Comparative responses of welded joints to surface mechanical attrition treatment and shot peening

Abstract

Responses of welded joint of carbon steel to surface mechanical attrition treatment (SMAT) and shot peening (SP) were investigated. Experimental evidences showed that the microstructure of treated surface in the welded joint by means of SMAT was characterised by nanometre grains of about 13·6 nm in size and that of SP was characterised by highly dense dislocation configuration. The similar microhardness profiles with different peak values in the top surface were observed for three typical zones of welded joints processed by SMAT and SP. Compared with as welded specimens, SMAT and SP processes have improved the fatigue strength by as much as 61 and 36·3% respectively based on fatigue life 2×10⁶ cycles. The observed enhanced fatigue behaviours of the welded joint processed by SMAT and SP should be attributed to the combined influences of compressive residual stress, work hardening, nanostructure and elimination of microdiscontinuities in the vicinity of welded joints.