The effect of aging on hydrogen trapping in ß-titanium alloys

Abstract

The ingress of hydrogen in three ß-titanium alloys (Beta-C, Ti10V2Fe3Al, and Ti13V11Cr3Al) and an α-ß titanium alloy (Ti6Al4V) was investigated with a view to characterizing their interaction with hydrogen. A technique referred to as hydrogen ingress analysis by potentiostatic pulsing (HIAPP) was used to obtain anodic current transients for the unaged and aged ß-Ti alloys and as-received Ti-6-4 in an acetate buffer (1 mol L −1 HAc/l mol L −1 NaAc, where Ac = acetate). The transients were analyzed using a diffusion/trapping model under interface control conditions to evaluate the trapping constants and hydrogen entry flux in each case. A marked increase in irreversible trapping was observed for the ß-titanium alloys with aging and was attributed to precipitation of secondary α phase. Aging also induced changes in the passive film and hence the hydrogen entry flux. Ti-13-11-3 and Ti-10-2-3 are predicted to become less resistant to hydrogen embrittlement with aging as a result of increases in both the trapping constant (at least for Ti-13-11-3) and the flux. In contrast, the change in resistance of Beta-C Ti with aging is subject to the opposing effects of a reduced flux and an enhanced trapping capability, though the latter appears to have the primary effect, rendering aged Beta-C Ti less resistant to hydrogen embrittlement than the unaged alloy.