Effect of laser shock peening on the microstructure, tensile and heat transport properties of Alloy D9

Present work investigates the effect of laser shock peening on the microstructure and properties of alloy D9, a candidate material for the core applications in fast breeder reactors. For select peening parameter, surface and depth distribution of residual compressive stresses, microstructure, hardness, tensile properties and thermal diffusivity have been compared with a reference (annealed) material. After shock peening, using laser energy of 3J/pulse, compressive stresses were present up to a depth of 360 μm from the surface with a maximum magnitude of 330 MPa at a depth of 20-30 μm from the surface. Though the microstructure showed no appreciable change, both hardness and yield strength increased (by 32% and 63% respectively) and ductility decreased after peening. Mechanical property evaluation using miniaturized tensile testing gave a truly quantitative estimate of the change in properties due to peening. Change in thermal diffusivity measured from ambient temperature up to 700 °C suggested the superior thermal stability of laser shock peened specimen.