Tribological properties of pulsed ion nitrided AISI 4140 steel

The present study was conducted in order to investigate the tribological be haviour of plasma nitrided AISI 4140 steel by using a de pulsed glow discha rge technique. Microstructure and structural characterisations were perform ed by using scanning electron microscopy and X-ray diffraction techniques. A compound layer with a thickness between 6 and 8 mu m containing epsilon ( Fe3N) and to a lesser extent gamma' (Fe4N) was identified. Wear tests were performed with a pin on disc configuration. The tests were carried out at r oom temperature in air using two different pin materials (AISI 1086 and WC- 6Co). A sliding speed of 0.1 ms(-1), 5 N load, and 700 m maximum sliding di stance were used on both substrate and nitrided specimens. The friction coe fficients found for the tribological pairs under study, tungsten carbide pi n and plasma nitrided disc, AISI 1086 pin and plasma nitrided disc, and AIS I 1086 pin and AISI 4140 disc, were 0.34-0.6, 0.49-0.6, and 0.475-0.57 resp ectively. Wear volumes of 0.0453, 0.0511, and 0.00077 mm(3) have been deter mined for the tribological pairs mentioned above. The surface topography of the wear scars on both specimens and pins have been determined using scann ing electron microscopy and three-dimensional stylus profilometry. (C) 1999 IoM Communications Ltd.