Alternative to chromium: characteristics and wear behavior of HVOF coatings for gas turbine shafts repair (heavy-duty)

Hard chromium plating is usually used to restore to original dimensions the worn surfaces of gas turbine shafts. However, such a technology presents harmful effects on the environment and the public health and it exhibits, moreover some intrinsic technical limitations. HVOF (high-velocity oxy-fuel) thermal spraying process appears as more environmentally friendly than chromium plating process but exhibits also lower potential production costs when compared to hard chromium deposits. In such a way, HVOF process appears as an alternative to hard chromium plating for shafts repair, by reducing the frequency of maintenance operation and repair and by deferring the need to fabricate or to buy replacement parts for used engines of previous generation. The purpose of this study was to investigate and to compare microstructural properties, wear resistance, and potentials of HVOF sprayed Tribaloy©-400 (T-400), Cr3C2–25%NiCr and WC–12%Co coatings for a possible replacement of hard chromium plating in gas turbine shafts repair. It was shown that thermal spray coatings exhibit the adequate properties compared to electrodeposited hard chromium coatings.