Enhancement of tensile properties of gas tungsten arc welds using Cu-coated CoCrFeMnNi filler and post–weld heat treatment

Abstract

This study investigated the gas tungsten arc (GTA) weldability of cold-rolled CoCrFeMnNi high-entropy alloys (HEAs) using Cu-coated HEA filler, specifically through the application of various post–weld heat treatment (PWHT) temperatures. The GTA weldability of cold-rolled HEA was evaluated by applying the optimum condition of full penetration, and the effect of PWHT was investigated in the temperature range of 973–1173 K. No macro-defects were detected in the weld metal (WM) to which the Cu coated HEA filler was applied. All the PWHT-applied specimens, including the as-welded specimens, were composed of the FCC phase. The Cu component was solid-solutionized over the entire area of the WM and did not form a precipitate. The tensile properties of the as-welded specimens deteriorated in the presence of CrMn oxides. As the PWHT temperature increased, the grain size in the base metal (BM) increased and inclusions in the WM were re-dissolved. Furthermore, by increasing the PWHT temperature, the hardness of the BM decreased significantly by grain growth, and the WM softened slightly owing to the re-dissolution of inclusions. Therefore, the WMs improved the tensile strength and elongation with increasing PWHT temperature. The application of PWHT significantly improved the weldability of the Cu coated CoCrFeMnNi welds.

Keywords

• High-entropy alloys
• Cu component
• Post–weld heat treatment
• GTA weldability
• Microstructure
• Mechanical properties