bright hardening

Bright hardening is a hardening process in which steel is heated to a specific hardening temperature in a protective gas atmosphere and then typically quenched in an oil bath. This produces a uniform hardness level and prevents edge decarburising. It thus creates ideal conditions for the refinement of non-alloy and low-alloy steels. As it can be carried out fully automatically, a bright hardening process can be repeated as often as required. Would you like to schedule a consultation? Contact us!

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The process and its advantages

The objective of bright hardening is a uniform hardness increase in the treated workpiece. Heating the material to its austenitising temperature before cooling (quenching) it rapidly leads to the formation of martensite. The composition of the metal determines the corresponding austenitising temperature and cooling rate.


Info: Austenitising temperature
The austenitising temperature is the temperature at which steel and cast iron form austenite while being heated. If a hardening process is intended to produce martensite, the austenitising temperature corresponds to the hardening temperature.

The cooling process is followed by tempering (if the tempering temperatures are high, also referred to as quenching and tempering) to relax the stresses in the steel. During this process, we can customise such properties as toughness, strength, wear resistance, etc. precisely to your specifications.


Summary: The advantages at a glance

  • Maximum strength and toughness (including tensile strength and notch toughness, bending fatigue resistance, and fatigue strength)
  • Great resistance to wear and protection from brittle fractures
  • Exact control of carbon content
  • Prevention of edge decarburising
  • Computer-controlled processes: Every treatment is documented (thermocouples, mass flow controllers, quenching medium, etc.) and can be repeated as required
  • Most cost-effective hardening process

At HÄRTHA, we match all processes with the individual parameters of your workpiece.

Suitable materials

Bright hardening is suited for the through-hardening and refinement of alloy, low-alloy, and non-alloy steels. Virtually all hardenable steels, quenching and tempering steels, and nitriding steels can be treated.

The steel’s composition is decisive. The hardness achievable depends primarily on carbon content, and the hardness penetration depends on the variable components such as nickel, chromium, etc.


INFO: Hardness increase and hardness penetration
Hardness increase is the maximum hardness that can be achieved for a material. Hardness penetration represents the maximum hardness penetration depth at consistent quality.


Examples of suitable steels:

Material number Short name Steel grade HRC
1.7225 42CrMo4 Quenched and tempered steel
1.0503 C45 Quenched and tempered steel
1.2842 90MnCrV8 Quenched and tempered steel
1.3505 100Cr6 Bearing steel
1.2210 115CrV3 Bearing steel


Less suitable components and steels

  • Components with sharp edges or large differences in cross-section
  • Materials already hardened through (risk of fracture)
  • Surface-hardening steels such as C45 have only limited suitability – because the attainable hardness greatly depends on the shape of the workpiece

If in doubt, contact our team of experts. We look forward to receiving your enquiry.


INFO: Bright hardening vs. vacuum hardening
Low-alloy steels are not suitable for vacuum hardening, but through oil bath quenching, they can be subjected to bright hardening. However, the harsh quenching is likely to produce a certain amount of warping. For precision workpieces sensitive to warping, we therefore recommend vacuum hardening and the use of suitable steels.

Areas of application

Bright hardening represents metal processing which has a high degree of customisation and excellent quality. These attributes make this process appealing for the preparation of workpieces for key segments of industry and critical infrastructures.

  • Toolmaking
  • Mechanical engineering
  • Automotive
  • Medical engineering
  • Aerospace
  • Electrical industry
  • Warehousing industry
  • Agricultural machinery
  • Hydraulics

Process locations

Our locations in Germany and Europe are shown here.

Our system

Size of furnace:

600 x 900 x 600 mm (L x W x H)

Maximum batch weight:

600 kg

Maximum operating temperature:

1,050 °C

Processing time:

From 48 h, details upon request

Would you like us to perform bright hardening?

We need the following information from you:

  • Material designation
  • Required hardness (HRC) and tolerance
  • Maximum permissible warping
  • Additional pre- and post-treatments (e. g. nitriding, burnishing)

If a test area is stipulated, please send us a corresponding drawing, and add a note in your order.

Post-treatment and complementary hardening processes

Bright hardening is well-suited for combination with other treatments to refine and coat of workpieces. Burnishing, for instance, is suitable for ensuring corrosion protection and, thus, greater storage stability. In addition, nitriding is capable of producing hardness values greater than 68 HRC in the edge layer of heat-resistant materials. We will be happy to advise you on additional options.