Microstructural and tribological properties of plasma sprayed chromia alloyed with different oxides

Plasma spraying was used to deposit different chromia based coatings under identical spray parameters. The compositions of the coatings manufactured were pure chromia, chromia-titania, chromia-alumina and chromia-zirconia. The behaviour of the different powders in the plasma spray process were investigated. The powders and the coatings manufactured were investigated and compared with each other. Powder feedstocks microstructure, phase and chemical composition and size distribution were studied. Coatings characterization was as a first step focussed on their microstructure and denseness (FEG-SEM, XRD). Coating hardness was also measured. Tribological investigation included sliding wear (with two different counterparts, alumina and zirconia) and abrasion wear tests, according to ASTM G99 and G105, respectively. Wear rates were measured by weight loss and optical profilometry. Wear mechanisms were investigated by FEG-SEM and Raman spectroscopy. Further investigation was carried out by TEM analysis of the wear debris.