Study on fatigue strength improvement of nuclear turbine by laser peening

Abstract

Some damage was found at the forks of low-pressure turbine blades caused by steam-flashback vibration at nuclear power plant. As countermeasure against vibration during operation, laser peening for turbine blade was investigated and effectiveness was evaluated by material tests. 12 Cr stainless steel test pieces with pin hole were fabricated and laser peening was performed on the surface. As the result of material evaluation, it was confirmed that compressive residual stress was induced to the material surface by laser peening and fatigue strength was improved about 30% compared to unpeened test pieces. In the near future, laser peening will be applied to turbine blades to improve plant reliability.