POST WELD HEAT-TREATMENT EFFECTS ON FATIGUE-CRACK PROPAGATION IN AN ELECTRON-BEAM WELDMENT

This paper studies the effect of two post-weld heat treatment processes on the fatigue behaviour of an electron beam weldment in 9 mm AISI 4130 steel. Electron beam tempering, in a vacuum chamber, immediately after welding and a traditional furnace tempering treatment were compared. Fatigue crack propagation resistance was assessed by a linear elastic fracture mechanics analysis. The resistance to fatigue crack growth was improved with post weld heat treatment due to residual stress relief and the existence of a toughened tempered microstructure. The specimens with an electron beam post-weld heat treatment showed better fatigue properties than those of furnace-treated specimens. An electron beam post-weld heat treatment causes the fatigue crack growth rate to decrease with increasing energy input and decreasing micro-dot-pattern width. For a furnace post-weld heat treatment, the fatigue crack growth rate decreases with increasing tempering temperature.