Effect of heat treatment on susceptibility of duplex stainless steel to embrittlement by hydrogen

Slow straining of smooth tensile specimens of heat treated duplex stainless steel from a fabricated pipe has been used to assess susceptibility to emb rittlement by hydrogen. The effect of the proportions of ferrite and austen ite in the microstructure, produced by quenching after solution treatment a t temperatures between 1000 and 1300 degrees C, on the ductility was measur ed. Tests were carried out by either straining in a hydrogen atmosphere or in air after thermal charging in high pressure hydrogen. The measured susce ptibility increases proportionately with increase in the amount of ferrite in the structure and reflects the role of austenite in arresting propagatin g cracks. However, there is little doubt that the amount of austenite prese nts greater dominance than its orientation in this respect, MST/4326.