The effects of the heat treatment on the microstructure of Inconel 625/steel bimetal joint obtained by explosive welding

Abstract

In this investigation steel P355NH was successfully clad with Inconel 625 through the method of explosive welding. Explosively welded bimetal was subjected to the two separated heat treatment processes: stress relief annealing (at 620oC for 90 minutes) and normalizing (at 910oC for 30 minutes). In order to identify the microstructure of the joint and to investigate the influence of the heat treatment on it, the light and scanning electron microscope observations and microhardness analysis have been performed. In order to investigate the diffusion zone microstructure the scanning transmission electron microscope observation have been performed. It was stated that obtained joint has characteristic wavy-shape geometry with the presence of the melted zones and severe deformed grains of both joined materials. Strengthening of materials in joint zone was established with microhardness analysis. In both of the heat treatments the changes in the grain structure have been observed. The normalizing heat treatment has the most significant impact on the microstructure of the joint as well as the concentration of the chemical elements in the joint zone. It was reported that due to normalizing the diffusion zone has been formed together with precipitates in the joint zone.