Microstructure Evolution and Precipitation Modeling in Ni-Based Alloy C-263

Due to its high creep strength and oxidation resistance, C-263 is a promising Ni-based alloy for applications in superheater tubes in coal fired thermal power plants. The creep strength is mostly based on finely distributed gamma-prime precipitates. In this work, the microstructural evolution of this material during heat treatment and thermal ageing has been investigated. The investigations were carried out by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Selected Area Diffraction Pattern (SADP) and Energy Dispersive Spectroscopy (EDS). Besides, equilibrium and Scheil calculations were carried out using the thermodynamic software MatCalc to analyze the stable phases and the solidification process, respectively. Precipitation calculations during solution annealing and subsequent ageing at 700°C and 750°C up to 10.000h ageing time were performed to predict the phase fraction and precipitates radius. SEM and TEM investigations of aged specimens revealed three different precipitates: M23C6, γ’ and MX. MatCalc also predicted these precipitates. The calculated phase fraction and mean radius show good agreement with experimental data.