughness of brittle single crystalline Si (100) substrates. Steel-on-steel contact was dominated in ZrN/steel sliding system. This occurs due to the severe adhesive wear mode of steel ball, whereas, the abrasive wear modes were attained for the CrN, WN and TiN coatings sliding against steel balls.