Patent ID: 9212416
Filing Date: 2015-12-15
Classification: C23C

Abstract:
1. A process for surface hardening a workpiece made from stainless steel by gas carburization in which the workpiece is contacted with a carburizing gas at an elevated carburization temperature to cause carbon to diffuse into the workpiece surfaces thereby forming a hardened primary surface layer essentially free of carbide precipitates, wherein (1) the carburizing gas contains a carburizing specie comprising an unsaturated hydrocarbon, (2) the partial pressure of the carburizing specie in the carburizing gas is about 0.5 to 20 torr (˜67 to ˜2,666 Pa), (3) the total pressure of the carburizing gas is about 3.5 to 100 torr (˜500 to ˜13,000 Pa), (4) the carburizing gas also contains a companion gas, the companion gas comprising hydrogen, natural gas, propane, another C (5) the partial pressure of the companion gas in the carburizing gas is at least twice the partial pressure of the carburizing specie.