Effect of η Phase on Mechanical Properties of the Iron-based Superalloy Using Shear Punch Testing

• Published in: ISIJ International Vol. 53; no. 2; pp. 311 - 316
• Main Authors: Seifollahi, Masumeh, Kheirandish, Shahram, Razavi, Seyed Hossein, Abbasi, Seyed Mahdi, Sahrapour, Peyman
• Format: Journal Article
• Language: English
• Published: Tokyo The Iron and Steel Institute of Japan 2013; Iron and Steel Institute of Japan
• Subjects: A286 superalloy; Applied sciences; Exact sciences and technology; fracture surface; Fractures; high temperature phase transformation; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; shear punch test; η phase; Shear test; Temperature; Shear; shear punch test; Rupture; Mechanical properties; high temperature phase transformation; High temperature; A286 superalloy; η phase; Superalloy; Phase transformation; Fracture surface
• ISSN: 0915-1559; 1347-5460
• DOI: 10.2355/isijinternational.53.311

In this paper, the shear deformation behavior of A286 Iron-based superalloy was studied with an emphasis on the influence of η phase on shear strength. The η (Ni3Ti) phase precipitates at high temperature heat treatment or during services at the expense of gamma prime phase. According to the microstructural features, no evidences of η phase were found at 650 and 720°C. η phase precipitated at 780 and 840°C and the amount of it increased with an increase the time and temperature. Because of using the alloy as fasteners, investigation of shear properties and the influence of η phase on it are indispensable. The shear strength of the alloy with different volume fractions of η was examined. It was found that, with an increase of η volume fraction, the ultimate shear strength decreases. The shear punch fracture surfaces were also examined by the scanning electron microscopy. The fracture surfaces of sheared samples indicated that low and high volume fraction of η phase result in interior cracks and grain boundary decohesion, respectively. In fact, the fracture of weak grain boundary films (η phase) produces this kind of decohesive cracking.