The characteristics of μ phase precipitated during 720 °C long-term aging in alloy 617B

Abstract

In this work, the precipitation of μ phase is detected in alloy 617B during 720 °C aging for 10 000 h. The lattice parameters of μ phase is determined as a = 0.4720–0.4760 nm and c = 2.5394–2.5656 nm in this work. The μ phase in alloy 617B is mainly composed of Mo and Cr, in accompany with Ni and Co. The chemical formula of μ phase in samples aged for 5000 h and 10 000 h is (Ni0.031Co0.084Cr0.885)2.34Mo and (Ni0.030Co0.091Cr0.879)2.30Mo, respectively. The precipitation of μ phase competes with M23C6 carbide for Cr and Mo elements. Keywords: Nickel-base superalloy, Alloy 617B, μ phase