High-temperature Treatment Process for Used Hard Alloys

High-temperature treatment of hard alloys is carried out in a specially designed high-temperature furnace. The waste alloys are subjected to high-temperature processing above 1800℃ in a protective gas atmosphere. During this process, the cobalt used as the binder metal liquefies and boils, causing the alloy to deform and its volume to expand significantly. The alloy structure becomes porous and honeycomb-like, making the hard alloy extremely easy to break and process. During the high-temperature treatment, a large amount of liquid phase appears in the alloy, intensifying the diffusion of atoms and enhancing the dissolution and precipitation of WC. The WC grains grow rapidly, increasing from 1 to 2 μm to tens or even hundreds of micrometers. Moreover, during the recrystallization of WC, the defects in the grain structure are eliminated, and the WC crystal structure becomes more complete. At the same time, the trace amounts of other metals, non-metallic impurities, and harmful impurities originally contained in the alloy are removed.

The grain size of the alloy increases rapidly with the increase of the high-temperature treatment temperature. However, when the treatment temperature is constant, the extension of the treatment time has no significant effect on the increase of the alloy grain size. The grain size of the alloy changes with the treatment temperature and holding time after high-temperature treatment. The key to controlling the high-temperature treatment process is to control the treatment temperature. But the treatment temperature is not necessarily the higher the better. If the treatment temperature is too high, it will first affect the service life of the high-temperature equipment; secondly, it will cause too much liquid phase in the alloy, increased volatilization of the Co phase, collapse of the WC skeleton, and make the alloy integrate with the crucible, making it difficult to clean and break. Generally, the high-temperature treatment process is controlled at around 2000℃, and it is advisable to hold for 2 hours.