Polyphase sintering and properties of metal matrix composites

Examples of Fe–P, Fe–B polyphase sintered PM metal matrix composites have been considered. Microstructure and phase constitution of sinters have been tested. A special attention has been paid to Fe–Co–B cermets, which are the new PM metal matrix composites. The cermets were prepared from iron, cobalt, copper and boron powders mixture of different volume parts of these elements. Green compacts were sintered in different temperature and time. Such selection of sinters chemical constituents and sintering parameters made possible to carry out the sintering in two option in a solid phase, and with the participation of a liquid phase. The cermets produced were subjected to: metallographic tests, X-ray analysis, microanalysis, examination of hardness and of microhardness, as well as of wear tests in the process of sliding dry friction. Dilatometer analysis was used to control the basic phenomena taking place during polyphase sintering of investigated system Fe–Co–B. Cermets contain two phases: hard grains of iron–cobalt boride (FeCo)2B, or iron–copper boride (FeCu)2B (1800 HV) represents the reinforcement and a relatively soft and plastic eutectic mixture (FeCo)2B–(Fe–Co) or (FeCu)2B–(Fe–Co) (400–500 HV) been a matrix. The cermets chemical composition and sintering process parameters strongly affect the sintering mechanism and kinetics as well as cermets structure and properties. High hardness and resistance to wear of cermets were proved.