Heat-treating processes and metal joining applications can significantly benefit from the introduction of microwave heating technology that uses plasma at atmospheric pressure. The new technology can be a very efficient, cost-effective heat-treating method compared with other microwave and furnace-based systems currently available. Microwave atmospheric plasma systems can reduce cycle times and eliminate the need for costly vacuum equipment required by other low-pressure microwave technologies.
Metals are generally good conductors of electricity, but react negatively when exposed to direct microwave energy, which often causes arcing that can damage heating equipment and the materials undergoing treatment. Other factors, aside from material composition, impacting heat-treating include the size, and mass of the object [Ref. 1,2]. These factors present significant challenges for microwave heating technologies. Key challenges included the development of a process able to harness microwave energy, without damaging magnetrons while evenly heating materials. Susceptor-based microwave heating tests produced mixed results, and also consumed considerable electricity. Microwave susceptors (e.g., ceramics) possess "inside-out" heating characteristics, which can lead to extremely high temperatures inside, and eventually produce a type of thermal runaway situation.