Tungsten carbide (WC) is a high-performance material composed of carbon and the rare metal tungsten. It is used to produce hardmetals such as tungsten carbide cobalt, which has a hardness second only to that of a diamond. WC is a fine grey powder in its most basic form, but can be pressed and formed into many shapes, and melded with or grafted to other metals. The versatile powder is used to produce hardmetal tools needed in many different applications and across several industrial sectors, including automotive and aerospace manufacturing, construction, surface and underground mining, oil and gas exploration, and manufacturing. Hardmetal products are known to have a low porosity, very high hardness and considerable strength.
Pushing the limits
WC can be formed during a chemical reaction between tungsten and carbon at very high temperatures that range from 1 450 °C to, previously, 2 200 °C. This process is called carburisation. It is a challenge for plant manufacturers to reliably achieve these extreme temperatures in the thermal process equipment involved. During the EU-funded CARBIDE2500 project, the capability of this innovative furnace technology to achieve a maximum process temperature of 2 500 °C during carburisation was demonstrated. This is an increase in the previous maximum process temperature of 300 °C, up to a new high of 2 500 °C. The new technology enables the production of WC powder with a greater variety of characteristics and for a wider range of end products. “The new furnace technology should increase the availability of high-temperature WC powder, thereby facilitating research and development concerning the influence of process parameters, such as temperature on powder features,” explains coordinator Reinhard Schummers. “It is the first atmospheric pressure industrial furnace of its kind that is able to operate at 2 500 °C, 300 °C above state-of-the-art high-temperature industrial furnaces.”
Broadening available WC powder microstructures for hardmetal product development
In addition to demonstrating the achievement of the process temperature of 2 500 °C in the CARBIDE2500 furnace, project partners conducted material tests to compare the WC powder properties produced using the same input material at 1 600 °C, 2 200 °C and 2 500 °C. These demonstrations led to a wealth of experience gained concerning the potential for future research into the influence of the relevant process parameters. “Offering a small-scale furnace in which the conditions are the same as those in an industrial one should make it easier for product development to be carried out with regard to the carburisation of tungsten,” notes Schummers. The WC powders carburised during the project in the CARBIDE2500 furnace were analysed in detail. “The 2 500 °C WC powder was found to not only have a correspondingly coarser grain size due to the significantly increased grain growth,” adds Schummers. “The powder microstructure was also found to be unique.” The furnace technology will lead to greater flexibility in relation to the process parameters during the carburisation procedure. “Potentially, this will result in WC powder with a broader range of material characteristics becoming available on the market,” he concludes.
CARBIDE2500, WC, powder, furnace, tungsten, carbide, carburisation, tungsten carbide