Role of rare-earth yttrium in the hydrogen embrittlement of AISI 321 austenitic stainless steel

Abstract

The hydrogen embrittlement of AISI 321 austenitic stainless steel without and with 0.045 wt% rare-earth yttrium was studied with slow strain rate test, X-ray diffraction, scanning electron microscopy, electron back scattered diffraction, and transmission electron microscopy. The results indicate that rare-earth microalloyed AISI 321 austenitic stainless steels show better ductility in a hydrogen environment, where the plastic loss of a specimen with 0.045 wt% yttrium is 25.27 ± 3.74%, which is significantly lower than that of a specimen without yttrium (35.02 ± 1.95%). There are two important roles of rare earth yttrium in hydrogen embrittlement of AISI 321 austenitic stainless steels. The first is that rare-earth yttrium tends to interact with titanium and improves the stress concentration around Ti(C, N) by reducing its size and increasing its number. In addition, rare-earth yttrium contributes to reducing the inclination of stress and hydrogen-induced martensitic phase transformation in metastable AISI 321 stainless steel. This work is valuable for improving resistance of austenitic stainless steel to hydrogen embrittlement.