The Bureau of Mines investigated a method for increasing the leaching rate of bulk superalloy scrap to facilitate recycling and recovery of critical metals such as ni, CO, and cr. Three superalloys were investigated: cast nickel-base superalloy in-738, wrought nickel-base superalloy rene-41, and cast cobalt-base superalloy mar-m-509. Superalloys melted with 20%, 30%, 40%, and 50% al metal to form intermetallic compounds were easily crushed to a convenient particle size and dissolved rapidly in acid solutions. For example, leaching 1/2-in pieces of unalloyed in-738 with excess 6n hcl at 95 deg c for 2 h dissolved about 0.5%, While leaching 10 g of minus 20-mesh 30% al-70% in-738 with excess 6n hcl at 95 deg c for 2 h dissolved 96.2%.
Proc. 2nd Conf. Management of Municipal, Hazardous & Coal Waste, Sept. 1984, PP. 66-75