화학공학소재연구정보센터
Materials Science Forum, Vol.360-3, 649-654, 2001
Tungsten carbide iron aluminide hardmetals: Nanocrystalline vs microcrystalline
In this work an attempt has been made to replace the soft cobalt binder phase in WC hardmetals by harder and tougher Fe60Al40. Both WC hard phase and FeAl binder was made nanostructural by controlled ball milling of the particular microcrystalline starting material. Consolidation properties of microcrystalline powders with blended precursor powders of the same composition with both the WC and FeAl in nanocrystalline form were studied. Densification was achieved using uniaxial hot pressing. Powder blends containing 80 wt.% WC and 20 wt.% Fe60Al40 were liquid phase sintered to near full density using either nano-sized or micron-sized precursor powders. Consolidated material from blended nanostructural precursor powders showed significantly refined microstructures and improved properties. Pressure was found to be essential in densifying WC-FeAl composites when nano-sized binder was used. For ultrafine and nanostructural precursor WC powders pressure assisted sintering at 1450 degreesC resulted in segregation within the binder and the formation of an additional Al-rich phase. The reasons for this are unclear. Hardness values of the materials with nano precursor powders were higher than those of both conventional WC/FeAl and conventional WC-Co hardmetals. Results indicate that blended iron aluminide and nanostructural WC shows great potential for hot pressing into hardmetals with particular advantages over Co-WC. Characterisation methods used in this work included XRD, SEM, thermal analysis and bulk density measurements.