Two-stage carburizing cycle. In the boost the carbon potential is held high, often 1.1 to 1.2 percent, to load the surface fast; in the diffuse it drops to the final target, around 0.8 percent, so surplus surface carbon moves inward and the gradient flattens. It shortens cycles while avoiding carbide networks and excess retained austenite at the surface. Vacuum carburizing uses many short boost and diffuse pulses.
Run it boost and diffuse, 1.15 for four hours, 0.80 for two, then drop to 1,550 before the quench.
Also heard as
- boost-diffuse
- boost/diffuse
Related terms
Carburizing
Diffusing carbon into the surface of low-carbon steel at high heat, then quenching for a hard case.
Carbon potential
The carbon content a furnace atmosphere would give the surface of plain steel at equilibrium.
Vacuum carburizing
Carburizing at low pressure in a vacuum furnace using pulses of hydrocarbon gas, then a gas or oil quench.
Retained austenite
Austenite that fails to transform during the quench and survives at room temperature inside hardened steel.