Hydrogen embrittlement of a Ti-strengthened 250 grade maraging steel

Abstract

Constant extension-rate tensile tests are performed to investigate the effects of strain rate and environmental hydrogen concentration on the tensile properties of various aged T-250 specimens, The 426 degrees C (800 degrees F) underaged specimens are very sensitive to strain rate; the 482 degrees C (900 degrees F) peak-aged specimens exhibit a reduced ductility under low strain rates; and the 593 degrees C (1100 degrees F) overaged specimens are insensitive to strain rate when tested in air, The excellent resistance to embrittlement of the overaged specimens in gaseous hydrogen could be associated with the extensive formation of reverted austenite and the incoherent Ni3Ti precipitates, The tensile-fractured surfaces of such specimens reveal a ductile dimple fracture, However, the peak-aged specimens are susceptible to gaseous hydrogen embrittlement, and the embrittled region shows a primary fracture mode of quasi-cleavage, The least resistant to hydrogen embrittlement of the underaged specimens is characterized by a more brittle fracture appearance, that is, intergranular fracture, under a low strain rate or in the gaseous hydrogen environment.