Microstructure and wear properties of laser cladded cBN/Ti3Al on pure titanium

Abstract: In order to improve the tribological properties of titanium alloys at high temperature, the possibility of producing Ti3Al intermetallic with the addition of ceramics (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 (SEM) with EDX was used for characterizing 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, Ti2N and TiB2 peaks in addition to the rich γ-Ti, α2- Ti3Al 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 form of dendrites, precipitate of α2- Ti3Al and spherical shaped pure titanium. The effect of the addition of cBN into Ti3Al 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