In vacuum heat treatment, air (and oxygen) is removed from the furnace to create a vacuum. The part may be heated in the vacuum with or without an inert gas to achieve the desired properties while protecting the part's surface. As in traditional heat treatment, the metal is quickly cooled.
vacuum hardening offers the most controlled possible atmosphere, which often gives the best results In addition to avoiding damage, a vacuum hardening process can also improve many properties of metal parts. When materials treat with the vacuum process, it comes out harder and resists corrosion better. It also has more tensile strength, shear strength, ductility, and elasticity.