Alleviating segregation and enhancing tensile properties of Inconel 718 superalloy by twin-roll casting and two-stage cold rolling

Abstract

A novel processing route involving twin-roll casting and two-stage cold rolling was proposed to manufacture Inconel 718 alloy. Due to the sub-rapid solidification rate (412.5 °C/s) of as-cast strip, the element segregation can be alleviated and the growth of Laves phase was effectively suppressed. It was also observed that the dissolution of Laves phases during subsequent homogenization was significantly accelerated because of their refined size. The corresponding homogenization time can be shortened from dozens of hours to 1 h. Additionally, the non-uniform microstructure of cold-rolled and annealed samples caused by coarse grains from homogenization treatment can be eliminated by two-stage cold rolling method. Furthermore, a large amount of granular δ phases precipitated during intermediate annealing. After double aging treatment, the final products exhibited an excellent combination of strength and elongation. The ultimate tensile strength when deformed at room temperature and at 650 °C were about 1475 and 1120 MPa, and the corresponding total elongation were ∼ 15% and ∼ 22%. These results indicated that the twin-roll casting was a promising route to produce Inconel 718 alloy.