Delayed cracking in 301 austenitic steel after bending process: Martensitic transformation and hydrogen embrittlement analysis

The aim of this work is to study the delayed cracking phenomenon of the unstable austenitic stainless steels (301 grade) deformed by bending operations. During the clamp-forming operation, austenite is transformed to α′α′-martensite. To understand this phenomenon, morphological analysis and hardness measurements were made. Scanning electron microscopy (SEM) was used to perform fracture surface analysis and X-ray diffraction (XRD) to measure the amount of the martensite . The breaking patterns of these clamps obtained after delayed cracking are predominantly intergranular. This type of failure is often associated with hydrogen embrittlement. This brittle behavior is accentuated by the presence of internal stresses in the material (cold rolling, forming by bending) and the high content of martensite.