A common use of a vacuum furnace is for the heat treatment of steel alloys. Many general heat treating applications involve the hardening and tempering of a steel part to make it strong and tough through service. Hardening involves heating the steel to a pre-determined temperature, then cooling it rapidly.

Vacuum furnaces are ideal for brazing applications. Brazing is another heat-treating process used to join two or more base metal components by melting a thin layer of filler metal in the space between them.

A further application for vacuum furnaces is Vacuum Carburizing also known as Low Pressure Carburizing or LPC. In this process, a gas (such as acetylene) is introduced as a partial pressure into the hot zone at temperatures typically between 1600F and 1950F. The gas disassociates into its constituent elements (in this case carbon and hydrogen). The carbon is then diffused into the surface area of the part. This function is typically repeated, varying the duration of gas input and diffusion time. Once the workload is properly "cased", quench is induced typically using oil or high pressure gas (HPGQ) typically, nitrogen or for faster quench helium.

This process is also known as case hardening.