THE EFFECT OF THE PRESENCE OF UNTEMPERED MARTENSITE ON STRESS CORROSION PROPERTIES OF AISI 410
AISI 410 specimens tempered over 1125 deg F for 4 hr minimum. supposedly immune to stress corrosion cracking. showed anomalous stress corrosion results after 1 week exposure in 300 deg F air saturated water with applied stress of 60,000 psi. The unexpected stress corrosion failures were attributed to an improper heat treating practice. The specimens were not fully cooled, from the austenitizing temperature, to below M/sub f/ before tempering, thus retaining untransformed austenite. The retained austenite converted to untempered martensite on cooling from the tempering temperature. The studies revealed that initiation and propagation of the stress corrosion cracks were promoted by and directly proportional to the amount of untempered martensite present. Proper heat-treat procedures (cooling from austenizing temperature to room temperature to allow complete conversion of austenite to untempered martensite prior to exposure for 4 hr minimum to tempering temperatures in excess of 1125 deg F) will make the alloy immune to stress corrosion failures. At present. metallographic studies are the best and only available method to inspect for proper (absence of untempered martensite) heat treating practices. A second temper at 1125 deg F or higher (double tempering) will convert any untempered martensite to tempered martensite. This double tempering procedure will have to be evaluated to determine that metallurgical changes, especially the bands of isothermal transformation products formed in the prior austenite grain boundary, do not have any significant effects on the mechanical and corrosion properties. (auth)
- Research Organization:
- Knolls Atomic Power Lab., Schenectady, N.Y.
- NSA Number:
- NSA-15-007706
- OSTI ID:
- 4112215
- Report Number(s):
- KAPL-M-HOS-11
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-61
- Country of Publication:
- United States
- Language:
- English
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