A tribological study of composite material based on iron with addition of calcium pyrophosphate

The paper deals with the problem of exploitative composite materials with solid lubrication additions. The goal of the present investigation was to research the composite materials based on iron powders with the addition of calcium pyrophosphate (Ca2P2O7). The influence of volume fraction of additions on compactibility, structure of composites and their tribological properties were examined. Tribological tests were performed by a special tribometer, which allowed to realise research during the periodically variable motion with low velocity and variable values of pressure. The rubbed surfaces were characterized with scanning electron microscope (SEM). The results shown that calcium pyrophosphate wield good influence on iron based composite materials. The addition of Ca2P2O7 changed the friction conditions and the mechanism of wear. In the case of non-modified sintered iron a complex sliding wear with predominant adhesive and fatigue character of damage has been observed, whereas the friction of the composite materials was accompanied by forming secondary layers due to the reactions of calcium pyrophosphate with wear debries in water environment. It ensured a significant decrease of the motion resistance and wear during friction.