Some Observations on the Recycling of Superalloys by the EBCHM Process

Abstract

The casting of DS and single crystal superalloy components generates a considerable proportion of scrap in alloys which are extremely expensive. Most specifications forbid the extensive re-use of recycled materials on the grounds that they are contaminated in such a manner as to affect the castings which might be made from them. The effect of impurities (principally oxygen and nitrogen) is not well defined but may appear as increased microporosity, rejectable non-metallic inclusion clusters or an enhanced propensity for the formation of freckles and random grains. The purpose of this work is to analyse the defect formation in recycled alloys and also the necessary refining to eliminate it in the cases of two specific alloys, IN100 and MAR M247. It is concluded that the required refining can be achieved for a 100% recycled charge by the use of the electron-beam cold-hearth refining process.