Renee Joost, Jüri Pirso, Mart Viljus Recycling of hardmetal scrap to WC-CO powder by oxidation reduction process

6^th International DAAAM Baltic Conference Industrial engineering, 24-26 April 2008, Tallinn, EstoniaThe processes of direct recycling hardmetal scrap by oxidationreduction technique have been investigated in details. The hardmetal scrap was oxidized in rotary tube furnace. The oxide powders were milled with graphite powder in ball mill. The carbon content was 6, 8 10, 11, 13 and 15wt%. The mechanism of the reduction of CoWO4 and WO3 with carbon (in the form of graphite) was studied in the temperature range 850 to 1020 °C in flowing N2 gas. The mass of the samples after reduction was ca. 30% lower. The reduced powder showed wide diffraction patterns of X-ray. The reaction of carburization was not completed in reduction process. From the carburized powder the samples were pressed and sintered in vacuum at 1420 °C. The microstructure (carbide grain size, porosity, free carbon and η- phase content) of the sintered parts was investigated by SEM. Key words: hard metal, WC-Co, recycling, carbothermal reduction