Laser clad TiC reinforced NiCrBSi composite coatings on Ti-6Al-4V alloy using a CW CO2 laser

TiC-NiCrBSi composite coatings were fabricated on Ti-6Al-4V substrate by laser cladding. Microstructure and wear properties in vacuum (10- 5 Pa) and in atmosphere of the coatings were investigated. Three zones can be distinguished of the coatings: the clad zone, the bonding zone and the heat affected zone of the substrate. The clad zone is formed of undissolved TiC particles, precipitated TiC particles and dendrites, Cr23C6, CrB and TiB2 dispersed in a matrix consisting of primary gamma-Nip and gamma-Nie + Ni3B eutectics. The bonding zone and heat affected zone exhibited small dendrites and acicular martensite, respectively. The wear weight loss of the coatings was 11.4% as that of Ti-6Al-4V alloys in atmosphere, and 47.9% in vacuum. Analysis of the worn surfaces showed that the wear mechanisms of the coatings were abrasion wear in atmosphere, while adhesion wear and ploughed wear in vacuum.