Microstructure and high temperature mechanical properties of inconel 617

Abstract

Inconel 617 is a candidate tube material for high temperature gas-cooled reactors (HTGR). The microstructure and mechanical properties of Inconel 617 were studied after exposure at high temperature of 1050°C. The dominant oxide layer was Cr-oxide. The internal oxide and Cr-depleted region were observed below the Cr-oxide layer. The major second phases are M 23C6 and M6C types of carbides. The composition of M23C6 and M6C were determined to be Cr 21Mo2Co6 and Mo3Cr 2(Ni,Co)1C, respectively, by EDS. These carbides are coarsened during exposure. M6C carbide is more stable than M 23C6 at high temperature. There was not much change in mechanical properties after exposure at 1050°C for 1000 h.