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Vacuum Heat Treatment

A process of altering the physical or chemical properties of a material, by heating it to high temperatures in a furnace under vacuum.


What is vacuum heat treatment?

Over time, any material absorbs the air it is exposed to along with the dust and water vapor the air contains. The material reacts chemically, and oxides, nitrides or other undesirable compounds are produced. These may be considered as impurities or contamination.

Heating the material under vacuum allows to clean and protect it. This is possible as contaminants will either vaporize when being heated or decompose thermally in the absence of oxygen. The impurities and contaminants disassociated in this way can then be removed from the furnace with the help of vacuum.

The advantage of heat treatment under vacuum is that no costly or flammable gas atmospheres such as Hydrogen or Argon are needed to prevent the material from oxidation when it is heated.

Vacuum Heat Treatment Process in Vacuum Furnaces

A vacuum furnace consists of a sealed chamber where the heat treatment process takes place. The chamber is connected to a vacuum system that removes nitrogen and oxygen, preventing oxidation and contamination of the processed material.

Common types of heat treatment in vacuum furnaces include annealing, precipitation hardening, tempering, normalizing, and stress relieving. Each process is carried out in several steps, depending on the requirements of the material being handled. The steps include heating and soaking at specific temperatures and cooling at exact rates. This ensures that the desired properties, as well as a bright, contamination-free finish, are attained.

Vacuum heat treatment in vacuum furnaces ensures consistent and high-quality products, ideal for industries such as aerospace and automotive as well as hospitals and healthcare facilities.


For use in vacuum heat treatment Busch offers individual vacuum pumps as well as complete vacuum systems including piping and control. Vacuum systems for heat treatment typically consist of three elements: a backing pump, a vacuum booster and finally a diffusion vacuum pump designed for high vacuum levels.
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Learn more about heat treatment under vacuum

How does vacuum heat treatments work?

Vacuum heat treatment is the process of thermally processing materials under vacuum. To prevent contamination or to enhance the physical, chemical, or metallurgical properties of the material being heat-treated.

What are vacuum furnaces?

Vacuum furnaces are specialized types of furnaces that are used for high-temperature heating processes in an environment that is free of air or other gases.

Where can vacuum heat treating be used?

Vacuum is used inside the sealed vacuum chamber in which the heating takes place. A fully automated vacuum system is used to generate the needed vacuum. A control system allows to monitor and adjust the vacuum level to perfectly suit the respective heating cycle and application. For example, some materials will require degassing once they reach certain temperatures, therefore the control system will heat up and hold the product at this temperatures for a defined period of time to let the gas evolution take place. The dimensioning and design of the vacuum pump is critical to ensure the pump can handle the gas load of both, the product and the furnace.

What are the advantages of vacuum heat treatment?

The clean environment prevailing under vacuum is ideal for many metallurgical processes such as brazing, diffusion bonding, sintering, and hardening. Various advanced and complex materials like Titanium, Inconel as well as high-quality stainless steels and their alloys are processed under vacuum. This allows to create a product with a bright, oxide-free finish.

What are the best vacuum pumps for heat treatment?

Vacuum heat treatment furnaces typically require a system composed of three types of vacuum pumps: The most frequently used vacuum pumps for the first stage are dry screw vacuum pumps. Vacuum boosters are then used to reach a lower operating pressure. High vacuum is finally achieved using a diffusion vacuum pump.

How do vacuum furnace heat treatment systems work?

A vacuum furnace system usually consists of the following core components:

  • A vacuum chamber used to maintain the vacuum environment.
  • A hot zone which is an insulated resistance heater used to heat materials to 1,200 °C for most applications and to over 2,000 °C for some specialized processes. The insulated resistance heater consists of a series of heating elements made from high-temperature materials such as Inconel, graphite, Molybdenum or Tungsten depending on the process temperature and application. The elements heat up by way of resistance to electrical current. To prevent heat losses inside the hot zone, a thermal insulation barrier is used suitable for both, vacuum and high-temperature environments.
  • A vacuum system delivers the required vacuum. It mostly consists of a backing pump, a vacuum booster, and a diffusion vacuum pump.
  • A gas quenching system used to cool the product rapidly at the end of the cycle thus improving material properties or cycle times. The product can also be cooled by building the vacuum chamber described above as pressure vessel. For cooling purposes, this vessel is filled with high-pressure gas at the end of the cycle.
  • A digital control system based on Programmable Logic Controllers (PLC) and Supervisory Control and Data Acquisition (SCADA).
  • A water cooling system that allows to keep the furnace cool during operation.

What are the key points to consider when buying a vacuum system for heat treatment?

There is no one-size-fits-all solution when buying a vacuum heat treatment system. The following parameters have to be taken into account to provide the most efficient solution:

  • heating power
  • operating temperature
  • process and material compatibility
  • temperature uniformity
  • gas purity and dew point
  • gas cooling speed
  • furnace classification (for aerospace applications)
  • pump-down time and vacuum level
  • safety features
  • loading and load fixturing
  • plant layout and ergonomics

Which vacuum pumps from Busch are especially suitable for heat treatment processes?

The choice of the vacuum pump depends on the respective process requirements. Most suitable products are COBRA dry screw vacuum pumps, R5 oil-lubricated rotary vane vacuum pumps and RANGU diffusion vacuum pumps as well as PANDA/PUMA vacuum boosters.

What are some examples for the use of Busch vacuum technology in heat treatment applications?

Busch vacuum pumps are used as standard in many thermal processes. From high performance vacuum brazing of aeroengine components to chemical vapor infiltration of carbon fiber brakes for aerospace and motorsport applications, Busch offers a wide range of vacuum systems tailored to each specific application.

How does vacuum heat treatments work?

Vacuum heat treatment is the process of thermally processing materials under vacuum. To prevent contamination or to enhance the physical, chemical, or metallurgical properties of the material being heat-treated.

Heat treatment in practice

  • Reliable Vacuum Supply for Plasma Nitriding

    Reliable Vacuum Supply for Plasma Nitriding

    HWL Löttechnik GmbH

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