Evaluation of a Diffusion/Trapping Model for Hydrogen Ingress in High-Strength Alloys.
Annual Technical rept. 15 Mar 86-15 Mar 87,
SRI INTERNATIONAL MENLO PARK CA
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This report covers work performed during the first year of a program to apply a diffusiontrapping model for hydrogen ingress in three high-strength alloys, AISI 4340 steel, Monel K500, and MP35N. The model is coupled to the use of a potentiostatic double-pulse technique, and current transient data were obtained for the alloys in 1 M HAc1 M NaAc Ac acetate with 15 ppm AS2O3. In all cases, the anodic charge can be analyzed as a function of charging time in terms of an interfacial control model in which the rate of H ingress into the metal is determined by the flux across the metal surface. The 4340 steel was tested at yield strengths of approximately 175 and 250 ksi. The rate constant for irreversible trapping, k, was evaluated from the measured or apparent rate constant, ka, by estimating the effect of reversible traps from diffusivity data and was found to be 4s for both 4340 specimens. Keywords Steel Monel Hydrogen Ingress Models Diffusion Trappping High strength Alloys Hydrogen embrittlement.
- Metallurgy and Metallography