Influence of laser peening processing on SCC sensitivity in weld joint of 304 type stainless steel

In order to prevent stress corrosion cracking (SCC) of austenitic stainless steel weldment, a novel technique-laser peening-has been introduced which is able to convert surface tensile stresses in the weldment to surface compressive stresses. In this paper, water-immersed welding specimens of type 304 stainless steel are peened by Q-switched Nd: glass laser with a wavelength of 1.06 μm. A residual compressive layer is produced on the specimen surface by scanning laser pulse to cover the heat affected zone (HAZ) along the weld line based on X-ray measurement. The SCC accelerated tests for comparing the potential against SCC of the specimens, which are unpeened and peened by laser pulse with different laser spot coverage, are carried on. The results show that stress corrosion cracks on the surface of unpeened specimen occur after immersion for 25 hours in the boiling 42% MgCl² at 143°C solution. In contrast, the specimen with 45% laser spot coverage cracks after immersion for 300 hours, while, cracks are observed on the surface of laser-peened specimen with 80% laser spot coverage after 985 hours of testing. The results from experimental data show that laser peening is an effective technique for improving the residual stress distribution and the SCC resistance of 304 stainless steel weldments in chloride solutions.