Gas carburising is a surface hardening process generally carried out at an elevated temperature above 925 degrees Celsius. Carburising is essentially the addition of carbon to the surface of low carbon steels at appropriate temperatures. Surface hardening is achieved by quenching the high carbon surface layer, which has good fatigue and wear resistance. Gas carburising in atmospheric environment is a process that is widely applied in cases where only surface hardness is required while maintaining the toughness of the steel.