The wear resistance of iron nitrides compound layers and a high nitrogen martensite phase formed in the material surface for industrial pure iron, treated by nitriding and quenching followed by aging process were studied experimentally. Both the compound layer without pores by lowering the nitriding temperature and the high nitrogen martensite phase, showed the same tendency to high wear resistance. On the other hand, the pores in the compound layer made by the longer nitriding time decreased the wear resistance due to the acceleration of crack propagation. Metal flows were observed at the ϵ-phase in the compound layer very close to the surface after a sliding test. However, no strain hardening was observed. It was also found that the metal flows on a large part of the martensite layer and the hardness increased considerably. These results revealed that the high hardness ϵ-phase shows high wear resistance due to the plastic deformation, whereas the nitrogen martensite shows high wear resistance by the plastic deformation accompanied with the strain hardening.
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