A vacuum furnace having a heating chamber for heat treating work parts under vacuum therein, and a cooling chamber located adjacent to the heating chamber for receiving the heat treated work parts for the rapid cooling thereof, the work parts being rapidly cooled in the cooling chamber by the circulation of a cooling gas therein, a high-velocity fan being provided in the cooling chamber for the rapid circulation of the cooling gas over the work parts, heat transfer means located in the cooling chamber and over which the cooling gas is circulated for withdrawing heat therefrom after the passage of the gas over the work parts, and a unique door arrangement being located in the cooling chamber to insure the sealing of the cooling chamber both during the evacuation thereof upon transfer of the work parts thereto and during the cooling cycle therein, whereby in the cooling cycle the pressurized cooling gas within the cooling chamber acts to seal an inner door so that the use of exterior clamps and/or locks for sealing the cooling chamber is avoided.