抄録
A novel technique in which pulse laser irradiation is used to improve residual stress of material surface has been developed. When a material surface is irradiated by a high-energy pulse laser, the impulsive wave, which is generated by the high-pressure plasma, propagate into the material interior, thereby inducing high compressive stress on the material surface. The stress improvement for Type 304 stainless steel was evaluated to apply it to reactor internals in light water reactors as a preventive maintenance technique. Remarkable stress improvement was obtained for Type 304 stainless steel, the thickness of a compressive stress layer was much larger than that in the case of conventional peening techniques, and the compressive stress depth profiles virtually independent of the material strength (cold working rate). The effects of processing parameters, i.e., spot diameter, pulse energy and pulse number density, on the stress improvement of Type 304 stainless steel were investigated. It was also confirmed from metallographical structure and AES analysis that there was not much thermal effects on the material due to the laser irradiation.
