Direct laser cladding of Co on Ti-6Al-4V with a compositionally graded interface

Abstract

In the present study, attempts have been made to fabricate Co layers on the surface of Ti-6Al-4V substrate with a compositionally graded interface by direct laser cladding. Laser processing is carried out by pre-placing the powder (or powder blends) on the substrate, and melting it using a high power continuous wave CO₂ laser with Ar as shrouding gas. A compositionally graded interface is developed by applying powder blends of Ti to Co at a ratio of 90:10 near to Ti-6Al-4V substrate to 10:90 prior to development of Co layer. A defect-free microstructure is developed with the presence of Ti₂Co and TiCo and Co₂Ti at the interface. The volume fraction of individual phase was found to vary with the depth from the Co-clad zone. A significant improvement in microhardness is achieved at the interfacial region. Uniform corrosion resistance increases along the graded interface, but the pitting corrosion resistance is marginally deteriorated. Direct laser clad layer possesses a better biocompatibility than that of as-received Ti-6Al-4V sample.