L&L Special Furnace Company Inc. has delivered an atmosphere-controlled retort burn-off furnace to a Midwest manufacturer of ceramic matrix composites (CMCs). The furnace, which has a work zone of 32 inches wide x 32 inches high x 66 inches deep, has a single zone of control with a temperature gradient of ±20°F at 1100°F using four zones of temperature control with biasing to balance any temperature gradients. The parts are heated to 1220°F (660°C) in a retort chamber that is pressurized with nitrogen. The byproducts of the outgassing part are directed by pressure and flow out of the rear of the furnace. The parts are then heated in a vacuum furnace to temperatures in excess of 2300°F (1260°C). The result is a super strong component that is lighter than titanium.

CMCs materialize when nano fibers of silicone carbide or other ceramic nano threads are wound together, forming various sheets and 3D-printed shapes deployed in aerospace and military applications. The resulting finished product is lighter and stronger than titanium. The nano threads in the CMC process are coated with proprietary resins that need to be completely removed from the substructure using heat. It is also important that there is no oxygen present during the process because it will significantly weaken the part structure.

The furnace is constructed of low-mass insulating firebrick, which allows for quicker cool-down times. The furnace is controlled by a Eurotherm Nanodac Mini 8 program mechanism with over-temperature protection. There is also a programmable flow panel to manage the nitrogen flow throughout the process. An independent flow panel is provided with an oxygen analyzer that monitors the oxygen content of the atmosphere on exit. This data is recorded electronically on the data-acquisition station.