Accession Number : ADA288447

Title :   Evaluation of a Diffusion/Trapping Model for Hydrogen Ingress in High-Strength Alloys.

Descriptive Note : Annual rept. 15 Sep 93-14 Sep 94,

Corporate Author : SRI INTERNATIONAL MENLO PARK CA

Personal Author(s) : Pound, Bruce G.

PDF Url : ADA288447

Report Date : NOV 1994

Pagination or Media Count : 69

Abstract : The ingress of hydrogen in various high-strength alloys was investigated with a view to characterizing their susceptibility to hydrogen embrittlement (HE). A potentiostatic pulse technique was applied to two precipitation-hardened iron-base alloys (AerMet 100 and alloy A-286), two Cu-containing alloys (Be-Cu and alloy K-500), and a superferritic stainless steel (UNS 544660) in 1 mol/L acetic acid-1 mol/L sodium acetate. The data were analyzed using a diffusion/trapping model to obtain the irreversible trapping constant (k) and hydrogen entry flux for each alloy. Irreversible trapping was negligible in overaged AerMet 100 but pronounced in the aged alloy. The order of the k values for AerMet 100 and two steels (4340 and 1 18Ni) previously studied inversely parallels their threshold stress intensities for stress corrosion cracking. Likewise, the k values of alloy A-286, 18Ni steel, and also alloy 718 from earlier work are consistent with test data for their relative resistance to HE. The results for AerMet 100 and alloy A-286 extend the previously reported correlation between k and HE resistance. Unaged Be-Cu is intrinsically more susceptible to HE than unaged alloy K- 500. The type of heat treatment has a marked effect on the rapping behavior of alloy K-500. The intrinsic susceptibility of the annealed and aged alloy is twice that or the direct-aged alloy. The propensity of the S44660 alloy to undergo HE at cathodic protection potentials can be attributed to the absence of an oxide and hence the relatively unrestricted entry of H.

Descriptors :   *HIGH STRENGTH ALLOYS, *IRON ALLOYS, *HYDROGEN EMBRITTLEMENT, EXPERIMENTAL DATA, CRACKS, COPPER ALLOYS, STAINLESS STEEL, CARBIDES, HEAT TREATMENT, CORROSION RESISTANCE, CATHODIC PROTECTION, AGE HARDENING, POTENTIOSTATIC TECHNIQUES, STRESS CORROSION, NICKEL STEELS, YIELD STRENGTH, OXIDATION RESISTANCE.

Subject Categories : Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE