Abstract: Sulfurized layer，nitrided layer and nitrided with sulfurized layer are prepared on the 52100 steel surface by different plasma bombardment heat treatment technology in order to improve its tribological properties. A ball-on-disk sliding friction and wear tester is used to investigate the friction and wear properties of the original, sulfurized，nitrided and nitrided with sulfurized surface systemically. Micro-hardness tester is used to measure the hardness of different treated surfaces. Scanning electric microscope(SEM) is employed to analyze the morphologies of the worn surface. X-ray photoelectron spectroscope(XPS) is adopted to identify the valence state of boundary lubrication film and to detect the elements variation along with depth. The results show that plasma heat treatment can improve the tribological properties of 52100 steel under oil lubricated conditions. The 52100 steel substrate can not provide enough support to the sulfurized layer, so the lubrication effect of sulfurized layer is limited. The nitrided layer with high hardness has better friction and wear properties under lower load. The nitrided with sulfurized layer exhibits best tribological properties under harsh condition because the nitrided substrate can provide better supporting effect to sulfide layer.

Key words: Friction and wear, Ion nitriding, Ion nitriding with sulphuration, Low-temperature ion-sulphuration