Influences of γ and δ precipitations on the microstructural properties of 718 alloy through HIP, solid-solution, and different aging heat treatments

Abstract

In our previous work, the parameters of solid-solution treatment for 718 alloy were discussed. The results showed that a solution temperature of 1020°C is optimum. The Laves and S phase can complete solution after 1020°C, 1 h solid-solution treatment. The aim of this study is to discuss the effect of various aging treatments for as-HIP treated 718 alloy. In the experiment, seven different aging treatments were used: 720°C for 2,4, 8 and 16h, furnace cooled to 620°C, soak for 8h, and air cooled to room temperature; 720°C for 8h, furnace cooled to 620°C, soak for 2,4,8 and 16 h, and air cooled to room temperature. Experimental results showed that 1020°C solid-solution, 720°C for 8 h and 620°C for 4h of aging treatment for as-HIP treated 718 alloy is optimum. AU the precipitations are MC carbides; the dimension of γ" precipitations is 30.41 nm, which with a maximum tensile strength (1407.2MPa) and elongation (14.5%) at room temperature. © 2010 The Japan Institute of Metals.