Sputtered nitride and boride coatings of titanium and zirconium: influence of ion bombardment on structure, mechanical properties and corrosion protection

Nitride and boride coatings of titanium and zirconium are widely used in increasing the performance of various cutting tools. Besides, increasing interest has been paid on their corrosion protective and functional properties. A restriction of their deposition at relatively low process temperature (i.e. on machine components) is the formation of porous film morphology, accompanied by inferior properties. The aim of this work is to investigate the effect of moderately energetic intense ion bombardment on the structure, mechanical and corrosion properties of nitride and diboride coatings of titanium and zirconium, deposited by unbalanced d.c. magnetron sputtering, as well as to extract some technical data for those coatings. Deposition was carried out non-reactively at a process temperature of 300 degree C and an inert gas pressure of 0.8 Pa. The coatings with a thickness of 3-4 μm were deposited on plain carbon steel and molybdenum substrates by bombarding with argon ions of varying energy and dose. The coatings were characterized with respect to their chemical composition, film morphology, micro structure, hardness, adhesion, tribological and corrosion properties with the help of wave-length electron probe microanalysis (EPMA), scanning electron microscopy (SEM), X-ray diffractometry, Vickers microhardness and depth sensing indentation, scratch test, ball-on-disk test and potentiodynamic measurements, respectively. The moderately energetic intense ion bombardment has been found to be an efficient tool for the tailoring of the concerned coatings. Morphological and structural chances have been discussed. Consecutive improvements and application related properties have been inferred. The coatings have been compared as well. (author)