Liquid generation during sintering of Fe–3.5%Mo powder compacts with elemental boron additions

Abstract The mechanisms for liquid generation and the microstructural development during sintering of a Fe–3.5Mo–0.3B alloy were studied. Interrupted sintering experiments followed by water quenching from specific temperatures within the sintering cycle have been carried out. The influence of Mo, both, on the final microstructure and on the behaviour of boron prior to, during and after the formation of the liquid phase, was studied through observation of the quenched samples under LOM and SEM. The study shows that prior to the formation of the liquid phase, boron diffuses into the metallic particles forming inter and intragranular precipitates of the (Fe,Mo)2B type. At higher temperatures a continuous Fe/Mo/B liquid phase, with excellent wetting characteristics, is formed thus leading to near fully dense materials. The generation of the liquid is based on a eutectic reaction involving the mixed (Fe,Mo)2B borides previously formed. The development of the microstructure after liquid formation is described.