Tool Steel Hardening in a Vacuum Furnace: Benefits, Process, and Recommendations

In metallurgy, particularly when working with tool steel, the environment and process of heat treatment can dictate the final properties of the metal. Vacuum furnaces, with their controlled atmospheres and precise temperature settings, offer numerous benefits when hardening metals like tool steel, stainless steels, and high nickel-based components.

Benefits of Hardening in a Vacuum Furnace:

  • Enhanced Strength and Surface Integrity: Vacuum ensures minimal air and contaminants, preventing oxidation and decarburization. This results in stronger metals with bright, clean surfaces.
  • Corrosion Resistance: Stainless steels and high nickel-based alloys retain their innate corrosion-resistant properties due to the absence of unwanted oxide scales.
  • Temperature Stability: The consistent environment offers a stable temperature, ensuring optimal hardening effects.
  • Uniform Heating and Cooling: This minimizes distortion and promotes evenness in hardening, especially vital for tool steels where uniformity affects performance.
  • Cost-Effectiveness: Reduced post-process treatments and enhanced component longevity can lead to long-term savings.

Process Specifics:

Every tool steel alloy has its unique requirements, but a basic template for hardening in a vacuum furnace includes:

  • One or two preheat steps.
  • An austenitizing step.
  • A quench step.

Factors such as the material, part geometry, and distortion concerns influence the specific temperatures, times, and quench rates/pressures.

The key to successful tool steel hardening lies in the precise control of time and temperature. Each steel type has specific temperatures to reach its full hardness potential. The time spent at this temperature is also crucial and depends on the steel’s section size. Incomplete transformation due to inadequate time or temperature can lead to subpar hardness and wear properties.

The quenching process is equally crucial. A quench rate that’s too slow results in low hardness, while an overly fast rate can cause excessive distortion or even cracking.

Capability at ThermTech:

ThermTech boasts vacuum furnaces up to 72” in length with a maximum load capacity of 10,000 lbs. Our largest vacuum furnace provides a 15 bar maximum quench pressure. Notably, we are approved by both Ford and GM for aluminum die cast dies, and all our vacuum furnaces meet the AMS2750 standards for pyrometry. Our team is proficient in heat treating as per NADCA specifications.


While the tool steel hardening process might seem straightforward when following the steel company’s guidelines, its success hinges on the synergy between the steel supplier, tool maker, and heat treater. Effective communication between these parties is imperative. Feedback regarding distortion, performance, and other key parameters can then refine the hardening process, ensuring optimal outcomes for all involved.

ThermTech—Experts in Austempering Stampings, Machined Parts, and Investment Castings

ThermTech, Inc. offers both small and large batch capabilities for austempering steel and iron investment castings. Between our neutral salt bath furnaces and our larger austempering furnaces, we have the capabilities to austemper a wide variety of stamping, machined components, and investment castings. We have run austempering on alloys from 1060 through 4340 to ductile iron machined parts.

Our dedicated team works with you to ensure we meet your specifications. Count on our decades of experience with hardening, tempering, surface heat treatments, vacuum treatments, and annealing. To learn more about our services, please contact us today.

Learn more about austempering and how ThermTech can serve you by watching these videos.

Request a free quote online or call us at 800-752-6917. You can also contact us online for all your austempering and heat treating needs.

Error: Contact form not found.


ThermTech’s quality policy is ZERO DEFECTS for all customer products and in all quality management system activities. Through our efforts to continually improve the quality of the work we offer, we’ve been recognized as being able to meet the rigorous quality standards required by several of our major customers. ThermTech is certified for ISO 9001 and AS9100 in both Metal Heat Treat and Metal Finishing.