FRACTURE-MECHANICAL BEHAVIOR OF THE STEEL-15-MNNI-6-3 IN ARGON AND INHIGH-PRESSURE HYDROGEN GAS WITH ADMIXTURES OF OXYGEN

For the low alloyed fine grained ferritic structural steel 15 MnNi 6 3 in a first step J-integral tests were performed at room temperature i n argon, pure high pressure hydrogen gas as well as with admixtures of oxygen (10 vpm, 150 vpm) in the single specimen technique. The J(R)-c urve received for pure hydrogen environment is essentially lower than the curve for argon. The J(R)-curve for hydrogen with 10 vpm oxygen is shifted towards the one for pure hydrogen whereas the admixture of 15 0 vpm oxygen results in a J(R)-curve near the argon curve. The J(Ic)-v alue for 10 vpm oxygen admixture is approximately twice the one for pu re hydrogen, for 150 vpm oxygen admixture about three times that for p ure hydrogen. For the specimen fractured in argon a dimpled fracture s urface, for the one tested in pure hydrogen a flat quasi-cleavage frac ture was observed. With increasing oxygen admixture the portion of duc tile fracture grows. (C) 1998 International Association for Hydrogen E nergy.