Abstract
To develop a novel recycling process of WC-Co cermet scraps, hydrothermal oxidation treatment of various WC-Co cutting tools was investigated. Four kinds of WC-Co chips were used as samples: the sample A contained 13% of Co and was fine-grained, the sample B contained a small amount of TaC (ca. 1.5%) in addition to 6% Co, and the samples C and D were coated chips on normal WC-Co substrates. The sample was enclosed in a high pressure container lined with polyfluorocarbon resin with an appropriate concentration of nitric acid in the presence and absence of fluoric acid. As a result, pure WO3 powder was selectively recovered from all samples by the hydrothermal oxidation treatment in 7mol/dm3 HNO3 and 2mol/dm3 HF mixed aqueous solution. Other elements such as Co, Ta, etc. were dissolved into the solvent. In conclusion, the present hydrothermal oxidation method was found to be one of the superior methods to recover W and Co resources from WC-Co cermet scraps.
