Stress-Relief Cracking

What Does Stress-Relief Cracking Mean?

Stress relief cracking occurs when susceptible alloys are subjected to thermal stress after welding to reduce residual stresses and improve toughness.

Stress-relieving is the process generally specified after welding of most materials. Removing or reducing the residual stresses generated by welding is required for improving the dimensional stability of weldments. Stress-relieving occurs by diffusion of atoms within solid materials.

Stress-relief cracking occurs only in metals that can precipitation-harden during such elevated-temperature exposure. It usually occurs at stress raisers, is intergranular in nature, and is generally observed in the coarse-grained region of the weld heat-affected zone.

Stress-relief cracking is also known as post-weld heat treatment cracking.

Corrosionpedia Explains Stress-Relief Cracking

Stress-relief cracking is a major cause of weld failures in creep-resistant, precipitation-strengthened materials such as ferrite alloy steels, stainless steels, and Ni-based super alloys. Stress-relief cracking occurs primarily in the coarse-grained heat-affected zone of weldments.

Although the general causes of stress-relief cracking are known, different metals or alloys exhibit different types of stress relief mechanisms, but the general underlying mechanisms still unknown. The mechanism of stress-relief cracking in the coarse-grained heat-affected zone (CGHAZ) of a material can be investigated through stress-relaxation testing and detailed micro-structural characterization.