New Method for Estimating of Radius and Density of Bubbles in Hydrogen Attacked Steel

Abstract

Density Synopsis Analytical equations to estimate the density and radius of bubbles formed during the incubation period of hydrogen attack in a 2.25Cr-1Mo steel were proposed, and the experiment to verify the validity of the equations was carried out. The hydrogen dif fusivity and the density change in the steel are correlated with the bubble density, ps and the bubble radius, r, as LAKE P~ =-4 z 72n4r3-P P d p-34r(_ P r= K B where, d p/p : the density change caused by bubbles dr: the thickness of shell around each bubble which acts as the trapping site of hydrogen atoms kB: the total volume of all shells LA: the mean intercept of prior austenite grains. The hydrogen diffusivity and the density change were measured for the quenched and tempered steel which was exposed to elevated temperatures in a high pressure hydrogen atmosphere. These measured values were substituted into the above equations to give values of p~ and r in good agreement with the structural observation.