Problems on the development of hard and low friction in-situ coatings on Ti-6Al-4V using laser cladding

Coatings having high hardness and low coefficient of friction are significant for long service life of engineering components subjected to sliding wear. Some useful applications of such coatings are in various engine components including aerospace industries. Laser surface engineering has promising process characteristics for changing surface properties. In this concern, using laser cladding process hard and low friction coatings were developed on Ti-6Al-4V for improving sliding behavior of its components. To carry out the experimental investigations, the pre-placed powder mixture of B4C, hBN and Ti were used on the Ti-6Al-4V substrates and subsequently laser irradiated to form the improved surface properties. The coatings were developed with a wide range of laser scan speeds. Physical and mechanical characterizations of all samples were done rigorously. For some laser-scan-speeds in the range of studies, developed coatings resulted in very high hardness about 2200 HV. The dry sliding wear tests (against WC ball at 10 N loading) indicated a very low coefficient of friction of about 0.1 to 0.16 for the coatings. The problems experienced during development of the in-situ coatings are highlighted in the paper.