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  • Comparative study of the dr...
    Bolelli, Giovanni; Berger, Lutz-Michael; Bonetti, Matteo; Lusvarghi, Luca

    Wear, 01/2014, Letnik: 309, Številka: 1-2
    Journal Article

    Recent studies of HVOF-sprayed WC–(W,Cr)2C–Ni coatings indicated an applicability at temperatures above 600°C. Therefore, in the present paper the dry sliding wear behaviour of coatings prepared from one selected feedstock powder was studied up to 750°C and compared to a WC–10%Co–4%Cr coating as reference. Coatings were prepared onto stainless steel substrates by a liquid-fueled high velocity oxygen-fuel (HVOF) spray process. A Cr–W–Ni–C “mixed” matrix phase and chromium-rich large (W,Cr)2C grains were formed as a result of metallurgical reactions between the components WC, Cr3C2 and Ni during spraying; therefore, the resulting coating can be better designated as WC–(W,Cr)2C–Ni. The dry unidirectional sliding wear behaviour of the coatings, studied according to ASTM G99 against Al2O3 counterbodies at four different temperatures (25°C, 400°C, 600°C, 750°C) and at two sliding speeds, was interpreted on the basis of their microstructure, micromechanical properties and oxidation behaviour. The morphology and composition inside the wear scars were also studied by SEM and micro-Raman spectroscopy. The results show that the WC–(W,Cr)2C–Ni coating exhibits good wear resistance up to 750°C, whereas WC–CoCr, in spite of its very mild wear at low temperature, suffers from catastrophic oxidation at 750°C. •Reaction mechanisms for the particular WC–20%Cr3C2–7%Ni feedstock powder are proposed.•Sliding wear of WC–(W,Cr)2C–Ni and WC–CoCr HVOF-sprayed coatings studied up to 750°C.•WC–(W,Cr)2C–Ni has mild wear rates increasing gradually up to 10−5mm3/(Nm) at 750°C.•Up to 600°C, harder, tougher WC–CoCr exhibits lower wear rates than WC–(W,Cr)2C–Ni.•At 750°C, WC–(W,Cr)2C–Ni forms a tribofilm whilst WC–CoCr oxidises catastrophically.