During the vacuum sintering process of the sintered mesh filter element, three obvious changes in the vacuum degree can generally be observed, that is, three large gas discharge processes in the cemented carbide sintered body.
The temperature at which the vacuum degree changes for the first time is about 350°C. The main reasons are: first, the gas adsorbed on the surface of the particles is desorbed under the influence of temperature and negative pressure; second, the forming agent in the compact volatilizes.
The temperature at which the degree of vacuum changed for the second time was about 1 100°C. The main reason for the significant change in the degree of vacuum was that the oxides in the compact were reduced by carbon (the reaction temperatures of WO3, TiO2 and C were 993°C and 1103°C, respectively). Generate CO gas.
The temperature of the third vacuum change of the sintered mesh filter element generally appears at about 1350℃. At this time, the furnace temperature is above the eutectic temperature, and a liquid phase appears in the sintered body. In a vacuum state, the liquid adhesive phase is prone to volatilization loss. Both theory and practice show that the furnace vacuum is high, the sintering temperature is high, the sintering time is long, the content of the bonding phase is high, and the carbon content in the sintered body is high, the greater the loss of bonding phase volatilization.
