Heat treatment effects on Inconel 625 components fabricated by wire + arc additively manufacturing (WAAM)—part 2: mechanical properties

This study investigates the mechanical properties of the wire + arc additively manufactured Inconel 625 thin wall. The first part of this study focused on the microstructural features of the material after time-based annealing. This second part discusses the tensile strength and microhardness of the material after the same annealing procedure (980 °C, hold time 30 min, 1 h, and 2 h). It is found that the annealing procedure improved the ultimate tensile strength by 5%. Although the yield strength remains unchanged up to 1-h of annealing, it increases after 2-h of heat treatment. The presence of strengthening elements and precipitation of secondary phases seem to control the tensile strength of the additively manufactured Inconel 625. On the other hand, the average microhardness does not show any significant trend for time-based heat treatment. However, the layer-specific variation of microhardness was observed in the sample, which may have caused high standard deviation in the as-deposited sample. Overall, the annealing procedure with a 2-h hold time presents the best mechanical properties of the Inconel 625 so far. Nevertheless, further improvement in strength and hardness may require a comprehensive study with location-specific microstructure and mechanical properties analysis before and after the heat treatment procedure.