Control over the Porosity of Plasma Sprayed Aluminum Oxide Parts by Heat Treatment

Abstract

We have examined the feasibility of controlling porosity in the material of pure alumina parts produced by plasma spraying. To this end, we studied samples before and after heat treatment under various conditions. Porosity was determined by computed tomography and scanning electron microscopy. The phase identification and quantification were done by X-ray diffraction. The porosity of the material of pure alumina parts produced by plasma spraying was shown to vary nonmonotonically with heat treatment temperature and to be influenced by the temperature-induced polymorphic transformations of alumina. The material was shown to consist of different alumina polymorphs, which underwent polymorphic transformations, accompanied by volume changes, during heat treatment. The opposite changes in the volume of the phases involved are responsible for the nonmonotonic variation of the porosity of the material with heat treatment temperature. The observed behavior of porosity is well reproducible. This suggests that heat treatment can be used to control the porosity of pure alumina parts produced by plasma spraying.