Effect of Post-weld Heat-Treatment on Microstructure and Mechanical Behavior of Inconel 625 Overlay Cladding on 2.25 Cr-1Mo Steel

The influence of post-weld heat-treatment (PWHT) temperatures at 690 °C with a 1-h hold time on the microstructure and mechanical characteristics of Inconel 625 overlay cladding on a 2.25 Cr-1Mo steel were studied. Welded Inconel 625 overlay shows a distinct grain structure and size variation. After post-weld heat treatment, weld metal had slightly increased in hardness due to the dendrite austenite phase from as-welded was transformed to the austenite phase (γ) and the crystallization of the metal compound (γ′) in the matrix. Heat-affected zone after PWHT consisted of tempered bainite which improved the toughness, but the average hardness was reduced from 275.7 ± 7.9 HV0.2 to 231.0 ± 4.5 HV0.2. The results from the Charpy impact test show that the welding metal area of the PWHT sample absorbs more energy than the as-welded sample even at − 40 °C; PWHT provides energy absorption values as high as 160 J (as-welded value 63 J) and still shows ductile failure behavior.