HVOF Applied ‘Flash’ Coatings for Hard Chrome Replacement Applications

Conventional HVOF hard metal or carbide coatings have been used for hard chrome replacement for many years in applications such as hydraulic rods, actuators and similar components for oil and gas, mining, and aircraft landing gear. However, the cost of such HVOF coatings is higher when compared to electroplated hard chrome for several reasons including the material cost, greater thickness and post-deposition finishing requirements. Chrome electroplating does have negative environmental implications compared to HVOF due to hexavalent chromium toxicity and is heavily regulated which threatens its future as a low cost coating solution. Recently, so-called ‘flash carbide’ coatings using HVAF have emerged as potential solutions which are more cost-effective than conventional HVOF coatings as they are thinner and smoother with low porosity. In this work, the feasibility of depositing flash type coatings using HVOF is compared to HVAF including different material types, spray metrics, coating microstructure and wear/corrosion performance. Some preliminary aspects of coating finishing are addressed in addition to application specific requirements.