Weldability of cast CoCrFeMnNi high-entropy alloys using various filler metals for cryogenic applications

Abstract

This study investigates the effect of stainless steel (STS) 308 L and high-entropy alloy (HEA) filler metals on gas tungsten arc (GTA) welding. The weldability of the cast CoCrFeMnNi HEAs was determined based on the microstructural and mechanical properties of the welds. The cast HEA exhibited larger dendrite packets than the weld metals (WMs). The hardness in the WM was superior compared with that in the base metal (BM). The WM using STS 308 L exhibited a fully face-centred cubic (FCC) structure with no indication of 8-ferrite and lower hardness than that using HEA filler. The GTA welds using both fillers showed tensile properties comparable to the cast BM at 298 K, and the tensile fracture of the transverse welds occurred near the cast BM. The cryogenic tensile properties in the GTA welds were superior compared with the room-temperature property due to the significant formation of deformation twins and high dislocation density at 77 K. This was probably due to the decrease in the stacking fault energy at the cryogenic temperature compared with that at the room temperature. Therefore, it is possible to apply commercial STS 308 L filler metal for the CoCrFeMnNi HEA in cryogenic applications. (C) 2019 Elsevier B.V. All rights reserved.