Particle impact phenomena of silicon nitride ceramic

By using a new impact test apparatus, the particle impact behaviour of ceramic materials at room temperature and elevated temperatures up to 1400°C and under tensile loads were carried out. Samarium cobalt spheres of 1mm diameter and 4mg mass were used as impact particles. The particle velocities ranged from 200 to 1000ms−1. Silicon nitride, which is a candidate material for gas turbines under development, was chosen as the test material. At elevated temperatures there was a case where the impact fracture strength significantly decreased. At room temperature, the critical impact velocity for crack initiation in thin disc specimens seems to be proportional to (bending strength)5/6 × (thickness)5/3 in line with the results of Tsuruta, Masuda, Soma and Matsui. For particle impact events, electrical signals induced by the impact, photon emission and acoustic waves were observed simultaneously.