Mechanical Properties and Contact Damages of Nanostructured Silicon Carbide Ceramics

Abstract

Three types of nanostructured silicon carbide ceramics were prepared with additives of Al2O3 and Y2O3 as the primary sintering additives, together with 1 mass% CaO, 1 mass% MgO or 0.73 mass% AlN. The silicon carbides (SiC) containing tens of nanometers of grains were successfully fabricated using a two-step sintering process. The mechanical properties and contact damages of the nanostructured SiC ceramics were investigated in this study. The nanostructured SiC ceramics exhibited a hardness of~20 GPa, a strength of 400-700 MPa, and a toughness of 3.0 MPa•m1/2. The nature of the contact damage exhibited classical ring or cone cracks formed in a region of weak tension outside the contact rather than microcracks in the diffuse quasi-plastic zones as observed in heterogeneous microstructures consisting of micron-sized elongated grains.