Thermally sprayed metal matrix composite coatings as heating systems

Abstract

• Thermally sprayed metal matrix composite heating elements were developed and tested. • Effect of ceramic reinforcement on heating performance of the coatings was studied. • Electrical properties of the coatings noticeably affected their heating rate. • A heat transfer model was developed to predict the coating temperature distribution. Wind turbine blades and aircraft wings operating in extreme cold environments are prone to severe ice accretion. The accumulated ice may cause aerodynamic deficiency, lower durability, power losses, and significant safety issues. This study introduces a novel coating-based heating system that takes advantage of a certain group of materials, namely, metal matrix composite (MMC) coatings. With nickel chromium-aluminum-yttrium (NiCrAlY) as the metal matrix, coatings with different ceramic and cermet reinforcing phases were fabricated to produce electrical heating elements. The effects of coating microstructure and ceramic phases on the electrical properties and electrical resistance of the heating elements were examined. In order to assess the heating performance, a number of Joule heating experiments were conducted on the fabricated coatings. It was observed that MMC coatings with dielectric or semi-conductive reinforcing phases had considerably higher electrical resistance, heating ramp-up rate, and steady state temperature. A 2-dimensional transient heat conduction model with energy generation at the upper layer was developed to predict the temperature distribution in the multi-layered coating system. A similar heat conduction problem was simulated using ANSYS Mechanical software. The simulated results and that of the analytical model were in good agreement with the experimental data. The results of this study suggest that implementing ceramic reinforcements into MMC coatings will result in significant improvements in heating efficacy, and reduce consumption of energy in coatings-based de-icing systems.