Effect of nano-sized TiC powder on microstructure and the corrosion resistance of WC-Co thermal spray coatings

In this article, the electrochemical behavior of HVAF WC-17Co coatings modified with TiC deposited on low alloyed steel substrates was investigated. As a reference for coating material a commercial WC-17Co powder was used. The WC-17Co feedstock powder modification process was based on the addition of nano-sized TiC (weight ratio from 1 to 7%) by mechanical mixing. The aim of the research is comparing the microstructure and some selected properties of HVAF coatings with different amounts of TiC. The preliminary characterizations concerned the coating porosity, phase composition and microstructure. Then a corrosion resistance for all variant of coatings was evaluated by electrochemical polarization tests at room temperature in 3.5% NaCl and 0.5 M H2SO4 solutions. The results showed an evident influence of nano-sized TiC addition on both on the corrosion resistance and the electrochemical properties of WC-17Co coatings. In the case of investigation in 3.5% NaCl, addition of nano-sized TiC caused shifting polarization curves in more noble range, however in 0.5 M H2SO4 solution no significant changes in corrosion behavior were observed. Addition of nano-sized TiC significantly decreases corrosion resistance of WC-17Co + TiC coatings.