Effects of Mullite Coating on Mechanical Properties of Alumina Component

The prestressing reinforcement has been proved to be effective for ceramics, but how this surface prestressing affects other mechanical properties is still unclear. The influence of surface residual compressive stress on the mechanical properties of composite members, including bending strength, elastic modulus, fracture toughness, hardness and damage tolerance are investigated in this work. In order to achieve suitable surface compressive stress and the appropriate interface shear stress, mullite and aluminum oxide are mixed and ground into a slurry with a mass fraction ratio of 1∶1 and coated on the pre-sintered alumina substrate. The coated samples were prepared by pressureless sintering. With the temperature drop, different shrinkage rates and interface constraints of the two materials form the residual compressive stress in the surface layer. Mechanical properties of the coated alumina were tested. The experimental results show that the prestressed design can effectively improve the bending strength of alumina by 38.9%; The fracture toughness is increased by 36.5%, and the elastic modulus and hardness are slightly decreased. The damage tolerance of the prestressed ceramic is increased from 0.3894 m^1/2 to 0.4527 m^1/2, which is 16.26% higher.