Effect of dopants on the corrosion behaviour of zirconia by steel at high temperature

Zirconia based material is one of the most interesting materials for semi-solid processing of steel because of its good mechanical properties and high corrosion resistance at high temperatures. In many cases, degradation of zirconia refractories or advanced ceramics is due to unexpected tetragonal-to-monoclinic transformation accompanied by volume expansion. But only little attention was paid to outdiffusion of stabilising additives. In present paper, zirconia based ceramics with different rare-earth oxides (Y2O3 and CeO2) are used in contact with HS6-5-2 steel at 1330 C in order to obtain a good understanding about the corrosion behaviour of high-strength zirconia tool material, especially the effect of yttria and ceria on the corrosion behaviour of zirconia. The results showed that both Y2O3 and CeO2 diffused out of the zirconia structure and formed new compounds with alloying elements of steel at the zirconia grain boundaries. Both lack of stabiliser and grain growth result in t-m transformation and cracks were formed in zirconia ceramic. (orig.)