Characteristics, composition and structure of coatings of WC-TiB2-B4C - Ni-Cr-B-Si-C electrodes formed on titanium alloys by contactless electrospark deposition

Abstract

The aim of the work is strengthening of titanium surfaces and increase of their wear resistance by using a cheap and simple method - local contactless electrospark deposition LESD with a cylindrical rotating around its axis electrode. A new type of multicomponent coatings of We-based hard-alloy electrodes with additives of B4C and TiB2 and a bonding multimetallic mass of Ni-Cr-B-Si-Fe-C was created. The influence of process parameters and ratios between individual electrode components on the roughness, thickness, composition, structure and tribological characteristics of the coatings was studied by metallographic, profilometric, XRD, SEM, EDX and tribological methods. Dense and uniform coatings with new relief and newly formed wear resistant phases and crystal-amorphous structures were obtained. It was found that the roughness and thickness of the coatings can be varied by LESD modes in the ranges Ra =1.3÷3µ m and δ=6÷22 µm, respectively. Their microhardness ranges from 9 to 14 GPa and their wear resistance is up to 4 times higher than that of titanium substrates. It was determined the mode parameters and electrode compositions at which maximum wear resistance of the coated surfaces was obtained. The resulting dependencies enable controlling the roughness, thickness, composition and properties of coatings and significantly improving titanium surfaces.