Structure and Wear Resistance of Composite TiC-NiMo Coating Produced by L-DED on Ti-6Al-4V Substrate

Abstract

Fabrication of W- and Co-free wear-resistant cermets is a vital task in modern machinery due to the toxicity of Co-based products and poor availability of Co and W containing raw materials. In this paper, a TiC-NiMo coating produced by laser-directed energy deposition (L-DED) on a Ti-6Al-4V substrate was demonstrated. Mechanical alloying of TiC, Ni and Mo powders followed by spray-drying was proposed to fabricate a feedstock spherical composite powder suitable for an L-DED machine. It was shown that this method is more applicable in the case of a TiC-containing composition than gas atomization and plasma spheroidization methods. The size of the resulting particles was in the range of 10–100 μm while the size of the 70 vol.% was in the range of 45–75 μm. L-DED provided a good adhesion of the coating, though the presence of pores and transverse cracks was also observed. The coating’s hardness was up to 1500 HV, which is not inferior to the hardness of known TiC-based cermets and is promising for obtaining a good wear resistance of the coating. It was shown that it depended on the thickness due to the mixing zone influence. The coating structure contained TiC- and Mo-based precipitates and a Ni-based binder. The weight loss of the coating samples after an abrasive wear test with 4000 revolutions of a testing wheel was 0.0464 g and that can be considered insignificant. The wear did not lead to the appearance of new defects and cleavage of the coating. Further optimization of the component ratio and L-DED parameters could help to improve the performance of the coating and make this technology rather promising to improve the wear resistance of machinery parts working in high-wear environments.