Control of Laves phase in Inconel 718 GTA welds with current pulsing

TLDR

Nb‑rich Laves phase in Inconel 718 welds degrades mechanical properties. The study aimed to control Laves phase formation in Inconel 718 gas tungsten arc welds by using pulsed current. Welds were fabricated on 2 mm sheets with constant or pulsed current, then solution‑treated at 980 °C, aged, and subjected to microstructural analysis and tensile testing at 650 °C. Pulsed current refined the fusion‑zone microstructure, reduced Laves phase quantity and improved its morphology, and enhanced post‑heat‑treatment response and tensile properties.

Abstract

The presence of Nb rich Laves phase in Inconel 718 weld fusion zones is known to be detrimental to weld mechanical properties. In the present study, an attempt was made to control the formation of Laves phase in alloy 718 gas tungsten arc welds using pulsed current. Welds were produced in 2 mm thick sheets of the alloy with constant current and pulsed current and were subjected to post-weld solution treatment at 980°C followed by aging. Detailed microstructural studies and tensile tests at 650°C were conducted. The results show that the use of current pulsing (i) refines the fusion zone microstructure, (ii) reduces the amount of Laves phase and exerts a favourable influence on its morphology and (iii) improves the response of the fusion zone to post-weld heat treatment and weld tensile properties.