Tribological behavior of TiB2-TiC-Al2O3 composite coating synthesized by combined SHS and laser technology

Multi-phase ceramic composite coatings of TiB2-TiC-Al2O3, with an intermetallic phase of TiAl3 were developed by combining self-propagating high temperature synthesis (SHS) reaction of pre-placed TiO2, B4C and Al powders and subsequent laser coating of the products of SHS onto AISI 1020 steel substrate with the help of a high power diode laser (HPDL). The developed composite coatings were characterized by using X-ray diffraction (XRD), field emission gun scanning electron microscopy (FESEM) and micro-hardness measurement. The dry sliding wear behavior of the composite coating was assessed by using a ball-on-disc tribometer at various loads (9.8, 19.6, 29.4 and 39.2 N) and sliding speeds (0.052, 0.104 and 0.156 m/s). The results show that the wear rate increases and coefficient of friction of the coating decreases with increase in normal load. The laser power, laser scan speed employed for production of the coatings and the sliding speeds employed during ball-on-disc tests do not appreciably affect the tribological performance of the coating. However, at high normal loads and high sliding speeds the coatings exhibit rapid wear and suffer from partial removal from substrate.