Influence of η-(Ni3Ti) and TiC phases on corrosion resistance and mechanical properties of A286 austenitic superalloy after heat treatment
Usman Ali, Muhammad Saqlain Qurashi, Patrick Osei Lartey, Xi Jin, Junwei Qiao
Abstract
Eta [η-(Ni3Ti)] and TiC phases are formed in A286 superalloy during heat treatment process of this alloy. These phases have influence on corrosion and mechanical properties of this alloy, whose quantity and distribution depend on solution and aging treatment process. In this research, evolution of η-(Ni3Ti) and TiC precipitates effect are statistically analyzed after solution and aging heat treatment on different parameters. After aging, it is studied that how these phases effect corrosion and mechanical properties. Phases were identified by scanning electron microscope adjacent with energy dispersive spectroscopy and transmission electron microscope. During solutioning, homogenized distributions of TiC phases are achieved at 900 °C for 2 h. For aging, the lowest amount of η-phases formed in 710 °C for 5 h aged sample comparatively, this showed higher corrosion resistance and lower generation of donor densities during electrochemical tests. The prolongation of time and temperature during heat treatment leads to the formation of more precipitates. Alloy aged for lesser time and temperature (710 °C for 5 h) exhibited 55 MPa higher ultimate tensile strength compared to samples aged for higher temperature and time (750 °C with more time of 15 h). During fractography analysis, it is found that the brittle-intergranular fracture in prolong aged sample is initiated by eta-phases.