Many scholars have tried new methods to reduce production cost. The direct synthesis of tungsten cobalt alloy powder from ammonium metatungstate is an innovative attempt.
A New Shortcut for Preparing WC-CO Powder from Ammonium Metatungstate
By ammonium metatungstate direct synthesis of WC-CO powder the process is roughly using ammonium metatungstate (APT), soluble cobalt salt and organic carbon source as raw materials, using spray conversion method, preparation of tungsten cobalt precursor by direct carbonization in situ synthesis method, the precursor for WC-CO carbide composite powder. The technology greatly simplifies the process of traditional technology, the cost is also reduced in theory.
Some scholars using the preparation of ammonium metatungstate by AMT (WO3>92.5%), soluble cobalt salts and ultra pure organic carbon as raw materials, according to the wc-6% (mass fraction) CO composition prepared tungsten cobalt mixed solution, and then the preparation of tungsten cobalt precursor powder in spray drying tower, calcined in N2 atmosphere, finally prepared by in situ synthesis method prepared by direct carbonization of WC-CO composite powder in H2 atmosphere. For the spray conversion, the calcination process uses fixed parameters: the solution concentration is set to 60% (mass fraction), feed rate 2000ml / min, inlet temperature 240 °C, centrifugal speed 12000r / min, low temperature calcination temperature is set to 200 °C; Set the direct carbonization temperature to 800, 850 and 900 °C. In situ synthesis of WC-CO powder by direct carbonization.
On the set of carbonation temperature test found that W at 800 °C began to slow carbonation, with the temperature rise, carbonization speed, to 900 °C, W has been carbonized more complete, under normal circumstances, W need to be carbonized at 1100 °C, but here the carbonization temperature is reduced by 200 °C, the main reason is that CO on the carbonization of W play a catalytic role.
The process of preparing WC-CO powder from ammonium metatungstate was carried out along the W / CO / C → WCO3 · CO6W6C → W2C-CO → WC-CO reaction. The WC-CO composite powder with hollow spherical structure can be successfully prepared, the average particle size is about 30 um, and the hollow sphere wall thickness is about 1.8 um; With the increase of carbonization temperature, the reaction system can be directly generated W2C-CO without further two steps, and then further carbonized into WC-CO composite powder.
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