Laminated WC-CO composites for tribological applications

Laminated WC-Co cutting tools were fabricated with residual thermoelastic stress states tailored to counteract the thermal and mechanical stresses imposed by machining. The weight fraction of cobalt in the tool was graded to produce compressive stresses in the tool surface. Spark plasma sintering (SPS) was used to densify the laminates. Submicron and nanograin powders were used, though the nanograin tools had sintered grain sizes that were similar to the submicron tools. Microstructural analysis showed that the cobalt binder was not well distributed around the WC grains. Contiguity of the WC grains was higher than that of tools sintered by other methods, and pools of cobalt were apparent. The laminated tools performed similarly to commercially available tools in taming Ti-6Al-4V alloy. Performance of the laminated tools may have been hindered by the poor distribution of the cobalt binder. Refinements in powder processing methods are underway to produce tools sintered by SPS that outperform those currently available.