Dilution effects on microstructure and wear resistance of a Fe-C-Cr-Mo hardfacing alloy

Hardfacing is the application of a hard, wear-resistant material to the surface of a component to reduce loss of material by abrasion, impact, erosion and corrosion. Fe-based alloys containing high amount of carbide-forming elements can be utilized like as-cast products or as hardfacing alloys for producing thick deposits. The main industrial application fields of hardfacing alloys are mining and mineral processing, cement industry and polymer extrusion. Suitable deposition processes are welding-based techniques (e.g. Tungsten Inert Gas deposition, Plasma Transferred Arc), laser cladding or spin casting of the molten alloy inside barrels. The chemical composition of the hardfacing alloys has to be tuned considering the dilution effects with the substrate. In fact, the diffusion of interstitial elements at the deposition temperature is not negligible. In the present paper, the effects of dilution on a hypereutectic Fe-C-B based alloy containing Cr and Mo was investi- , gated. The microstructural evolution was studied by XRD (X-ray diffraction), differential scanning calorimetry (DSC), optical microscopy (OM) and scanning electron microscopy (SEM), while mechanical behaviour was analysed by hardness measurements and wear resistance by pin-on disc tests. The dilution on the reference alloy was simulated by producing laboratory castings with an increased amount of Fe, up to 50 wt. %. For Fe addition higher than 30 wt. % the microstructure shifted from a fully hypereutectic to an hypoeutectic structure with notable differences in alloy properties. In correspondence of the eutectic structure the ; solidification range reached a minimum value. Moreover, the hardness and wear properties of the diluted alloys decreased when the Fe level increased over 30 wt%. ; The obtained results were compared in a first step with the dilution of the hardfacing alloy cast on steel substrates and secondly with the inlay microstructure produced by a real industrial process. In particular the Fe-C-B-Cr-Mo hardfacing alloy produced by the spin casting process showed a dilution level higher than 30 %. Considering that the deposition parameters can highly influence the final microstructure of the inlay, the methodological analysis of the dilution can represent an useful instrument for the quality and the property optimization of the hardfacing alloys.