Microstructural and Mechanical Characterization of Dissimilar Metal Welding of Inconel 625 and AISI 316L

Abstract

This study investigated the microstructure of the dissimilar metal welding of Inconel 625 and AISI 316L using Continuous Current Gas Tungsten Arc Welding (CCGTAW) and Pulsed Current Gas Tungsten Arc Welding (PCGTAW) processes with ERNiCr-3, TIG 316L and twisted (ERNiCr-3 and TIG 316L) fillers. Microstructure examinations were carried out using an optical microscope and Scanning Electron Microscopy (SEM)/Energy Dispersive X-Ray (EDAX). The results of the study showed the existence of a partially melted zone (PMZ) on the AISI 316L side. Weld zone (WZ) analysis showed the existence of a multi-directional grain growth on the 316L side in all specimens, although less growth was found on the Inconel 625 side. Grain growth almost disappeared using PCGTAW with twisted fillers. SEM/EDAX investigations indicated that secondary deleterious secondary phases were tiny and white in five experiments. However, a meager amount of precipitates occurred in PCGTA welding with twisted fillers. Moreover, these were particularly innocent precipitates, represented by black dots in images, whereas other tiny white secondary phases are known to be brittle. As a result, PCGTA welding with twisted fillers exhibited the best metallurgical properties.

Dissimilar Metal Welding

“…This special issue of Metals covers sixteen articles [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] focused on dissimilar metal joining techniques. Some of the published reports have confirmed the increasing interest in solid state welding processes, in particular friction based welding [6][7][8][9][10] and electromagnetic pulse welding [11,12], due to benefits related to the properties and achievable microstructure, and to energy and environmental considerations.…”

“…Some of the published reports have confirmed the increasing interest in solid state welding processes, in particular friction based welding [6][7][8][9][10] and electromagnetic pulse welding [11,12], due to benefits related to the properties and achievable microstructure, and to energy and environmental considerations. Other papers dealt with fusion welding techniques, mainly laser based [13][14][15][16], among others [5,17], and brazing processes [18,19]. Most of the applications are related to the automotive and aerospace sector, nevertheless dissimilar joints, characterized by improved fracture resistance, were indicated as an indispensable part of nuclear power plants for connecting the safe end (austenitic stainless steel 316L) to the pipe-nozzle (ferrite low-alloy steel A508) [20].…”

Mechanical Behavior of Inconel 625 at Elevated Temperatures

“…Between the nickel-based alloys, Inconel 625 one of the most widely used in high-temperature applications, such as in the aerospace, petrochemical, marine, and nuclear industries. This can be attributed to its excellent oxidation resistance and mechanical properties [1][2][3]. This superalloy is strengthened by the solid-solution-hardening effects of alloying elements such as chromium, molybdenum, niobium, and iron, and the precipitation-hardening effects of their intermetallic phases.…”

Functionally Graded SS 316L to Ni-Based Structures Produced by 3D Plasma Metal Deposition

“…In thermal and nuclear plants the joint of Inconel 625 to AISI 304L is used in cryogenic applications [32], in sub-sea manifolds dissimilar joints of Inconel 625 and duplex stainless steel are employed [33], NASA manufactured the sub-scale boilers using dissimilar Inconel 625 to austenitic stainless steel [34]. In addition, the union of Inconel 625 to ASS is used in calcining process involving chromic acid which contains diluted acidic environment [35]. Another typical application of the bimetallic components is the sub-scale boiler employed for Advanced Stirling Conversion System project, where the sub scale boiler was built with AISI 316 for the condenser and Inconel 625 with 304L stainless steel wick for the boiler [36].…”