The Influence of Hot Isostatic Pressing on the Phase Composition and Porosity of Plasma-Sprayed Ceramics of Pure Alumina

The changes in the phase composition and porosity of plasma-sprayed Al₂O₃ ceramic before and after its treatment by hot isostatic pressing (HIP) have been studied. The treatment was performed using a HIP facility with a graphite resistance heater in an argon atmosphere at a temperature of 1600°C at a gas static pressure of 200 MPa for 3 h. The phase composition of the material was determined using quantitative phase analysis. The porosity of the ceramic was determined by X-ray computed tomography. It has been established that, just at the end of plasma spraying, the ceramic material contains a set of α-, γ-, and δ-modifications of Al₂O₃, which differ in the density and type of crystal lattice. The total ceramics porosity was 18.9 vol %. After treatment using HIP, the metastable γ- and δ-Al₂O₃ phase modifications disappeared, and the stable α-Al₂O₃ modification occupied the entire volume of the ceramic material. The total ceramics porosity decreased to 9.7 vol %.