Abstract
Alumina is a relatively low-cost material and easily processable by thermal spraying into wear and corrosion resistant coatings. However, thermally sprayed alumina coatings show inferior corrosion resistance versus chromia coatings, particularly in low and high pH electrolytes. Further, alumina possesses decreased mechanical properties in the as-sprayed state. In the present study, the effect of chromia addition on the properties of the plasma and HVOF sprayed alumina coatings were studied. Pure alumina powder and four different Al2O3-Cr2O3 powders were prepared in two different atmospheres and produced to coatings with APS and HVOF methods. Phase composition of the powders and coatings were studied by X-ray diffraction. Electron microscopy was used for the examination of the microstructure of the powders and coatings. The mechanical properties of the coatings were studied by hardness and abrasion resistance tests. The chemical properties of the coatings were examined by corrosion exposure tests. Results indicate that with chromia addition it is possible to improve the mechanical and chemical properties of the thermally sprayed alumina coatings.
