Structural Integrity Assessment of Inconel 617/P92 Steel Dissimilar Welds Produced Using the Shielded Metal Arc Welding Process

Interdiffusion Studies in Alloy 617 and 10Cr Steel Joints Using Diffusion Couple Approach and Simulations

“…Yield strength, ultimate tensile strength and elongation (in %) of base materials are (506 MPa, 759, 23) and (367 MPa, 775, 85) for 10Cr steel and alloy 617, respectively. [21] Starting materials for making the diffusion couples were in the form of discs of 10 mm diameter and 3 mm thickness. Flat surfaces of the discs were ground and polished following standard metallographic procedures to achieve a uniform surface roughness of ± 1 lm.…”

“…Considering the compositional dependency of Q and D 0 , good comparison could be made with literature data. [55][56][57] In Fe-(54-73)Ni- (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)Cr (at%) alloys, (Q, D 0 ) values for Cr and Fe are reported as ((282-297) ± 15 kJ/mol, (2-7) 9 10 -4 m 2 /s) and ((275-315) ± 15 kJ/mol, ((0.5-19.9) 9 10 -4 m 2 /s), respectively, in the temperature range of 740-990 °C. [57] Cr diffusion parameters in Inconel alloys vary in the range of 259-276 kJ/mol for Q and (1-2.8) 9 10 -4 m 2 /s for D 0 .…”

“…[17,18] Important observations based on these studies are: (a) formation of a 'transition' region in the weld zone of Shielded Metal Arc Welded (SMAW) 12Cr steel/ENiCrFe [11] and GTAW 12Cr/alloy 617 [12] DMJ (b) enhanced Ni and Cr concentration resulting in c-austenite formation during Post Weld Heat Treatment (PWHT) and c ? a 0 transformation during cooling in SMAW welded P92/alloy 82 or 182 [13] and 16CrMo/alloy 625 Cold Metal Transfer (CMT) joints [14] (c) partial and localized c transformation during creep tests in GTAW alloy 617B/COSTE graded transition joints [19] (d) d-ferrite formation at the interface of GTAW and SMAW P92 weldments [20,21] (e) formation of partially melted/unmixed zones containing Ni deficient and rich ferrite and martensite phases, respectively, at the interface of NG-GTAW alloy 617/high Cr steel [15] and alloy 617B/ COSTE [22] welds and Fe rich FCC phase in the weld metal of laser welded alloy 617/9Cr [23] (f) formation of fine M 23 C 6 carbides in aged alloy 617 which prevents migration of grain boundaries in NG-GTAW alloy 625/9Cr [16] (g) formation of lamellar carbides in the HAZ of alloy 617 that lead to intergranular fracture in NG-SAW alloy 617/9Cr [17] (h) diffusion of carbon and nitrogen across NG-GTAW alloy 617/10Cr interface resulting in the precipitation of M 23 C 6 , M 6 C, AlN and TiN along the grain boundaries leading to cavity formation and creep failure [18] and (i) soft zone formation in GTAW alloy 617/P92 weldments due to carbon transport after PWHT. [20] Thus fusion welded joints exhibit a wide variety of microstructures which transform during PWHT or testing.…”