Abstract
Nanodiamonds (ND) present a unique combination of desirable mechanical, functional, and chemical characteristics that are ideally suited for reinforcing and enhancing the wear resistance of carbide based materials. Tungsten carbide cobalt (WC-Co) matrix nanocomposites reinforced with varying amounts of ND (2 – 10 vol.%) were synthesized here by spark plasma sintering. The rapid thermal consolidation route enabled attainment of dense samples with a significant retention of the metastable diamond phase. NDs affected the microstructural evolution, chemistry, and mechanical properties of WC-Co. Macroscale reciprocating pin-on-disk tests were conducted to assess wear behavior under conditions relevant to service environments, e.g., high cycles and high contact pressure. Microscale tribological properties were assessed using microscratch tests in order to investigate the intrinsic effects of ND on the localized mechanical and tribological response of WC-Co-ND composites. The incorporation of 10 vol.% ND enhanced wear resistance at both the micro- and macroscale, by 28% and 35%, respectively.
Highlights
WC-Co is a widely used ceramic based material with applications in aircraft breaks, drilling machinery, bearings, and other applications that require high wear and corrosion resistance
Because of its simplicity and the low temperatures utilized, which are ideal for processing the metastable ND phase
The nanocomposite powders were consolidated into bulk form by spark plasma sintering (SPS)
Summary
WC-Co is a widely used ceramic based material with applications in aircraft breaks, drilling machinery, bearings, and other applications that require high wear and corrosion resistance. Conventional approaches to enhancing wear resistance consist of increasing carbide content, at the expense of the ductile Co binder. B4C is utilized because of its low density and its exceptionally high hardness, and has shown promising results in increasing the hardness and wear resistance of spark plasma sintered WC-Co-B4C composites[12,13,14]. NDs are incorporated into WC-Co in order to enhance WC-Co wear resistance by providing both a higher hardness phase, as well as a carbon rich composition that will inhibit dissolution and the associated loss of ductility. Internally in the powder compact via joule heating This technique has been demonstrated to reduce the sintering temperatures and dwell times necessary to consolidate ceramic based materials, while attaining superior properties as compared to conventional sintering routes[18]. A multi-scale approach is taken for evaluating the tribological behavior of the WC-Co-ND nanocomposites in order to distinguish intrinsic localized effects of ND from microstructural changes induced by the variable amounts of ND reinforcement
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