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Recycling Superalloy Scrap by Vapor Phase Zinc Embrittlement.
U S Pat 4 718 939 1988 Jan; :
A method of making superalloy scrap friable in order to allow greater recovery of metal values therein is disclosed whereby the scrap is treated with zinc vapor. After exposure to the zinc vapor, the metal scrap becomes friable so that it can be easily crushed. Thereafter, the metal values, particularly cobalt and nickel, can be easily recovered. The process can be made continuous by recovering and reusing the excess zinc vapor used in the treatment. Thus, 187 g of zinc were placed inside a furnace tube. A square-cell ceramic filter was sealed 3 in above the surface of the zinc. A 134 g turbine blade, a nickel-base alloy with Cr, Mo, and Nb alloying elements, was placed in the tube on top of the filter. The tube was sealed, evacuated, and heated to 900 deg c for 12 h, at which time the reaction of the turbine blade with the zinc vapor was substantially complete. Excess zinc was vacuum distilled from the tube and the tube was cooled to room temperature. The resulting product was friable, easily crushed to a powder, and contained less than 1 pct zn.
U.S. Pat. 4,718,939, Jan. 12, 1988
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Content source: National Institute for Occupational Safety and Health Education and Information Division