Effects of surface qualities on corrosion performances of X80 pipeline steel welded joints by laser shock processing

The surface of X80 steel pipeline welded joint was processed with laser shock processing (LSP),and the microstructure and roughness of welded joint before and after LSP was analyzed with metallographic microscope and optical profilometer, respectively. The changes of residual stress and residual austenite of welded joint before and after LSP were measured with stress tester,the mechanism of improving the surface qualities of welded joint by LSP was also discussed. The results show that the grain refinement of X80 pipeline steel welded joint is produced by LSP,the surface roughness has increased a little. The compressive residual stress is formed by LSP,and residual austenite is transformed into martensite. The effect of surface roughness and residual austenite by LSP on its tension performances is a main factor,its inner product power decreases 3.8%. The sensitivity index ISCC of stress corrosion of the sample by LSP decreases from 50.94% to 45.10%,the compressive residual stress and refined grain are the main mechanisms of affecting its stress corrosion resistance.