Meaning
Chemical additive materials added to tungsten carbide composites suppress the recrystallization of grain boundaries during thermal densification. Industrial manufacturers introduce chromium carbide inhibitor to prevent the detrimental enlargement of tungsten carbide particles in hardmetal tool production. This additive limits the mobility of grain boundaries during liquid phase sintering.
The effect minimizes localized structural flaws that reduce fracture toughness.
Solubility Limit
Dissolution behaviour in the cobalt binder phase determines the concentration required to arrest grain boundary movement. Adding a chromium carbide inhibitor beyond its saturation point results in the precipitation of tertiary carbide phases that degrade mechanical properties.
Microstructure Control
Restricting the development of anomalous grains ensures uniform hardness and wear resistance across the sintered compact. Incorporating a chromium carbide inhibitor produces a fine grained microstructure necessary for precision machining applications. Sintering without this control leads to rapid growth of isolated grains.
Such microstructural defects act as stress concentrators during mechanical load.
Sintering Phase
Solid state activation begins before the cobalt binder melts to form the liquid phase that densifies the composite. Sintering temperature governs the transport rate of the chromium carbide inhibitor to the grain interfaces. The additive segregates to these boundaries and forms a thin layer that acts as a physical barrier.
This blocking mechanism remains active throughout the cooling cycle, which prevents subsequent coarsening as the liquid solidifies.
