Influence of ZrO2 additives on properties of Mo-Al2O3 cermets

To improve the strength of the Mo-Al2O3 cermet, effect of 1.0 wt% similar to 5.0 wt% ZrO2 addition on mechanical propertied of the cermet was investigated. The results show that when ZrO2 addition below 3.5 wt % the bending strength of the cermet was improved with increasing of ZrO2 addition. The cermet containing 3.5 wt% ZrO2 addition showed the excellent strength, while the strength had a tendency of decreasing if ZrO2 addition was a little more. The grain size of the cermets with 4 wt % ZrO2 was a little bit larger than those of the cermets without ZrO2, but the additive has no influence on the oxidation property. Under the condition of nitrogen protection, the service life of the protective pipe of thermocouple made of ZrO2 containing Mo-Al2O3 cermets at 1700 degrees C will be doubled comparing with those of the cermets without ZrO2.