[ materials ]
Fig . 6 . Fracture surface of EN 1.4404 : left − cathodic charging , middle − thermal pre-charging , right − testing at 87.5 MPa at −40 ° C
Fig . 7a . UNS S21900 Fig . 7b . UNS S31675 ( red areas are inclusions )
Fig . 7c . EN 1.4435 Fig . 7d . EN 1.4404
gas results in a pass for all four materials ( see Table 4 ), even though the low-nickel version of UNS S31603 , EN 1.4404 , has a low ratio for the reduction of area and a brittle fracture surface . For the other three materials , ductile fractures were observed in the high-pressure hydrogen gas , indicating good resistance to hydrogen embrittlement . This also applies to the coldworked UNS S21900 . It should be noted that SAE J2579 stipulates that the nickel content shall be above 13 % for austenitic stainless steels .
It is not only nickel that is an austenitestabilizing element ; both N and Mn are strong austenite-stabilizing elements as well . All the
46 Hydrogen Tech World | Issue 17 | August 2024