Microstructure and Wear Properties of Laser-Cladded cBN/Ti ₃ Al on Pure Titanium

In order to improve the tribological properties of titanium alloys at high temperature, the possibility of producing Ti₃Al intermetallic with the addition of ceramic (cBN) coatings on titanium substrate using laser technique cladding was investigated. cBN is generally known for its high hot hardness, wear resistance and chemical stability. Laser cladding is an emerging material processing technique which is an efficient and cost-effective technique for improving the surface properties of general metallic materials. This paper presents the effects of laser cladding on the phase combination, microstructure, hardness and wear resistance of titanium aluminide/cBN IMC composites at different variations in quantity of cBN in the composite. Optical microscopy, X-ray diffraction and scanning electron microscopy with EDX were used for characterising the microstructure of the coating. In addition, the composite coating was subjected to wear testing using the ball-on-disc, friction and wear apparatus. The XRD results revealed phases with small cBN, Ti ₂N and TiB ₂ peaks in addition to the rich γ-Ti, α2 -Ti ₃Al and TiAl intermetallics phases in the coatings after cladding process, whereas the microstructure of the cBN cladded layer contained partially melted cBN grains evenly dispersed within the laths of alpha Widmanstätten phase in the form of dendrites, precipitate of α₂-Ti ₃Al and spherical-shaped pure titanium. The effect of the addition of cBN into Ti ₃Al alloy at increasing weight percentages showed an improvement in the hardness and wear resistance of the coatings. The increase is attributed to reacted boron nitrides particles with titanium, being distributed uniformly in the intermetallic matrix.