The process and its advantages
During vacuum hardening, alloy or high-alloy steel is heated and then quenched with gas in order to make the microstructure more robust. The result is a clean or bright metal surface that requires no or almost no hard machining. The process is well suited, for instance, for high-quality precision tools and moulded parts, or for cost-intensive individual tools.
The hardening process takes place in a special vacuum furnace, capable of delivering maximum temperatures up to 1,300 °C. Multi-chamber furnaces up to 1,000 °C are also suitable. The gas commonly used for quenching is nitrogen and, sometimes, helium.
Gas quenching produces less warping than quenching in oil or water. As alloy and high-alloy steels are largely air-hardening materials, they can form the martensite hardening structure in gas as well. Non-alloy and low-alloy steels are better suited for bright hardening with subsequent quenching in an oil bath.
The vacuum applied during vacuum hardening prevents the steel from reacting with the gases in the furnace during the hardening process. This prevents edge decarburising and edge oxidation.
The material is quenched using a precisely controlled stream of gas (usually compressed nitrogen) which is fed into the annealing chamber. This procedure makes it possible to thoroughly harden even sharp edges and large transitions in the cross-section because the gentle gas flow produces almost no warping in the component.
The state-of-the-art systems we use at Härtha allow us to automate and exactly repeat all steps in the process. Throughout the entire hardening process, the temperature of the material for hardening is controlled using thermocouples. We will team up with you to work out the relevant test specifications, and we guarantee maximum process reliability.
Summary: The advantages at a glance
- Little warping
- Metallic blank surfaces with no oxidation and no edge decarburising
- Great strength and resistance to wear
- Large cross-section transitions and sharp edges pose no problem
- Reproducible process
- Superior quality for precision components, moulded parts and high-quality tools
Combination with other processes
Vacuum hardening is frequently followed by the tempering process. This is used to precisely regulate toughness and hardness and thus set the individual wear resistance.
Moreover, the clean surface produced by vacuum hardening provides ideal conditions for targeted surface hardening by nitriding.
Stresses in the material can be created as early as the steel manufacturing process, and also during hardening or mechanical machining processes like machining or welding. These stresses can lead to cracks or undesired shape changes and warping. To relieve these stresses, stress-free annealing.
Applications and suitable materials
Because of the gentle gas quenching, vacuum hardening is used principally for hardening as well as quenching and tempering high-alloy steels. However, generally low-alloy steels can also be subjected to vacuum hardening, provided the component is small enough not to require the harsher quenching in oil.
Vacuum hardening is suitable for all air-hardening steels, and for hardenable acid-free and stainless steels, high-strength steels and hot and cold worked steels, in addition to high-speed steels.
Examples of suitable steels:
|Material number||Short name||Steel grade||HRC|
|1.2343||X37CrMoV5-1||Hot working steel||50-54|
|1.2344||X40CrMoV5-1||Hot working steel||50-54|
|1.4021||X20Cr13||Stainless martensitic steels||40-48|
|1.3207||HS 10-4-3-10||High-speed steel||63-65|
|1.3243||HS 6-5-2-5||High-speed steel||62-64|
- Toolmaking and mechanical engineering
- Medical instruments
- Mould construction
- Electrical industry and machine construction
- Automotive industry
- Aerospace technology
Type of system:
Horizontal vacuum system
1,200 x 1,500 x 1,000 mm (L x W x H)
Would you like us to perform vacuum hardening?
For us to perform vacuum hardening for you, we require the following information:
- Material designation
- Target hardness
- Dimensions of the component and batch size
- Test point
- Additional pre- and post-treatments
Together we will determine the parameters for the optimum treatment of your workpiece.