The effect of strain strengthening on the mixed mode crack fatigue propagation in the HAZ of 06Cr19Ni10 stainless steel

The present study focuses on the mixed mode fatigue crack propagation in the HAZ of 06Cr19Ni10 stainless steel. The effects of strain strengthening on crack growth path, crack growth rate, residual stress and microstructures were analyzed separately. The results of crack propagation test show that a new fatigue crack initiated from pre-crack tip and propagated along a line perpendicular to the loading direction. It is noted that strain-strengthening could reduce the crack growth rate but it has no effect on crack propagation path. Strain strengthening can produce stress-induced martensite and the martensite volume fraction increases with the strain-strengthening level. Finite simulation analysis and experiment results show that residual tensile stresses of HAZ can be reduced significantly by strain-strengthening treatment.