Dry sliding wear behaviour of binary powder laser cladded Ti-6Al-4V using SiC and Al

Abstract

High specific strength, toughness and excellent corrosion resistance are some of the outstanding qualities of Ti-6Al-4V. However, it suffers from unstable friction coefficient, severe adhesive wear and sensitivity to fretting wear. Laser surface cladding is a vital process for alleviating on these surface challenges. The SiC powder can serve as reinforcing particles and helps improve surface wear properties in resulting surface metal matrix composite. However, SiC wets poor with the alloy pool, impacting negatively on the quality of the surface. Powder admixtures have been used to counter this effect. This work aims to study the impact of binary powder compositions on the wetting of the laser melt pool as inferred from the laser cladded surface properties. Aluminium improves on the wetting between the metal and the reinforcement SiC phase. The success of this, however, depends on the careful optimisation of the powder ratio, which dictates the resulting phases and microstructural evolutions. The scanning electron microscope (energy dispersive spectroscopy), optical microscope, and x-ray diffraction were employed in the characterisation of the cladded layers. The results revealed the formation of intermetallic phases such as Ti5Si3, Ti5Si4, and Ti7Al5Si12, which should enhance micro-hardness and tribological properties of the surface relative to the bulk as-received alloy. The cladded surfaces had a stable and consistent friction coefficient values relative to that of the as received because of the formation of stable surface oxides. In carefully optimised proportions and laser condition, the binary combination of Al and SiC powders suffice for well improved Ti-6Al-4V surface properties.