The control of catalytic poisoning and stress corrosion cracking

✍ Scribed by H.W. Liu; Hu Ya-Lung; P.J. Ficalora

• Publisher: Elsevier Science
• Year: 1973
• Tongue: English
• Weight: 786 KB
• Volume: 5
• Category: Article
• ISSN: 0013-7944
• DOI: 10.1016/0013-7944(73)90023-4

✦ Synopsis

Aktrcld-When a structti metal is stressed in a hydrogen environment, the metal may crack at st.mss levd~ much lower than its normal stmngth. This embrittlement is caused by hydrugen atoms or ions rather than hydrogen mdecoles. The catalytic dissociation of hydrogen molecules into atoms or ions takes place at diaocation~sonametals~.Thetenniniofdislocationsonametalsurfacerrrsitesoflocalwd~ eneqgy. there arc "poi8on8" which will retard or even stop catalytic processes. The toxicity of a poison depends on the binding energy of the foreign atom to a dislocation terminus. Cracked specimens made of 4340 steel were tested in hydrogen gas and its mixture with SO*, C&, CO*, NI and &. Roth SO, and CS, are very "'toxic" and can stop a ronning crack. The toxicity of CO, is moderate. Nt and Ar have no noticeable effect on a running crack.