Inhibition of Hydrogen Embrittlement in High Strength Steel.
Abstract
The addition of rare earth gettering agents to trap hydrogen was evaluated as a method of reducing the embrittlement problems in steel cathodically charged with hydrogen. Additions of lanthanum and cerium made to AISI 4340 steel were used in the 0.03-0.17 weight percent range. Mechanical property results were comparable for both elements and indicated that while some degradation in property levels occurred, particularly at the high rare earth content, most of the aircraft quality specification minimums for 4340 high strength steel were attained. An important exception was the charpy impact strength, which was approximately 15% below the minimum. Property loss was attributed to the formation of continuous rare earth oxide inclusions at prior austenite grain boundaries. Delayed failure test results indicated substantial improvements in hydrogen embrittlement resistance for high rare earth content (>0.15 weight percent) steels. This was manifested in terms of increased time to crack initiationn (incubation time), increased failure time, higher values for the lower critical stress intensity and lower crack growth rates compared to baseline 4340 or the low rare earth modifications. Cerium was slightly superior to lanthanum only in terms of resulting in a higher level for the lower critical stress intensity. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1977
- Accession Number
- ADA037355
Entities
People
- C. S. Kortovich