SEDL / STP / STP962-EB / STP45301S

A Bent Beam Test Method for Hydrogen Sulfide Stress Corrosion Cracking Resistance

Cox, Donald O.
Principal engineer, Failure Analysis Associates, Los Angeles, CA

Pages: 10    Published: Jan 1988

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Abstract

Brittle fracture due to hydrogen sulfide exposure of high-strength, low-alloy steel has been recognized for many years. A relatively simple testing procedure used to estimate and rank a material's resistance to hydrogen sulfide stress corrosion cracking is described. This test gives quantitative data regarding relative susceptibility after a relatively short testing period. Field testing is also possible.

Development of the testing procedure is reviewed. The test uses the concept of a “threshold stress,” which is established on a statistical basis for each material or environment under consideration. Results are presented where the test procedure has been used to establish behavior of Grade 9Q thick wall castings [ASTM Specification for Steel Castings Suitable for Pressure Service (A 487/A 487M-84)] fabricated using argon-oxygen deoxidation (AOD) and air-melted materials having niobium and/or molybdenum additions.

One disadvantage of the method is the fact that the test procedure has never been truly standardized. It is hoped that this paper will generate interest in the bent beam method and lead to the development of a standard testing procedure.