Liquid Phase Sintering of Ferrous Powder Metallurgical Materials

Abstract

Abstract Liquid phase sintering is an attractive means of reaching near full densification of sintered powder metallurgical materials. In order to successfully realise the desired densification and intended properties of the final sintered material, the tailoring of the powder composition, powder mixture and sintering cycle is decisive. One attractive way is to use an appropriate mixture of powder where at least one powder constituent - the master alloy powder - is given such composition that it fully or partially melts while another powder constituent - the base powder -remains solid. This classical way of persistent liquid phase sintering has been developed for various combinations of alloys of the Fe-C-P-Cu-Si system and results demonstrate the capabilities of reaching near full density for mixtures of powder of sizes commonly used for traditional uniaxial die pressing. Another way explored has been the design of sintering approaches for supersolidus liquid phase sintering of high speed steel powder. This approach has been extensively studied by several research groups and the benefit of in-situ nitrogen alloying during sintering to yield high density and the precipitation of vanadium nitride has been realised. In this study, this approach is explored for a high-vanadium alloy and the results show how almost full density with appropriate microstructure can be reached from pressureless-shaped specimens using so-called starch consolidation.