Vacuum sintering furnace for cemented carbide

In many applications, the hard alloy is sintered by application. Sintered alloy surface friction often bear the harsh conditions and stress, in most of the applications in the metal cutting surface of the cutter head, wear depth more than 0.2~0.4mm, determine the tool has been scrapped, therefore, is very important to improve the surface performance of hard alloy.

Two basic methods of sintering cemented carbide:
One is hydrogen sintering, which is controlled by phase reaction in hydrogen and atmospheric pressure to control the composition of components.
The other is vacuum sintering using vacuum or reducing ambient gas pressure to control the composition of cemented carbide by slowing down the reaction kinetics. Vacuum sintering has a more wide range of industrial applications. Sometimes, hot isostatic pressing and hot isostatic pressing are adopted, and these technologies have important influence on the production of cemented carbide.
Hydrogen sintering: hydrogen is a reducing atmosphere, but when hydrogen reacts with the sintering furnace wall or bearing device, it will change other components and provide suitable carbonization potential to maintain the thermodynamic equilibrium with cemented carbide. In the traditional cemented carbide sintering, the carbon content of the carbide in the mixture is adjusted to the theoretical value, and the value is maintained during the whole hydrogen sintering process. For example, sintering 94WC-6CO cemented carbide, into the furnace, the carbon content is 5.70~5.80% (mass fraction), when released, is to maintain the atmosphere in 5.76+0.4% hydrogen sintering process control ability is sufficient for tungsten carbide cutting tools, but for steel alloy containing titanium carbide tantalum or niobium carbide. The oxidation potential of the atmosphere is too high, resulting in the changes of the alloy composition, usually by vacuum sintering to reduce the content of alloy, oxide, hydrogen sintering is commonly used in mechanical pusher way, through continuous sintering, use a single pre burning furnace to remove volatile lubricant to prevent the sintering process of volatiles after pollution. Pre sintering can also adjust the high green strength, can make the rough machining, for example, turning and drilling, pre sintering temperature at 500~800 degrees Celsius, which mainly depends on whether the removal of the lubricant thoroughly and required green strength.

Vacuum sintering: compared with hydrogen sintering, vacuum sintering mainly to several advantages, control the product components of the first vacuum sintering can be excellent, in under the pressure of 1.3~133pa, carbon and oxygen exchange rate between the atmosphere and the alloy is very low. The main factor affecting the composition change is the oxygen content in carbide particles, not the reaction rate between carbon and dilute gas in vacuum. Therefore, vacuum sintering has advantages in the industrial production of sintered cemented carbide.