Influence of Surface Mechanical Attrition Treatment on Microstructure and Properties of X80 Pipeline Steel Welded Joints

X80 pipeline steel weld joints were subjected to surface nano-crystallization for 30,60 and 90 min by using surface mechanical attrition treatment (SMAT) technology,and the changes of the microstructure,grain size,surface roughness and the micro-hardness were examined by using OM,XRD,roughmeter and hardness tester.The results show that the plastic deformation layer with a certain thickness could be achieved at the surface of X80 pipeline steel welded joints after SMAT for different times.The thickness of plastic deformation layer increased with the increase of the SMAT duration.The nano-crystallization could be realized at the surface of X80 pipeline steel welded joints.The surface microhardness and roughness of X80 pipeline steel welded joints were also significantly improved by SMAT.The microhardness showed a gradient distribution in the thickness direction and the roughness decreased with the increase of the SMAT duration.