An Experimental Study of the Performance of Flame-Sprayed Ni-Based Metal Matrix Composite Coatings as Resistive Heating Elements

The growing need for developing efficient surface heating systems in aircraft manufacture and renewable energy industries necessitates further enhancement of functional coatings developed to serve as heating elements. In this study, nickel-chromium-aluminum-yttrium (NiCrAlY) powder was chosen as the matrix and was mechanically admixed with three different ceramic powders namely, alumina, titania, and tungsten carbide, to produce the feedstock metal matrix composite (MMC) powders for deposition on carbon steel substrates. For the purpose of electrical insulation of the substrate, a layer of alumina powder was deposited prior to fabricating the MMC coatings in order to prevent short circuiting. A number of Joule heating experiments were conducted by supplying certain voltages to the coatings and measuring the surface temperature distribution of the elements. The effect of electrical resistance and dielectric behavior of the ceramics on the performance of the heating elements was investigated. It was observed that the heat that was generated in the coating heating elements was considerably affected by the electrical properties of the ceramics. The experimentally obtained data suggest that manipulation of the feedstock electrical properties and modification of the cross-sectional morphology of the coatings may be implemented to improve the functionality and heating performance of the heating elements.