Abstract
The nature and kinetics of the δ-ferrite transformation in a series of duplex submerged arc 316 L weld metals has been studied under creep conditions at 600° C and an applied stress of 200 MN m−2. The δ-ferrite was found to transform first to M23C6 carbides, these occurring at either the δ/γ interface or within the δ-ferrite laths depending upon the presence of suitable nucleation sites. The remaining δ-ferrite then transforms to the intermetallic σ-phase. The kinetics of the intermetallic phase formation varied between the different welds, and STEM/EDAX analysis indicated that the kinetics were dependent on the localized segregations of chromium, nickel and molybdenum in the δ-ferrite laths. A transformation model has been developed which indicates that chromium diffusion within the γ matrix is the controlling mechanism.
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Farrar, R.A., Thomas, R.G. The microstructure and phase transformations in duplex 316L submerged arc weld metals. J Mater Sci 18, 3461–3474 (1983). https://doi.org/10.1007/BF00544175
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DOI: https://doi.org/10.1007/BF00544175