This study compares the dielectric properties of annealed forsterite (Mg2SiO4) and alumina coatings deposited on mild steel substrates by atmospheric plasma spraying. As-sprayed coating samples were electrically characterized then submitted to a series of one-hour annealing treatments at temperatures from 300 to 800 °F. After each treatment, impedance measurements were recorded over a frequency range of 30 to 100 kHz. An electrical model was fitted to Nyquist data (Im Z vs. Re Z) using a least-mean-square algorithm with a weighting function. Although impedance spectroscopy measurements were obtained at different temperatures, this paper focuses on the acquisition, modeling, and comparison of room temperature properties, particularly electrical resistivity and dielectric constant. It also compares the microstructure of as-sprayed and annealed forsterite and alumina coatings and discusses coating degradation mechanisms stemming from differences in CTE.

This content is only available as a PDF.
You do not currently have access to this content.