Microstructure and Mechanical Properties of Friction-Welded Alloy 718 and SNCRW Stainless Steel After Post-Weld Heat-Treatment

Abstract

This study investigated dissimilar friction welding of Alloy 718 to SNCRW stainless steel. After friction welding, the effect of post-weld heat-treatment (PWHT) on the microstructure and mechanical properties was carefully studied. For this purpose, friction welded samples were annealed at 500, 720, and 900 ℃ for 8 hrs, respectively. Heat-treatment at 720 ℃ resulted in highest hardness due to the precipitation of g". On the other hand, relatively low hardness was obtained when PWHT was not performed, or the heat-treatment temperature was not 720 ℃. Residual stress in the welded joints was effectively reduced when heat treatment was performed at temperatures above 720 ℃. Friction welded specimens fractured at the weld joint when no PWHT was performed or when PWHT was performed at 500 or 900 ℃. On the other hand, when PWHT was performed at 720 ℃, tensile failure occurred in the SNCRW base metal.

Evaluation of the mechanical properties of Inconel 718 to SCM 440 dissimilar friction welding through real-time monitoring of the acoustic emission system

“…Materials with less strength and hardness tend to plastically deform under the dynamic force and high temperature during friction welding. 27–31 Figures 8(b) and 6(c) indicate the microstructures of the weld flash which is formed during welding on the IN718 side and on the SCM440 side, respectively. As can be seen from the macrostructures, the weld flash on the IN718 side is not noticeable compared to the SCM440 side.…”