Phase and microstructure formation in WC-Co cemented carbide tools via cold isostatic pressing

WC-Co cemented carbides exhibit a combination of high hardness, strength, and fracture toughness due to the synergistic composition effect of the hard tungsten carbide phase and the ductile cobalt binder. The cobalt binder typically contains both hexagonal and cubic polymorphic modifications, whose distinct mechanical and service properties make phase ratio control a key factor in enhancing tool performance. This study explores the use of cold isostatic pressing (CIP) of WC-Co green compacts before sintering as a method to enhance the properties of cemented carbides. A comparative analysis was carried out between cermets compacted via uniaxial pressing (UP) and those subjected to CIP before sintering. The results revealed that CIP significantly refined WC grain size in WC-8Co cermet, reducing it by 57 % from 2.3 μm to 1.0 μm. In both WC-8Co and WC-15Co cemented carbides, which were subjected to CIP, cobalt predominantly existed in the hexagonal polymorphic modification, in contrast to the cubic structure stabilized in alloys compacted solely by UP. Due to the structural changes, the mean transverse rupture strength (TRS) of CIP-ed WC-8Co and WC-15Co increased by 9 % (to 1980 MPa) and 13 % (to 2410 MPa), respectively. Cutting tools and burnishing tools were fabricated from WC-8Co and WC-15Co cemented carbides, respectively. Compared to tools compacted solely by UP, the wear rates of CIP-ed WC-8Co and WC-15Co tools were reduced by 67 % and 44 %, respectively. Overall, these findings demonstrate the effectiveness of CIP as a method for tailoring the microstructure of WC-Co cermets, significantly improving their wear resistance under severe contact loading conditions.