An Investigation on SiC and Al Surface Cladding of Ti-6Al-4V for Improved Wear Properties – The Binary Advantage

Abstract

Ti-6Al-4V enjoys high specific strength, toughness and excellent corrosion resistance, but suffers high friction coefficient, severe adhesive wear and sensitivity to fretting wear. Laser surface cladding is one of the surface modification techniques used for improving on these demerits. Laser cladding utilises the high power density available from a focused laser source to heat and melt the substrate’s surface while injecting alloying elements into the melt pool. Using a 4.4Kw continuous wave Nd-YAG laser processor, the surface cladding of as received Ti-6Al-4V alloy was done with mixtures of SiC and Al powders in different ratios. The SiC powder can serve as reinforcing particles and helps improve surface wear properties in the resulting surface metal matrix composite while 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. Study of the cladding with a scanning electron microscope (energy dispersive spectroscopy), optical microscope and x-ray diffraction revealed the formation of intermetallic phases such as AlSiTi₂, Ti₇Al₅Si_12, TiSi₂, AlSi₃Ti₂, Al₆Ti_19, Ti₂VAl, AlTi₃, AlCTi_2, T_i3SiC₂ and Ti₅Si₄, which should enhance micro-hardness and tribological properties of the surface relative to the bulk as-received alloy. 90:10 weight percentage ratio of SiC and Al powder mixture gave the best microhardness with a value of 1169.95 Hv, compared to 323.67 Hv of the as-received, and mass loss under abrasive wear tests was only 40% of the as received. The morphology obtained for the abraded surfaces is also indicative of this improvement. In carefully optimised proportions and laser condition, the binary combination of Al and SiC powders suffice for well improved Ti-6Al-4V surface properties.