Fabrication of in situ Ni(W)-WC nano composites via mechanical alloying and spark plasma sintering

Abstract

Microstructural and mechanical properties of spark plasma sintered Ni-30 wt% W powders fabricated via mechanical alloying (MA) for 48 h were reported in the present study. Due to the intensive WC contamination during MA, the synthesized powders are termed as Ni(W)-WC nanocomposites. The MA'd powders were sintered at temperatures between 800 and 1000 °C via spark plasma sintering (SPS) technique and high density (~97%) Ni(W)-WC composite compacts having high micro hardness values (~4.30 GPa) and high elastic modulus (~270 GPa) were obtained. The effects of sintering temperature, duration and hBN spraying of the graphite die on the phase compositions, i.e. WC content, microstructure and mechanical properties were investigated systematically by using X-ray diffractometer (XRD), Rietveld analyses, scanning electron microscopy (SEM), microhardness and depth-sensing indentation techniques. The crystallite sizes of both the Ni(W) solid solution and the WC phases increased with increasing sintering temperature and durations: An average crystallite size of 39 nm for the Ni(W) solid solution phase in the SPS-800 sample increased to 86 nm for the SPS-1000-5 min sample, likewise, about 14 nm crystallite size of WC phase in the SPS-800 sample increased to 78 nm for the SPS-1000-5 min sample. The SPS-1000-hBN sample had the highest relative density and microhardness values of 97.33% and 4.35 GPa, respectively.