Selective Laser Sintering Preparation and Tribological Testing of Nanostructured Tungsten Carbide-Cobalt Composites

This paper describes the results to date of research done to compare and contrast the tribological properties ofnanostructured tungsten carbide-cobalt composites consolidated by selective laser sintering (SLS) and conventional grain size composites of the same chemical composition consolidated by conventional commercial methods. The powder preprocessing and selective laser sintering methods will briefly be described. The tribological testing methods will be discussed, and the tribological properties of the selective laser sintered and commercially consolidated materials will be compared. It will be seen that the nanosized WC-Co composites have far superior harness and wear resistance compared to their microsized counterparts. Introduction It has long been known that by refining the grain size ofpolycrystalline materials you can greatly improve many of their mechanical properties. Nanostructuring seeks to carry this principle out to its ultimate extreme by producing polycrystalline materials with grains, say, one hundred atoms in diameter. The problem with these materials is that they are produced in powder form and conventional consolidations methods can't be used because they involve long exposure to high temperatures which cause rapid grain growth and destroy the nanostructuring. This is where SLS comes into play. The consolidation rate is so rapid with SLS that the nanocrystals don't have time to grow. This paper will first describe the powder preprocessing steps to densify the nanostructured WC-15Co powder* prior to sintering. Next, the SLS parameters will briefly be discussed, and, finally, the microhardness and abrasive wear resistance of the SLS nanostructured WC-15Co will be compared to those of the commercial WC-15Co. * Supplied by Nanodyne Incorporated, New Brunswick, N. J.