Thermal oxidation behavior of WC-Co hard metal machining tool tip scraps

The thermal oxidation behavior of scraps of WC-Co hard metal machining tool tips, which have worn in high speed machining of metals or alloys, is investigated with a view toward recycling WC-Co tool tip scraps into W and Co resources. Oxidation is a preliminary process in eco-friendly dry recycling of scraps including rare metals. High oxidation rate of the WC-Co tool tip scraps is achieved when they are fragmented into many pieces to avoid the resistance to oxidation of a protective CrAIN coating. WC-Co compound scrap is oxidized to WO3 and CoWO4 with a weight gain of 20% compared to its initial weight during isothermal oxidation at 900 degrees C. It experiences a large volume expansion of more than 200%, producing a porous microstructure. Fragmented WC-Co scraps are oxidized in a parabolic-like behavior, whereas the initial gradual oxidation of mechanically untreated WC-Co scraps is followed by a rapid oxidation after 1.5 h due to the breakdown of the CrAIN coating. (C) 2012 Elsevier B.V. All rights reserved.