REACTIVE UNBALANCED MAGNETRON SPUTTERING OF THE NITRIDES OF TI, ZR, HF, CR, MO, TI-AL, TI-ZR AND TI-AL-V

Reactive unbalanced magnetron sputtering was used to deposit eight different nitride coatings on hardened 440C stainless steel rolling contact fatigue (RCF) test specimens. The target materials used in this study were Ti, Zr, Hf, Cr, Mo, Ti0.5Al0.5, Ti0.5Zr0.5 and Ti-Al-V (the aircraft alloy Ti-6 wt.%Al-4 wt.%V). All the coatings were characterized using X-ray diffraction, microhardness and scratch adhesion tests. Ti, Zr and Hf form the simple binary nitrides of TiN, ZrN and HfN, respectively, with an fc.c. structure and a range in stoichiometry. Cr and Mo form a range of nitrides, starting with a solid solution of nitrogen in each of them, a Cr2N or Mo2N phase, and a CrN or MoN phase. The MoN phase was not conclusively formed in this work. Mo2N forms in two different phases, i.e. beta and gamma phases, depending on the nitrogen partial pressure. The Ti-alloyed nitrides all form an fc.c. structure. The coatings selected for the RCF tests ranged in hardness from a low of 1900 kg mm-2 for Ti0.5Al0.5N and CrN to a high of 2800 kg mm-2 for Ti0.5Zr0.5N. The deposition conditions for forming these nitrides are given in this paper. Also, the similarities and differences, both in the deposition conditions and in the resulting properties, are reviewed.