Effect of Mn Content on Microstructure and Properties of Inconel718 Plate Welded Joint

Abstract

The service performance of welded parts is directly impacted by the microstructure of the Inconel 718 welded joint； however， there is a lack of comprehensive research on the impact of the Mn element on the microstructure and perfor⁃ mance of the welded junction. In this study， the solid-solution Inconel 718 hot-rolled plates with varied Mn concentrations of <0. 01%，0. 24%， and 0. 34% were joined by using DC pulse arc welding before two stages of thermal aging. The ten⁃ sile test of these plates was performed at room temperature to determine the impact of Mn content on the microstructure and aging mechanical properties of welded joints. The results demonstrate that there are only the Laves phase and no δ phase in the welded joints with three different Mn concentrations. The volume proportion of Laves phase precipitates in the welded joints significantly increases as the Mn content rises from ＜0. 01% to 0. 34%. However， the content of Laves phases decreases slightly， and γ΄΄ begins to precipitate after a two-stage thermal aging treatment. In addition， the tensile strength and elongation of the welded joint are inferior to those of the aged base metal. The tensile properties of the aged welded joints are worsened by the increase in Mn content， causing a decrease in tensile strength from 1 250 MPa to 1 178 MPa and 1 213 MPa， respectively. The three welded joints are broken at the welded areas in the tensile test， all of which are ductile fractures.

Keywords

• inconel718 alloy； mn content； laves phase； welding performance