Material science and thermodynamics are applied in heat treating to achieve mechanical performance in gears. The technique includes part design, fixturing, and process development. Different furnaces may offer unique advantages, like minimizing part distortion, while operating and maintenance costs vary greatly for hardening furnaces. The challenge is to understand which furnace type can most effectively process the gear design and material grade. Protective-atmosphere furnace solutions are well-suited for hardening of gears. The process techniques include gas or vacuum carburizing, carbonitriding, and neutral hardening in a carbon-based atmosphere or in a vacuum. This paper will discuss vacuum, controlled atmosphere, and hybrid furnace types highlighting available processes while sharing respective associated operation and maintenance costs. Batch integral quench (BIQ) furnaces will be the base case for comparison, as they comprise the largest installed base for gear heat treatment. While a discussion of when to consider continuous atmosphere furnace equipment by defining what is high production versus today’s BIQ furnace capacities for gear heat treatment.