Heat transfer during quenching into liquid is complicated when the quench medium forms a gas when heated to high temperatures.
The quenching process is usually split into 3 -5 stages.
Stage 1. Vapour blanket.
Depends upon surface roughness, quenchant temperature, quenchant type, oxidation. Heat transfer by radiation through vapour layer into quenchant.
Stage 1b. Partial film boiling.
Stage 2. Nucleate boiling.
Conduction and Convection.
Stage 3. Convection.
Dominated by heat transfer in the quenchant by convection which can be natural, forced with turbulence or forced with lamellar flow.