Effect of Carbides and γ/γ' Eutectic on Crack Initiation and Propagation in Ni-based Superalloy

Abstract

The Ni-based Udemit720Li superalloy tends to form large γ/γ' eutectic on grain boundaries (GBs) during solidification due to the addition of excessive Al and Ti elements, which provides convenience to study the effect of carbide and γ/γ' eutectic on crack initiation and propagation during tensile process. In this paper, Udemit720Li superalloy samples were prepared by induction melting casting method, arc melting and suction casting method. The microstructure, tensile properties and mechanism of crack initiation and propagation in Ni-based superalloy fabricated by two methods are investigated. The results exhibit γ/γ' eutectic accelerates the stress concentration at GB and thus leads to premature fracture failure. The samples with grain-boundary eutectic have higher strain hardening rate, but their cumulative and local misorientations are lower. For samples without eutectic at GB, the primary crack initiates at grain-boundary carbide along GB and extends along GB or into grain matrix, and exhibits better deformation performance and dislocation storage capacity within grains.