Duplex Surface Treatment of AISI 1045 Steel via Plasma Nitriding of Titanized Layer

In this study, surface of medium carbon steel (AISI 1045) was modified by titanizing followed by plasma nitriding. Titanizing was performed using pack cementation method, in a pack mixture of ferrotitanium, ammonium chloride and alumina, at 950 °C for 45 and 180 min. Plasma nitriding was conducted at two temperatures of 530 and 550 °C for 5 h, in a gas mixture of 75N2+2 H2 (vol.%). The samples were characterized by scanning electron microscope (SEM), X-ray diffractometre (XRD), Vickers microhardness and pin-on-disk wear tests. The thicknesses of titanized layers was 8-10μm, the thicknesses had no significant change after plasma nitriding. The duplex treated surface layers consisted of Fe4N, TiN and TiCN phases. Lower titanizing time and higher plasma nitriding temperature provided superior wear resistance and hardness. The highest wear resistance and the lowest friction coefficient were achieved in the sample which was titanized for 45 min and then plasma nitrided at 550 °C, with 2130 HV microhardness.