Vacuum Hardening – Process, Advantages, Alternatives

Vacuum hardening is a heat treatment for tool steels that takes place in a vacuum. A special vacuum furnace is used to heat the steel. Higher temperatures can be reached in the process than in a conventional furnace. Modern models can be heated up to a maximum temperature of 1300°C.

The aim of vacuum hardening is to create a hard, low-distortion and bright surface. The process is one of the air hardening techniques and often uses nitrogen as a quenching medium.

The Process

During vacuum hardening, the furnace and hardening material are heated simultaneously until the desired temperature is reached. This avoids excessive temperature differences between the hardening furnace and the component, which can lead to internal stresses building up. The temperature during treatment is increased in a controlled manner using control technology.

Nitrogen can be used as a medium in the process to enable uniform heat transfer during heating. Once the hardening temperature is reached, the steel is stopped for a predefined time. Thermocouples are attached to the component before treatment in order to control the temperature. It is common practice to attach these thermocouples not only to the surface, but also to the interior in order to control the temperatures throughout the steel body.

After heating and tempering, the steel is cooled or quenched using nitrogen. Depending on the steel grade, size and hardness result, quenching can be fast or slow.

Suitable materials

Hardening in a vacuum furnace is suitable for many tool steels, such as high-speed steels and cold work steels. The aim is to minimize distortion and improve surface hardness.

The treatment is well suited to alloyed and high-alloy steels, as the quenching medium nitrogen works more slowly and mildly than conventional oil and water.

Key Advantages of Vacuum Hardening

  • Improved product quality: Hardening in a vacuum means that the surface of the metal is not oxidized or discolored. You will therefore have a bright surface after the treatment and the component will not decarburize.
  • Controlled atmosphere: As vacuum hardening is carried out in an environment without oxygen, the temperatures and other conditions can be precisely controlled. The result is minimal distortion.
  • Environmentally friendly: Compared to many other processes, vacuum hardening produces less waste and emissions.
  • Efficient: Vacuum hardening can often be performed in a single step, making the process more efficient. It reduces the need for multiple treatments, saving time and costs.

Enhance Your Steel’s Performance with BorTec’s Advanced Hardening Services

Hardening using BORINOX® is a better alternative to vacuum hardening. The hardening process, which we have developed especially for steels and stainless steels, is not only suitable for tool steels, but also for most stainless steels, duplex steels and martensitic steels. The BORINOX® low-temperature process significantly increases surface hardness and wear protection without distortion.