Precipitation of carbides in a nickel-based cast heat-resistant alloy during thermal exposure: evolution of microstructure, hardness and corrosion properties

Ni-based G-NiCr28W alloy, which is widely preferred in high-temperature applications, has an austenite matrix as well as carbides dispersed in the structure. The morphology of the carbides in the structure varies depending on the chemical composition and heat treatment. Carbide phases commonly seen in these alloys are MC, M7C3, and M23C6. These carbides can transform into each other and the mechanical properties of the alloy can be affected by the carbide transformation. In this study, the effects of the carbides on the morphology, distribution, and strength of the alloy were investigated following the solution treatment applied at different temperatures and durations. Samples were characterized by light metal microscopy, SEM, EDS, XRD analysis, hardness, and potentiodynamic polarization tests. After the process, due to the excess of more stable carbides and their homogeneous distribution within the structure, the highest hardness and corrosion values were revealed in the sample that was processed at 1000 & DEG;C for 100 h.