Electrical resistivity of thermally sprayed Cr2O3-TiO2 coatings

In this study, the influence of spray parameters on the elec. resistivity of thermally sprayed ceramic coatings from the system Cr2O3-TiO2 was investigated. Fused and crushed feedstock powders with contents of 10 wt. % and 20 wt. % chromium oxide were deposited by APS and HVOF. Temp. and velocity of the particles in the spray jet as well as the coating surface temp. were analyzed during the deposition process. Impedance spectroscopy was used to investigate the elec. resistivity of the coatings and the results were correlated to coating microstructure and phase compn. It was found that phase transformations occur during the spray process. In the coatings a high temp. phase (n-phase) and rutile were obsd. Though, the ratio of rutile depends on the spray methods employed for coating dep osition. The elec. resistivity of coatings obtained by HVOF can be correlated to the content of chromium oxide. Furthermore, the surface temp. of the coating during deposition also shows some influence. Concerning the coatings resulting from APS, the different mixts. of the plasma gases (Ar-H2 and Ar-N2) are supposed to have the most important influence on the elec. resistivity.