The effect of laser shock peening on stress corrosion crack behavior of laser welded ANSI 304 stainless stail and microstuctral characterization

By using Nd: YAG laser welding system, 2 mm thick 304 stainless steel was welded in bead-on-plate configuration in three different levels of three factors; these are peak power, welding speed and pulse duration. The multi-response optimization problem was developed to reveal the quality characteristics of the weld geometry and the grey relational analysis based on the Taguchi method was used to provide an effective approach in optimization. The developed regression equations were tested for values ​​different from the levels of the parameters in the orthogonal array. The welded materials were characterized in terms of microstructure and mechanical properties. A linear relationship has been found between the crater and heat input. However, the gradual increase in heat input is not directly related to penetration. At the highest heat input, the weld beads have expanded significantly and the crater has deepened, while the hardness in this area has increased, and the tensile strength and ductility have decreased. Laser energy has increased the ferrite network, creating finer ferrites. Usable laser welding parameters for welding of 2mm 304 stainless steel have been identified in terms of good strength, ductility and weld bead morphology. In the last section, the influence on the microstructural development, mechanical properties and stres corosion cracking SCC of laser shock peening LP (with and without coating) laser-welded samples has been presented. SCC behavior was examined in air and in solution (3,5 % NaCl+0.5mol/L H 2 SO 4 ) with slow-strain rate test. Microhardness profiles, microstructures were examined and compared. The LPed surface was analyzed using the X-ray diffraction method. The results show that LP without coating is an effective method to increase the SCC performance as well as increase the microhardness of the surface layer. These developments have been shown to correlate with the strain hardening effect resulting from high-strain plastic deformation in the formation of dense deformation bands. The results also show that the effects of LP treatment on the SCC susceptibility index depend on martensitic phase transformation in the base metal. Tensile residual stress on the surface represents the thermomechanical effect of LP without coating. LP without coating process shows a combined effect of thermal and mechanical effects on the material, it is an effective and useful method in terms of both mechanical and corrosive behavior.