Vacuum Carburizing in a Pit Furnace: A 21st Century Solution to Large Component Case Hardening

Low pressure carburizing (LPC) is widely accepted as a robust case hardening process. However, its potential is limited by the suitably equipped vacuum furnace’s capacity. For the most part, LPC is conducted in horizontal vacuum furnaces where the opportunity to carburize large parts is limited. In this investigation, a new application of LPC in a large pit type vacuum furnace (capable of opening hot to air) shows the potential of LPC through the combination of it with a pit furnace to carburize more massive, large geometry components in a clean, effective and efficient process. The result is quality case-hardened parts without the undesirable gas carburizing side effects like a flammable atmosphere, intergranular oxidation, and limited retort life. The real advantage, however, is the decreased process time possible with LPC. The case study presented here shows that eliminating furnace conditioning and increasing process temperature can reduce processing time nearly three times and costs by half. Such reductions produce the potential for a one to two-year return on investment making LPC in a pit furnace a cost-effective option and more environmentally friendly (zero CO2 emissions) option to traditional gas carburizing technologies.