Parameter Development for HVAF Sprayed Al0.5CoCrFeNiZr0.5Si00.2 High-Entropy Alloy Heating Coatings

This study investigates the parameter development of High Velocity Air Fuel (HVAF)-sprayed Al0.5CoCrFeNi and Al0.5CoCrFeNiZr0.5Si0.2 high-entropy alloy (HEA) coatings for use as resistive heating layers. A design of experiments was applied to evaluate the effects of spray distance and nitrogen carrier gas flow rate on coating morphology, mainly porosity and oxidation. Overall, low spray distances and moderate gas flow rates were found to be favorable for deposition efficiency and dense coatings with porosity below Φ < 0.4 % are achieved for the novel Zr- and Si-containing alloy. Oxidation however, mainly in the form of interlamellar oxides, is identified as a point of concern in these alloy systems. They primarily consist of Al and Zr oxides and occur across all parameter sets. The impact of these oxides on the electrical properties and subsequent heating performance must be evaluated and methods must be tested to further reduce the oxygen content.