Indentation properties of silicon carbide after neutron irradiation and helium implantation

The hardness, elastic modulus and fracture toughness of the CVD-SiC after neutron irradiation up to 0.4 dpa at 600°C and up to 0.6 dpa at 800°C and after He implantation up to 800 appm at 750°C were evaluated using the indentation technique. The effect of neutron irradiation was discussed with the previous data (0.2-7.7 dpa, 80-1050°C). The hardness slightly increased at all neutron irradiation doses and temperatures. It was independent on the neutron irradiation dose above a saturation value. Almost no influence of the He implantation on the hardness was observed. The rapid reduction of elastic modulus with the neutron irradiation temperature below 100°C was observed. However, it gradually recovered and showed almost the same value as the unirradiated one when irradiated above 800°C. About 35% reduction of the elastic modulus due to He implantation was observed. Small reduction of fracture toughness below 400°C, and increase with increased neutron irradiation temperature to 1000°C was observed. About 30% reduction of the fracture toughness due to He implantation was observed, which was mainly attributed to the reduction of elastic modulus and the increment of crack length under indentation.