Estimation of thermal shock strength of Cr3C2 ceramics by laser irradiation

Nuclear power plants have the greatest potential for use in space ships, underwater vehicles, and so on. Because the space and the weight for those plants have limitation, it is very important to develop new radiation shielding materials which have excellent mechanical strength and heat-resistant characteristics. Chromium carbide ceramics (Cr3C2) is the neutron absorber which is more excellent than titanium boride ceramics and has been investigated as a radiation shielding material. This report presents an evaluation of thermal shock strength by the laser irradiation technique for chromium carbide ceramics. Their temperature and thermal stress distributions are analyzed by the finite element method (FEM), and critical fracture curves, which can specify a critical power density for a given laser beam spot diameter, are obtained from the relationships between the spot diameter of the laser beam and the maximum tensile thermal stress. And furthermore, size effects to the fracture criterion of chromium carbide ceramics are examined, and the laser irradiation experiments are performed on chromium carbide ceramics using a CO2 laser. Finally, theoretical results are compared with experimental ones, and the thermal shock strength PL of Cr3C2 ceramics with laser irradiation is ∼3.4 W/mm2 for tension by the FEM analyses. (author)