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Plastic ? factor is adopted to account for crack tip plasticity while evaluating the fracture toughness of the materials as per ASTM E1820. It is valid only for homogeneous materials. The plastic ? factor for Compact Type (C(T)) geometry with type 316LN stainless steel weld has been evaluated based on elastic-plastic FE analysis. The incremental elastic-plastic material model with various values for strength mismatch ratio (M) i.e. ratio of yield strength of weld metal to that of base metal, from 1.2 to 2.2 have been considered. The weld width (h) parallel to the crack plane is varied from 4 mm to 16 mm. The ? values thus obtained are analyzed and the inferences are discussed.

Modified 9Cr-1Mo ferritic steel is a preferred material for steam generators in nuclear power plants for their creep strength and good corrosion resistance. Austenitic stainless steels, such as type 316LN, are used in the high temperature segments such as reactor pressure vessels and primary piping systems. So, the dissimilar joints between these materials are inevitable. In this investigation, dissimilar joints were fabricated by the Shielded Metal Arc Welding (SMAW) process with Inconel 82/182 filler metals. The notch tensile properties and Charpy V-notch impact toughness properties of various regions of dissimilar metal weld joints (DMWJs) were evaluated as per the standards. The microhardness distribution across the DMWJs was recorded. Microstructural features of different regions were characterized by optical and scanning electron microscopy. Inhomogeneous notch tensile properties were observed across the DMWJs. Impact toughness values of various regions of the DMWJs were slightly higher than the prescribed value. Formation of a carbon-enriched hard zone at the interface between the ferritic steel and the buttering material enhanced the notch tensile properties of the heat-affected-zone (HAZ) of P91. The complex microstructure developed at the interfaces of the DMWJs was the reason for inhomogeneous mechanical properties.