Using recycled superalloys in precision casting

The recycling of cast scrap is not uniquely justified by fear of difficulties in supplying primary metals or by care to preserve the relationship limited natural supplies of certain of these materials: it is imperative that the smelter minimize costs. Recyling can, however, lead to a deterioration of the metallurgical properties of precision cast superalloys and to a certain chemical contamination that can affect the service life of cast parts. Recycling can be introduced only after careful control of all the consequences. The influence of recycling on composition (trace elements), solidification behavior, microstructure, and mechanical properties was investigated in various nickel alloys such as IN 100, IN 728, and Mar-M-002. Cobalt alloys such as X45 and W152 were also studied. Particular emphasis is given to inclusion content and to the tendency to microporosity. The technical occurrence and economics of an eventual hot isostatic compression cycle is evaluated.