Sintering is the process in which the tungsten carbide grains are fused into the cobalt matrix by heating the green material (carbide that has not been sintered is called green) to a high temperature.

There are variations of the sinter process:
Hydrogen sinter, an early form of the sinter process where green carbide is heated in a form of hydrogen gas atmosphere, i.e. pure hydrogen, hydrogen/nitrogen gas mixture or dissociated ammonia.

Vacuum sinter, in this process the green carbide is heated in a vacuum furnace either at vacuum or in a partial argon environment.

Sinter-HIP, vacuum sinter with a post HIP operation, (Hot Isostatic Pressure). In this process the carbide is first vacuum sinter; at the end of the vacuum sinter process the vacuum is replaced by pressurized argon gas of many atmospheres. The vacuum sinter process creates a sealed envelope of molten binder metals around the carbide.

NOTE
Sinter-HIP should not be confused with a process sometimes called "post-HIP" or autoclave. In the Sinter-HIP process, sintering and HIPing are combined into a singe process step. In post-HIP the material is sintered then placed in a separate furnace to be re-heated and have pressure applied. Sinter-HIP takes place at much higher temperatures and lower pressure then post-HIP and is widely considered to produce a superior product.