Niobium (Nb) stabilised austenitic stainless steel conforming to SA 213 347 H grade was studied. Material of SA 213 347H grade has a propensity to form TOPOLOGICALLY CLOSE PACKED (TCP) PHASES in particular the sigma phase in the presence of Gr. Va and Gr. VIA elements. TCP phases are considered highly detrimental in the services and leads to proemature expensive catastrophic failures. Specification ASTM 213 in respect of the material 347H may need to specify contents of residual elements in order to save the steel from failing in service prematurely.
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