OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) · 1982 · 65 citations · 2 references
EngineeringMaterials EngineeringMaterials ScienceMechanical Behavior Of MaterialsMetallic MaterialsMetallurgyAlloysJoining Of Dissimilar MaterialsStainless SteelsSteel MaterialsWeldingWelding ProcessesFailure Mode AssessmentFailure Mode InvestigationFerritic Stainless SteelsFerritic SteelsInterface MicrostructureJoint ReliabilityMicrostructureWelded Joints
The study investigated the causes of failures in dissimilar austenitic–ferritic weld joints used in superheater and reheater tubes of fossil‑fired steam plants. The authors examined the complex microstructure at the weld–2 1/4 Cr‑1 Mo steel interface in as‑welded, as‑welded‑and‑tempered, and long‑service (over 100 000 h) joints, combining metallographic observations with literature to explain the interface microstructure and failure mode. Cracks were found to initiate and propagate within 5–15 μm of the fusion line in the ferritic steel, and the proposed failure model led to recommendations for improving joint reliability.
The cause of failures of dissimilar-alloy (austenitic or ferritic) joints in superheater and reheater tubes of fossil-fired steam plants was investigated. In the failures of interest, cracks form and propagate in the ferritic steel (usually 2 1/4 Cr-1 Mo steel) about 5 to 15 ..mu..m from the fusion lines. The complex microstructure developed at the interface between weld metal and 2 1/4 Cr-1 Mo steel during welding and elevated-temperature service was examined in (1) the as-welded and as-welded-and-tempered conditions, and (2) failed and unfailed joints having more than 100,000 h of service in a fossil-fired boiler. Metallographic observations on failed and unfailed joints were combined with literature observations to explain the interface microstructure and subsequent failure mode. On the basis of the proposed failure model, recommendations are presented for improving joint reliability.
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