SURFACE STRENGTHENING OF ALUMINA-ZIRCONIA COMPOSITE BY ADDITION OF MOLYBDENUM DIOXIDE

MoO2 is found to stabilize m-ZrO2. Because of the addition of MoO2 int o ZrO2 at the surface region of an Al2O3-15 vol% ZrO2 composite, the v olume fraction of m-ZrO2 at the surface increases from 0.3 to 0.5-0.6 without changing the size of the ZrO2 grains. This enhanced transforma tion results in an increase in flexural strength of up to 30% because of compressive stresses built in at the surface. The increase in flexu ral strength is proportional to the difference in volume fraction of m -ZrO2 between the surface layer and the bulk matrix, in agreement with a previous analysis.