A microwave heating system configured to heat a plurality of articles and a process for using the same are provided. The microwave heating system includes a liquid-filled thermalization zone, a liquid-filled microwave heating zone, and a pressure lock system disposed therebetween. The pressure lock system includes a pair of locking gate valves and a pressure adjustment chamber configured to transition the articles being heated from the thermalization zone to the microwave heating zone, which may be operated at different pressures.