Influence of Microstructure and Mechanical Properties of Dissimilar Rotary Friction Welded Inconel to Stainless Steel Joints

Abstract

The present study aims to evaluate the microstructure, grain size, and mechanical properties of the dissimilar AISI 316L/Inconel 718 (IN 718) rotary friction welded joints under both the as-welded and post-weld heat treatment (PWHT) conditions. Because of reduced flow strength at elevated temperatures, the AISI 316L and IN 718 dissimilar weldments exhibited more flash formation on the AISI 316L side. At higher rotating speeds during friction welding, an intermixing zone was created at the weld joint interface due to the material softening and squeezing. The dissimilar welds exhibited distinctive regions, including the fully deformed zone (FDZ), heat-affected zone (HAZ), thermo-mechanically affected zone (TMAZ), and the base metal (BM), located on either side of the weld interface. The dissimilar friction welds, AISI 316L/IN 718 ST and AISI 316L/IN 718 STA, exhibited yield strength (YS) of 634 ± 9 MPa and 602 ± 3 MPa, ultimate tensile strength (UTS) of 728 ± 7 MPa and 697± 2 MPa, and % elongation (% El) of 14 ± 1.5 and 17 ± 0.9, respectively. Among the welded samples, PWHT samples exhibited high strength (YS = 730 ± 2 MPa, UTS = 828 ± 5 MPa, % El = 9 ± 1.2), and this may be attributed to the formation of precipitates. Dissimilar PWHT friction weld samples resulted in the highest hardness among all the conditions in the FDZ due to the formation of precipitates. On the AISI 316L side, prolonged exposure to high temperatures during PWHT resulted in grain growth and decreased hardness. During the tensile test at ambient temperature, both the as-welded and PWHT friction weld joints failed in the HAZ regions of the AISI 316L side.

Microstructure and Mechanical Properties of IN690 Ni-Based Alloy/316LN Stainless-Steel Dissimilar Ring Joint Welded by Inertia Friction Welding

“…It was discovered that the tensile fracture was on the AISI 304 side, and a network of dimples was present on the fractured surface. Beeravolu et al [22] investigated the effect of CDFW on the microstructure and mechanical properties of joints between IN718 and AISI 316L in both post-weld heat treatment (PWHT) and as-welded conditions. It was discovered that under both as-welded and PWHT conditions, the tensile fracture happened in the HAZ on the AISI 316L side.…”