MICROSTRUCTURES AND PROPERTIES OF DZ40M Co-BASED SUPERALLOY AFTER LONG-TERM AGEING AT 850℃

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DZ40M is a newly developed directionally solidified Co based superalloy. Its microstructural characteristics and mechanical properties at room and elevated temperatures after ageing for 100～1 000 h at 850 ℃ were studied. The results showed that 100 h ageing at 850 ℃ 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 M 7C 3 and MC decompose sluggishly, fine M 23 C 6 precipitates copiously around them and M 6C forms on the surface of some M 7C 3. The increased strength of the aged alloy is attributed to a strong interaction between M 23 C 6 and dislocations.