Using Carburising for Low Distortion

Case Hardening is Carburising. 

Gas Carburising and Carbonitriding are thermo-chemical heat treatment processes nominally carried out in the temperature range 800°c to 950°c. These processes change the chemical composition of the surface of a steel component so that subsequent fast cooling, by oil quenching, produces a hard “case” combined with a softer/ tougher core.

For better results in terms of distortion, for example, Low Pressure (Vacuum) Carburising and Carbonitriding (LPC & LPCN) delivers the same case hardening results as those from Gas, but under a vacuum and are quenched in special gases rather than oil.

LPC and LPCN process provide a cleaner, modern approach to gas carburizing and are often used where real precision and stability is required. Carried out within a vacuum, surfaces remain completely free from oxide and reduces the likelihood of micro cracks from initial wear in service. As the quenching process is at a slower rate, from gas rather than liquid, heat treatment distortion is minimised, thereby reducing the post heat treatment machining, grinding or straightening tolerances.
One major benefit is to the exacting removal of any potential IGO/ IGA (inter granular oxidation/ intergranular attack) which can be problematic with conventional gas carburising/ carbonitriding processes, and which promotes fatigue failure.

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Summary of advantages include:
  • No intergranular oxidation or attack
  • No decarburisation
  • Narrower range of carburising layer tolerance
  • Stable and highly consistent results
  • Accurate carburizing of blind and narrow holes
  • Minimisation of quenching deformations and distortion
  • Potential of using higher temperatures (over 950°c)
  • Clean finish
  • Environmentally friendly - no CO2 emissions

Low hardenability steels are rarely suitable for LPC/ LPCN, due to the slower quenching methods used, so correct steel selection is imperative. There are some materials specifically designed for the process and others that simply meet the requirements

Suitable steels include:

  • S155 & S156
  • EN39 & EN36
  • 819AW
  • NC310YW
  • W460
  • 35NCD16
  • C61 & C64
The most common components treated are:
  • Precision and Complex Gears – reduced grinding
  • Fuel Injectors – improved carburised case within small, deep holes
  • Fine or Complex parts – reduced distortion and cleanliness

specialised case hardening and low pressure vacuum heat treatments

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Aalberts Surface Technologies Heat Ltd | Disclaimer

Registered Address.: Aalberts Surface Technologies Heat Ltd, Blackhorse Road, Letchworth. SG6 1HD 

Tel: 01462 472147