Strengthening of Low Carbon Alloy Steel Nitrided Gear by Generating γ’-Fe₄N Phase

Abstract

A high strength nitrided gear was developed in controlled gas-nitriding process for creating the γ’-Fe₄N phase compound layer and designing the material composition so as to minimize the hardness difference between compound layer and substrate, and to set the optimum hardness profile for the gear. The created compound layer is controlled around HV800 by low carbon steel with the Mn, Cr and V content in the material. As a result, the developed nitrided gear achieves at least 50% higher pitting fatigue strength than a conventional nitrocarburized gear, and same strength level with conventional carburized gear.