Reactions during preparation and sliding of sintered Fe-Mo-S wear-resistant materials

Using quick hot-press sintering, Fe-Mo-S materials were prepared with the properties of low wear rates (e.g. as an 8S28Mo64Fe pin sliding against a 45 steel disk in air, the specific wear of the pin is 8.6x10 super(-14) M super(3) N super(-1) M super(-1), while that of the disk is 1.21 x 10 super(-14) M super(3) N super(-1) M super(-1)). Using X-ray diffraction, X-ray photoelectron spectroscopy, Auger electron spectroscopy and differential thermal analysis, the reactions related to Fe-Mo-S materials were studied. Thermodynamic analysis of the reactions to form sulphides was performed. It was found that a non-stoichiometric Mo-S compound with a crystal structure similar to hexagonal MoS sub(2) and Fe sub(1.3)Mo sub(6)S sub(8) formed in the materials during preparation. Grey-black films formed on the wear tracks of the steel disks during sliding against Fe-Mo-S pins in air. Oxides are the major constituents and sulphides the minor constituents of the films. Comparing Fe-Mo-S materials and the alloys without sulphur (e.g. 45 steel or Fe-Mo alloy) indicates that the low wear rates of the materials are attributed to the formation of the films, and a catalytic effect of sulphides on the oxidation is a necessary condition in forming the films. The mechanism of improving the tribological properties by catalytic reaction films has been used successfully to develop Ni-Mo-S high temperature, self-lubricating materials.