HIGH TEMPERATURE CREEP OF TUNGSTEN FREE COBALT BASED SUPERALLOYS

摘要

The current study reports the high temperature creep behaviour of the recently discovered123 Co-AI-Mo-Nb/Ta superalloys with additions of Ni, Cr and Ti. These alloys have a classical γ - γ' microstructure, where the L_(12) ordered γ' is present uniformly throughout the γ matrix of cobalt in the form of coherent precipitates. The γ' in these alloys, has been stabilized without the addition of tungsten. This results in lower density as well as easier homogenization treatment, since slowly diffusing tungsten is absent. The solvus of these alloys is beyond 1000° C. The alloys exhibit excellent mechanical properties at higher temperatures, with specific strengths that are attractive compared to commercially available current cast polycrystalline cobalt based superalloys.