Fatigue Crack Propagation in a Type 304 Stainless Steel Weldment

Abstract

The present work is the initial part of a broadly based investigation of the fatigue crack propagation in a Type 304 stainless steel welded joint. In particular, attention is focussed to the fatigue crack growth behavior of the cross-bond type crack, the front of which is inhomogeneous and consists of two regions; one is the weld metal region and the other is the base metal region.
Although effect of residual stress on fatigue crack growth rate was quite significant, that of microstructure of the weld metal was also found to be significant: The growth rate of a weld metal specimen was larger than that of a base metal specimen when the growth rate was plotted against effective stress intensity range. The effect of residual stress on fatigue crack growth rate can be found even after the solution treatment (1050°C for 1.5 hr). Hence, it may be conservative to consider that after usual PWHT, residual stress which can have an effect on fatigue crack growth rate is still remaining. For the cross-bond type specimens, it was found that the cracks in the two regions did not interact each other and propagated independently in each region: The fatigue crack in the weld metal region propagated faster than that in the base metal region.