Low Pressure Carburising (LPC) is also known as Vacuum Carburising. Similar to other hardening processes, the purpose of Vacuum carburizing is to obtain a part with a tough and hard core, wear resistant surface. It is applied to increase the fatigue limit of parts working with continuous loading. Typical applications include gear parts, machine components, bearing components and injection systems for engines. Case hardening basically consists of three steps. The parts are austenitized, then carburized and quenched when the required carbon profile is reached, followed by an annealing step.

The LPC treatment takes place in a temperature range of 870 °C to 1050 °C and a pressure range of 5 mbar to 15 mbar. In most cases the vacuum carburising temperature is between 920 °C and 980 °C. During the entire process, the processed components are not exposed to any traces of oxygen.

As a carbon source, oxygen-free hydrocarbons such as acetylene C2H2 (ethine) are used. Hydrocarbons are injected into the furnace chamber, creating a pressure of several millibars. For complex shapes such as holes or even blind holes, it is recommended to use acetylene as it provides homogeneous carburising.

Usage Areas

The steels that vacuum carburising – carbonitriding process is applied in general are as follows.

  • 16MnCr 5
  • 20MnCr 5
  • 14NiCr14
  • 14NiCrMo 13-4
  • 15CrNi 6
  • 18CrNi 8
  • 17CrNiMo 6
  • 20CrNiMo 2-2 (AISI 8620)
  • 20MnB 5