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Microstructure and wear behaviour of pulsed plasma nitrided AISI H13 tool steel

Recent years have witnessed an increasing usage of tool steels for industrial high strength applications. Plasma nitriding (PN) has been a flexible case hardening process compared with any other case hardening technologies. Literature has been found to be less secured in correlating generation and phase transformation of nitride phases with temperature and PN time and consequently their effect on different properties. In the present study, PN was applied with the aim to improve surface and near-surface property for three different PN time durations (6, 12 and 24 h). Surface properties of the plasma nitrided steel were evaluated by measuring hardness, roughness and wear resistance. Scanning electronic microscope (SEM) was used to reveal the microstructure and measure different layers after PN. X-ray diffraction enables identification of different phases along with its co-relation with different properties. PN with 6 h has been found superior based on wear resistant (0.0004 mg for 6 h compared to 12 and 24 h respectively 0.0005 and 0.0007 mg) & hardness (1107.66 HV for 6 h compared to 12 and 24 h respectively 1061.66 and 869.66 HV). Although microstructure revealed minimum case depth (minimum 107 µm for 6 h and maximum 220 µm for 24 h) and compound layer (6, 12 and 24 h are respectively 4, 6.5 and 11 µm), presence of unsaturated ϵ-Fe3N phase play an important role in governing the final property.