Reduction of Cr6+ formation in the stellite hardfacing operation by a novel thin film of zinc coating on a stellite filler rod

In the widely known welding procedure called “hardfacing,” a substrate material is covered with extra material to provide wear and corrosion-resistant properties. Cr is the major alloying element in Stellite-6; it forms Cr 6+ in the weld atmosphere through oxidation in the presence of ozone. The current study aims to reduce the Cr 6+ emission during stellite hardfacing by coating a thin film of zinc on the stellite filler rods using the electrogalvanizing process. A reduction of up to 90% in Cr 6+ formation was achieved through this operation. Using the response surface methodology of design of experiments (DoE), the finer interaction effects of the process parameters that supported the highest decrease of Cr 6+ emission were examined. A homogenous morphology and lower crystallite size of zinc coating favored the effective participation of Zn during oxidation due to higher surface area.