Development of Multi-functional Coatings for Heat Transfer and Wear Protection

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Coatings are used in a plenitude of applications to provide protection to machine parts from the adverse effects of surface degradation processes. Variations of coatings have been developed due to a desire for coatings that do more than provide passive protection. The applicant has identified that the development of new advanced coatings with multi-functional capabilities that extend beyond passive surface protection will offer a unique expansion of the utility of coatings into novel areas that have been established by industry and government. On the blades of wind turbines, ice formation during operation causes the disruption of boundary layers, increases drag, and affects aerodynamic and structural stability. One of the objectives of the proposed research program is to develop and model the heat transfer performance of coatings that will be utilized as resistive heating elements to allow for the mitigation or avoidance of ice accumulation or removal of ice on the blades that are exposed to low-temperature ambient environments. The modelling will focus on the use of heat conduction principles to determine energy generation in an anisotropic porous medium and the determination of the local temperature distribution within the coating during non-Fourier heat conduction due to rapid intense cooling of the coating by high-speed cold water droplets.It is expected that coatings that are exposed to the ambient environment will also be exposed to erodant particles that may cause wear damage of the coating. Thus, in addition to serving as a source of heat energy, the coatings will be developed to be wear resistant. The applicant has developed wear-resistant metal matrix composite (MMC) coatings that possess improved material and mechanical properties such as higher hardness, increased “strengthening effect”, and decreased wear rates. These composite materials are desirable because they offer enhanced properties resulting from the combination and synergies of the properties of both the matrix and the reinforcing materials, such as light weight, strength, stiffness, wear resistance, creep resistance, and improved electrical and thermal conductivity; however, a complete understanding of the mechanisms that result in the increased “strengthening effect” and decreased wear rates of the MMC coating material systems is lacking. The proposed research program will therefore study the microstructure and wear performance of the MMC coatings by conducting a variety of wear tests and modelling the fracture behavior of the coatings to explain the observed wear of the coatings. It is also expected that the inclusion of solid reinforcing particles into the microstructure of the metal matrix of the MMC coatings will increase the effective resistivity or the resistance to electron flow through the coating, thus increasing energy generation in the coating and its effectiveness as a heating element.