Microstructure and Dielectric Properties of Thermal Sprayed Aluminum for Electrical Instrumentation Applications

Aluminum oxide coatings show considerable promise for dielectric applications in the electrical instrumentation industry. The dielectric properties of the thermal spray coatings may show a range of dielectric properties depending on many variables including the purity of the powder, thermal spray gun technology (plasma, D-gun), and spray process variables. Thus, it is important to quantify the properties for a given spray condition for our application.

In this investigation, we will be reviewing the aluminium oxide microstructure, mechanical and electrical properties (dielectric strength), as a function of coating thickness and angle of deposition. Part geometries do not always enable 90 degree spray deposition, thus the angle of deposition will be important to review in our study.

Coatings will be deposited onto 75 mm x 25 mm x 1.6mm steel samples. Coating cross-sectioning and image analysis will be performed to evaluate the coating’s microstructure and porosity. Mechanical property measurements will consist of hardness testing on the coating cross sections. In addition, scanning electron microscopy and optical microscopy will be conducted. The correlations between these input parameters and their effect on the microstructure will be important to coating properties for use in electrical instrumentation applications.