Author(s)

R Sasai, A Santo, T Shimizu, T Kojima & H Itoh

Abstract

Development of new recycling system of WC- Co cermet scraps R. Sasai, A. Santo, T. Shimizu, T. Kojima, and H. Itoh Research Center for Advanced Waste and Emission Management (ResCWE), Nagoya University, Japan. Abstract In order to develop a new recycling system of WC-Co cermet scraps, dry and wet recycling processes were investigated. WC-Co cermet disks with 15 mmq5 in diameter and 5 mm in thickness were used as specimens, which contain ca. 20wtY0 of Co as a binding material. In the dry process, WC-Co tips were oxidized in air at 900°C to form the mixture of WO3 and Co3O4. The oxidized sample was ground with an appropriate amount of graphite powder by ball- milling, which was then reduced at 800OC in H2 atmosphere. The recovered powder was a mixture of WC and Co metal powders with a small amount of amorphous carbon. In the case of wet process, WC-Co disks were enclosed in concentrated HC1 aqueous solution and hydrothermally treated at 1 10°C for 48 hours. Co metal in cermet was completely extracted into acid aqueous solution as Co cations, while WC was collected as a porous solid. This phenomenon occurred by the difference in solubility between WC ceramics and Co metal into acid solution. This result indicates that WC and Co can be recovered separately by the wet process. 1 Introduction WC-CO cermet is an essential industrial material in the field of material processing for machining and working by cutting tools or dies. Today in Japan, ca. 3,000-4,000 tons/year of WC-Co cermet are produced and its annual usage is increasing year after year. Most of the WC-CO scraps are exported to foreign countries, and its recycling rate in Japan is decreasing. However, it is very important from the point of resource recovery in Japan to establish the material

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