Abstract Pre-oxidation was adopted as a pretreatment prior to gas carburizing for 18CrNiMo7-6 steel, and its effect on the carburizing efficiency and internal oxidation was evaluated in this research. The… Click to show full abstract
Abstract Pre-oxidation was adopted as a pretreatment prior to gas carburizing for 18CrNiMo7-6 steel, and its effect on the carburizing efficiency and internal oxidation was evaluated in this research. The results indicated that pre-oxidation could improve the carburizing efficiency and result in much thicker effective case depth than that without PO pretreatment under the same carburizing condition. Meanwhile, the thickness of internal oxidation layer decreases significantly by PO pretreatment. The enhanced carburizing efficiency and decreased internal oxidation tendency could be ascribed to the oxide layer formed on the surface and the higher surface free energy (SFE) by pre-oxidation (PO).
               
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