Tribology characteristics of ex-situ and in-situ tungsten carbide particles reinforced iron matrix composites produced by spark plasma sintering

In this paper, ex-situ (adding the particles reinforcement phase into the matrix materials directly) and in-situ (the particles were synthesized directly from elemental powders of W and C during the fabrication) tungsten carbide particle reinforced iron matrix (WC/Fe) composites were well fabricated by spark plasma sintering (SPS) with the particle volume fraction of approximately 30%. The main phases were ferrite, WC, W2C, Fe3W3C and pearlite. The content of Fe3W3C in ex-situ WC/Fe composites was much higher than that in in-situ WC/Fe composites, and some of which spread throughout particles in ex-situ WC/Fe composites. The homogenous distribution of WC particles within the iron matrix was obtained with strong bonding to the matrix. The mean WC grain size was about 24 μm and 13 μm for ex-situ and in-situ WC/Fe composites, respectively. Compared with the traditional martensitic wear-resistant steels, these two type composites presented the more excellent wear resistance which was enhanced at least six times. Moreover, due to the better particles size and interfacial microstructure, the in-situ composite had the lower specific wear rate (2.5 × 10−5 mm3/Nm) which was about 65% to that of the ex-situ composite (3.8 × 10−5 mm3/Nm). The dominant wear mechanism for the in-situ and ex-situ WC/Fe composites was a combination of abrasive wear and oxidation wear, which was different from the micro-ploughing mechanism of the martensitic wear-resistant steel. For the ex-situ composites, coarse-grained WC and higher content of brittle phase Fe3W3C increased the wear rate and reduced the wear-resistance.