Abstract
J integral measurements have been conducted on various samples of 304L stainless steel having different levels of austenite stability as a result of variations in composition. In certain materials, significant deviations from the theoretical blunting line (∆a=J/2σf, where ∆a is the effective crack length for a particular J integral and σf is the mean of the 0·2% proof stress and the ultimate tensile strength) were shown in the experimental results. These deviations are discussed and a method is proposed for rationalising the results to allow a more meaningful assessment to be made of the effects of hydrogen charging on the various materials. In this way, a significant reduction in the value of JIc is clearly revealed in materials in which martensite may be produced by deformation. Hydrogen charging also produces a significant decrease in the slope of the experimental blunting line for these materials that is not consistent with the observed increase in proof stress. It is suggested that this decrease is associated with the localisation of plastic deformation by the presence of hydrogen.
MST/775
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