Unmixed zone formation in austenitic stainless steel weldments. [18 Cr-8 Ni weldments]
An investigation of the weld interface region in heterogeneous austenitic stainless steel weldments on an 18Cr-8Ni base metal indicates that a well-developed unmixed zone exists along the boundary separating the weld composite region from the partially-melted region. Since the unmixed zone exists as a laminar layer of base metal which has melted and resolidified in situ during the welding process, the average composition of this region is identical to that of the base metal. The duplex austenite-ferrite microstructure of the unmixed zone appears similar morphologically to the microstructure of autogenous 18Cr-8Ni weldments. Constant extension rate stress-corrosion cracking tests were performed on transverse-welded tensile specimens in room and elevated temperature chloride-containing solutions which readily produce stress-corrosion cracking in 18Cr-8Ni base materials. Test results indicate that the duplex unmixed zone can be preferentially susceptible to corrosion-induced attack. Preferential environmentally-induced cracking in the unmixed zone of both Type 310/Type 304L and Type 312/Type 304L weldments is particularly severe in low pH, room temperature solutions; it involves the combined and interrelated occurrence of stress-assisted ferrite dissolution and stress-corrosion cracking in the austenite. Designing a wholly austenitic weldment by simply using a high-nickel filler metal is not possible. It could lead to catastrophic results if such weldments are employed under conditions conducive to stress-corrosion cracking.
- OSTI ID:
- 6299345
- Journal Information:
- Weld. J. (Miami); (United States), Journal Name: Weld. J. (Miami); (United States) Vol. 58:6; ISSN WEJUA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360101* -- Metals & Alloys-- Preparation & Fabrication
360105 -- Metals & Alloys-- Corrosion & Erosion
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
ALLOYS
CHEMICAL REACTIONS
CHLORIDES
CHLORINE COMPOUNDS
CHROMIUM ALLOYS
CHROMIUM STEELS
CHROMIUM-NICKEL STEELS
CORROSION
CORROSION RESISTANT ALLOYS
CORROSIVE EFFECTS
CRACKS
CRYSTAL STRUCTURE
FRACTURE PROPERTIES
HALIDES
HALOGEN COMPOUNDS
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
HYDROGEN COMPOUNDS
INORGANIC ACIDS
IRON ALLOYS
IRON BASE ALLOYS
JOINTS
MAGNESIUM CHLORIDES
MAGNESIUM COMPOUNDS
MATERIALS
MECHANICAL PROPERTIES
MICROSTRUCTURE
NICKEL ALLOYS
SODIUM CHLORIDES
SODIUM COMPOUNDS
STAINLESS STEEL-304L
STAINLESS STEEL-310
STAINLESS STEELS
STEELS
STRESS CORROSION
SULFURIC ACID
WELDED JOINTS