Sintering Technology in Nanometer Tungsten Carbide Process
1) Vacuum Sinter
The vacuum sinter is to put the tungsten carbide products in the vacuum sinter furnace for sintering, when it gets the sintering temperature, the sample’s shrinkage reduces greatly with the increase of the holding time, which means the shrinkage for the sample is finished in the stage of vacuum sintering .Later,it make an apparently shrink to press it with 3Mpa pressure by taking hydrogen or nitrogen as gas medium. We can see that gas-pressure sintering plays very important role to promote the final densification, improve microstructure and eliminate porosity.
2) Spark Plasma Sinter
SPS is to make the grains in the sintered parts self-heating uniformly by the discharge plasma generated instantaneously by direct current pulse voltage ,which is a new technology to produce nanometer tungsten carbide with very significantly process advantages such as heat uniformity ,quick temperature rising ,low sinter temperature ,short sintering-time, high working efficiency, small uniform product organization,maintainance the nature state of raw materials ,improve densification of the material, available to sinter complex parts ,energy saving and environment protection.
3) Microwave Sintering
Microwave sintering enables the atom oscillation with the wave energy ,with which heat rising by friction of the atoms .It is characterized by changing temperature quickly ,and heat uniformly ,meanwhile avoid grain-growing in heat-transferring .In the sintering process ,it could help to skip surface-diffusion stage fast ,and achieve densification and cooling in short time. The nanometer tungsten carbide produced with microwave process have better microstructure uniformity, less porosity ,higher toughness and tensile strength by comparing with common sintered tungsten carbide products .According to the report ,it only takes 15~30 minutes to finish sintering process which is very critical to inhibit grain-growing of the nanometer tungsten carbide .
