Properties and performance of spark plasma sintered, laminated WC-Co cutting tools

Abstract

The goal of the study was to fabricate laminated WC-Co cutting tools with residual thermoelastic stress states tailored to counteract the thermal and mechanical stresses imposed by machining. Cutting tools were fabricated using tape casting and bulk powder compaction of submicrometre and nanograin WC-Co powders. The weight fraction of cobalt in the tool was graded to produce residual compressive stresses in the tool surface. Spark plasma sintering (SPS) was used to fully densify the laminates while suppressing cobalt redistribution via sub-eutectic (solid state) sintering. Microstructural analysis showed that the cobalt binder was not well distributed around the WC grains after sintering. Contiguity of the WC grains was high, and segregation of cobalt was apparent. These factors are expected to hinder machining performance. However, the laminated tools performed similarly to commercially-available, monolithic tools in turning Ti-6Al-4V alloy. This demonstrates that the incorporation of residual stresses into the surface of the tool is beneficial for wear resistance. Refinement of powder processing methods to produce laminated WC-Co tools with a better distribution of cobalt should yield a further increase in machining performance.