Microstructures and properties of DZ40M Co-based superalloy after long-term ageing at 850 degrees C

DZ40M is a newly developed directionally solidified Go-based superalloy. Its microstructural characteristics and mechanical properties at room and elevated temperatures after ageing for 100 similar to 1000 h at 850 degrees C were studied. The results showed that 100 h ageing at 850 degrees C results in a substantial increase of tensile strength at room temperature and stress-rupture life at elevated temperatures, serious decrease of ductility at room temperature and improvement for stress-rupture ductility. With increasing ageing time, stress-rupture life tends to decrease and the other properties keep at essential constant. During ageing, primary carbides M7C3 and MC decompose sluggishly, fine M23C6 precipitates copiously around them and M6C forms on the surface of some M7C3. The increased strength of the aged alloy is attributed to a strong interaction between M23C6 and dislocations.