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Case hardening - R.CARB+®


Not all case-hardening treatments are equal. RUBIG’s R.CARB+® processes have been used in the heat treatment sector for decades and still add optimum value. Tight tolerances and highest reproducibility are a given. Other advantages of R.CARB+® treatments by RUBIG include uniform hardness and dimensional stability.


You are interested in our case hardening processes?

Contact us.

RUBIG customers may choose from the following treatments:


Detailed descriptions of our procedures are presented in our technical data sheets that are available for download.

Benefits of R.CARB+® treatments for your components

  • Tight tolerances
  • Maximum reproducibility
  • Uniform hardness and dimensional stability
  • Standard or special heat treatments for your components

Case hardening R.CARB+®

Case hardening is a combination of a carburisation and hardening process including tempering. This results in a carburised edge surface with a carbon content of 0.6 - 0.8%. The carbon content decreases continuously towards the core.

The result of the hardening process is an edge with a high hardness and a soft, tough core. Materials suited for the carburisation process are so-called case-hardened steels with a carbon content below 0.25 weight by weight.


Suited materials:

  • Case-hardened steels


Advantages of case hardening R.CARB+®:

  • Increased fatigue strength
  • Increased wear resistance
  • Combination of hard, wear resistant surface and tough core


Typical components:

  • Gear components
  • Gear wheels
  • Shafts

Inert gas hardening

Inert gas hardening is a complete hardening process during which the components are protected within a reactive atmosphere against negative impacts of the edge zone (e.g. decarburisation). During the inert gas hardening, an oil bath is used for quenching purposes. This method is also applied to completely harden unalloyed and low-alloy steels.

With a subsequent tempering treatment, the characteristics (strength, toughness, wear resistance, ...) can be achieved within a broad range.


Suited materials:

  • Unalloyed and low-alloy steels (e.g. quenched and tempered steels 1.7225)
  • Ball bearing steel (e.g. 1.3505)
  • Carbon steels (e.g. C45)


Advantages of inert gas hardening:

  • Increased hardenability due to the oil quenching
  • In combination with the tempering a broad range of characteristics


Typical components:

  • Tools


Carbonitriding differs from case hardening in respect to the addition of nitrogen, i.e. the edge zone is concentrated with nitrogen in addition to carbon. This is followed by a hardening process incl. tempering in order to achieve the desired characteristics. In comparison to case hardening, the carbonitriding procedure provides the advantage that the hardenability is increased due to the nitrogen. Thus, unalloyed steels (construction steels) can be treated as well. As is the case with the case hardening, a hard, wear resistant edge surface with a high strength and a tough core is the result of the carbonitriding procedure.


Suited materials:

  • Steels with a low alloy content (e.g. construction steels)


Advantages of carbonitriding:

  • Increased hardenability as compared to case hardening
  • Increased fatigue strength
  • Increased wear resistance
  • Combination of hard, wear resistant edge and tough core


Typical components:

  • Gear components such as annulus gears, spur gears
  • Crankshafts
  • Drive shafts

High Carb

A special version of the carbonitriding is the "High Carb" procedure which results in a better hardenability and in particular in a tempering resistance due to a special process control.


During the carburisation procedure, the edge layer of a steel (normally case-hardened steels) is concentrated with carbon and not hardened subsequently in order to not achieve an increased hardness. This method allows the components to be processed which is followed by the actual hardening process. An advantage of this procedure is that it is possible with this sequence to manufacture components with different case depths. Materials suited for the carburisation process are case-hardened steels with a carbon content below 0.25 weight by weight.

Quenching and tempering

The term 'quench and temper' refers to a combination of a complete hardening procedure (e.g. vacuum or inert gas hardening) followed by a tempering procedure at high temperatures. Quench and temper is also known under the abbreviation "QT". The tempering treatment is performed at high temperatures of up to 700°C in order to achieve a good ratio of strength and toughness. Therefore, the quench and temper procedure is particularly suited and required for dynamically stressed components.


Suited materials:

  • Quenched and tempered steels
  • Nitriding steels
  • Tool steels (cold work, hot work and high-speed steels)


Advantages of the quench and temper procedure:

  • Good combination of toughness and strength


Typical components:

  • Tools
  • Moulds
  • Dynamically stressed components (e.g. shafts)


Refrigeration is particularly advantageous or required if components must meet the following requirements:

  • High resistance to wear:
    Refrigeration causes a conversion from residual austenite to martensite, resulting in an increased hardness.
  • Dimensional and form stability:
    With the refrigeration procedure a stable, homogenous structure is achieved which is not subject to changes or to minor changes only during its usage.


Refrigeration is normally performed at a temperature of -120°C and with dwell times of several hours. Another method is the so-called cryotreatment. During this procedure, the temperature is cooled down to -196°C and the dwell time exceeds the traditional heat penetration time by far.

Technical Data:

  • Maximum dimensions: 1.050 mm x 690 mm x 700 mm (L x B x H)
  • Temperatures: up to 690°C

More informations on request:[at]rubig[dot]com