Analytical Electron Microscopy Studies of the CMSX-4 Single Crystal Superalloy Subjected to High Temperature Annealing

The aim of the present work is to investigate the development of the γ/γ' microstructure and the changes in chemical composition of γ and γ' phases during high temperature annealing of CMSX-4 superalloy at a temperature of 1100°C in the time range from 500 to 2500 h. The studies were performed by means of scanning electron microscopy and the modern scanning-transmission electron microscopy with Super-X EDS system of four SDD detectors. Results of scanning electron microscopy and scanning-transmission electron microscopy analyses have shown that the microstructure of CMSX-4 superalloy is unstable during ageing at high temperature and the coalescence of cuboidal γ' precipitates was observed. Energy dispersive X-ray microanalysis revealed the distribution of particular alloying elements in the γ and γ' phases and the differences in their concentration in the function of the annealing time.