Vacuum Hardening

What is vacuum hardening?

Vacuum hardening is generally used to harden tool, die and martensitic stainless steels. It follows the same logic as quenching and tempering; the main differences are the equipment, the atmosphere and the quenching medium.

How is it done?

The steel is first placed under vacuum in a vacuum furnace. This prevents impurities from the atmosphere diffusing into the surface during heating. After evacuation, the furnace is brought to process temperature (850–1250 °C), where the austenitic transformation takes place.

Once austenitisation is complete, the steel is cooled and the martensitic transformation (hardening) is completed. Nitrogen, hydrogen or argon under high pressure, or oil, can be used as the quenching medium.

If needed, the hardened steel then goes through sub-zero treatment to remove retained austenite before tempering; otherwise it goes straight to tempering to reach the required hardness and stress level. After tempering, the material has the required hardness and microstructure and is ready for the next stage of production.

Which parts?

Cutting and forming dies, punches, hot-work dies, plastic mould parts, blades, and valve and pump parts made of martensitic stainless steel.

For a quote

State the steel grade (e.g. 1.2379, 1.2344), the part dimensions and weight, and the hardness range required after tempering in the quote form; attach a drawing if you have one.