Cleavage fracture of austenite induced by nitrogen supersaturation

The association of nitrogen content of different saturation levels in austenitic stainless steels with their brittleness at different temperatures was investigated. Fe-Cr-Mn-N austenitic stainless steel (P900) was elaborated with the pressurized electro slag remelting. The two low nitrogen steels us...

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Bibliographic Details
Published in:Scripta metallurgica et materialia 1994-09, Vol.31 (5), p.549-554
Main Authors: Vogt, J-B, Messai, A, Foct, J
Format: Article
Language:English
Subjects:
360103 - Metals & Alloys- Mechanical Properties
ALLOYS
AUSTENITIC STEELS
BRITTLENESS
DATA
DUCTILE-BRITTLE TRANSITIONS
ELEMENTS
EXPERIMENTAL DATA
FRACTURE PROPERTIES
HIGH ALLOY STEELS
INFORMATION
IRON ALLOYS
IRON BASE ALLOYS
MATERIALS SCIENCE
MECHANICAL PROPERTIES
METALLURGICAL EFFECTS
NITROGEN
NITROGEN ADDITIONS
NONMETALS
NUMERICAL DATA
STAINLESS STEELS
STEELS
YIELD STRENGTH
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Summary:The association of nitrogen content of different saturation levels in austenitic stainless steels with their brittleness at different temperatures was investigated. Fe-Cr-Mn-N austenitic stainless steel (P900) was elaborated with the pressurized electro slag remelting. The two low nitrogen steels used were 17Cr-12Ni-2.5Mo-0.03N (AISI 316L) and 17Cr-12Ni-2.5Mo-0.25N (AISI 316LN). Impact strength, plastic flow stress, cleavage stress, yield stress, and effective stress were studied. P900 showed a high impact strength at 300K and 223K, but it declined sharply at lower temperatures. On the other hand, both AISI 316L and 316LN showed high impact strength in all temperatures between 77K and 300K. Completely ductile fracture was evident from the SEM images of fracture surfaces of P900 at 223K, with dimples all over the surface. Lattice parameter increased in P900 with increasing localization of deformation. Brittle fracture was found to occur both intergranularly and transgranularly. Cleavage was associated with marked slip. Brittle rupture stress and flow stress for P900 varied in opposite directions with variation in nitrogen content. This defines the occurence of brittle to ductile transition. Observations indicate that higher nitrogen content affects mainly the effective stress.
ISSN:0956-716X
DOI:10.1016/0956-716X(94)90142-2