Influence of heat treatment on Inconel 625 superalloy sheet: carbides, γ'', δ phase precipitation and tensile deformation behavior

• Published in: Journal of alloys and compounds 2023-01, Vol.930, p.167522, Article 167522
• Main Authors: Liu, Xudong, Fan, Jiangkun, Zhang, Peizhe, Cao, Kai, Wang, Zixiao, Chen, Fulong, Liu, Degui, Tang, Bin, Kou, Hongchao, Li, Jinshan
• Format: Article
• Language: English
• Subjects: Carbides; Gamma-double prime phase (crystals); Gamma-prime phase (crystals); Grain boundaries; Heat treatment; Inconel 625; Nickel base alloys; Phases; Room temperature; Strengthening; Strengthening mechanism; Stress concentration; Superalloys; Tensile deformation; Tensile properties; Tensile strain; γ'' phase; δ phase
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2022.167522

In this study, commercial Inconel 625 superalloy was subjected to solution and longer-term aged treatment. The effects of the temperature and time of aged treatment on the secondary-phase evolutions, tensile properties, and strengthening mechanism of Inconel 625 superalloy were systematically investigated. The results showed that the evolution of M23C6 carbides mainly included two paths: MC+ γ→M23C6 at 650 °C and MC+ γ→M23C6 + δ at 750 °C. The disk-like γ'' phase with three mutually orthogonal variants dispersedly precipitated within the grains after aged treatment at 650 °C for 200 h. After aged treatment at 750 °C for 100 h, the needle-like δ phase parallelly precipitated around the grain boundaries. As the aged time reached 200 h and 300 h, δ phases precipitated within the grains at the expense of the metastable γ" phase. Both γ'' and δ phases strengthened the alloy during tensile deformation at room temperature (RT). However, the γ'' phase showed a better strengthening effect than the δ phase. Coarsened δ phases would cause severe stress concentration around δ phase/matrix interfaces during the non-uniform deformation stage. With the increase of tensile strain, many microvoids appeared around the δ phases/matrix interfaces, which weakened the strengthening effects of the δ phases. •Carbide evolution paths at 650 °C and 750 °C were revealed.•The precipitation position of δ phase depends on the aging time at 750 °C.•The strengthening effect of γ'' phase is better than that of δ phase.•The optimum aging temperature for Inconel 625 alloy is 650 °C.