Microstructure and mechanical properties of laser-cladded WC–Co composite coatings on Ti–6Al–4V

Abstract

WC-Co powder reinforced coatings were prepared on the Ti-6Al-4V substrate for improving the hardness and wear resistance by laser cladding technique. The effects of different laser power and Co content on the microstructure and properties of the cladding layer were studied. The results showed that when the laser power was too low, there were unmelted WC-Co powders on the surface of the cladding layer. In contrast, when the laser power was too high, the coating materials were prone to over-burning and evaporation, cracks and pores were aggravated. The WC-25Co coatings without cracks and pores could be formed when power is set at 1300 W, and its average micro-hardness was higher than other specimens. The addition of Co was helpful to the bonding of clad and Ti-6Al-4V substrate. New hard phases of TiC and CoTi2 were mainly distributed in the cladding coatings. The micro-hardness of the cladding coatings increased by 2–4 times than that of the Ti-6Al-4V substrate, and the maximum hardness reached 1349 HV. Under the same dry sliding wear condition, the wear resistance of the WC-25Co coatings was significantly improved and increased by 15.7–34.1 times compared with the substrate.