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Vacuum hardening is a heat treatment process for metal components that uses a controlled vacuum or partial pressure, high heat and rapid quenching to improve strength, durability, surface brightness and cleanliness, stability and a variety of other properties. This process is exceptionally suited for metals including tool steel, stainless steel and titanium and is one of the quicker and most cost-effective heat treatment methods available.

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Equipment Used in the Vacuum Hardening Process

First and most importantly, vacuum hardening requires a vacuum furnace. A vacuum furnace is capable of reaching temperatures as high as 1,300 °C and creating and holding a low pressure or complete vacuum environment to prevent oxidation and contamination of the parts. Vacuum hardening often uses inert gases like nitrogen to quench the parts at a fixed rate based on the desired results. In addition to hardening, the equipment and conditions can be used for high-quality heat treatment processes like annealing, brazing, and sintering to produce parts with superior purity and minimal defects.

Vacuum Hardening Steps

During the process, the metal that’s being hardened is brought to temperature inside the furnace as it heats up, minimizing the potential stress that can be introduced when there is a large temperature difference. Depending on the metal and needed results, the parts will be held at temperature for a predetermined amount of time. Quenching is the final part of the process, which is most commonly done by introducing nitrogen or another inert gas to cool the parts. Quenching time is variable, depending on the desired results.

Every step of the vacuum hardening process is designed to prevent distortion, oxidation, scaling, decarburization, and other surface imperfections, resulting in improved wear resistance, stability, hardness, surface brightness and overall performance.

Best Metals for Vacuum Hardening

There are a number of good material candidates for this type of heat treatment, including:

• Tool steels
• 300 and 400 series stainless steels
• Titanium
• Alloys including 15-5, 17-4 and 17-7

Parts made from these materials and subjected to vacuum hardening are valued for their performance and reliability in a number of critical industries. For instance, parts hardened this way can be used for engines and turbines for the aerospace industry, various dies and cutting tools in tool manufacturing, precision instruments in the medical industry and transmission components and other parts that require tight tolerances in the automotive industry.