Both corrosion and abrasion remove materials from some engineering components such as impact coal crusher hammers, pulverizer rings, chute liner, and rolls or molds. Intensive research has been done on improving the wear resistance of high chromium alloys, however, studies into corrosion resistance of high chromium alloys are insufficient. In order to determine the amount of ferroniobium addition in the wire to achieve the best corrosion resistance, and find out the mechanism of ferroniobium enhancing the corrosion resistance of the welding overlays, the high-Cr iron-based welding overlays with different niobium addition were fabricated by using self-made self-shielded metal-cored wires and their acidic corrosion resistance in 3.5 wt.% NaCl solution + 0.01 mol/L HCl solution were investigated by electrochemical corrosion test. The microstructure and corrosion morphology were characterized by OM, SEM, XRD and EDS. The polarization curves and values of I _corr, E _corr and Rc indicate the corrosion resistance is at the highest with 3.6 wt.% niobium addition, and at the lowest when the niobium addition is 10.8 wt.%. The corrosion of welding overlay occurs in the matrix of microstructure. With the increase of niobium addition from 3.6 wt.% to 10.8 wt.%, the proportion of network eutectic structure in the welding overlay is increased. Up to 10.8 wt.%, the microstructure is transformed from hypereutectic structure into eutectic one, leading to a higher acceleration of corrosion rate. When niobium addition reaches 14.4 wt.%, the welding overlay is transformed into a hypoeutectic structure. The addition of niobium element consumes carbon element in the alloy, which makes the increase of chromium content in the final solidified matrix, leading to an improvement in corrosion resistance.

Production of spheroidal graphite cast iron is today quite mastered technology. There are many methods achieving the nodular graphite morphology. Each of these methods have specific characteristics and requirements to technical support, properties and the type of applied modifier. Selection of the spheroidization method is dependent on foundry disposition, production character, economic balance, quality requirements, etc. In case of centrifugally casting the core, which fills body and neck of the roll, is created by ductile iron. Considering the sophisticated production of centrifugally cast rolls for hot rolling mills it is necessary to ensure a high reproducibility and reliability of ductile cast iron production quality in the bulk range of 9-18 t per tapping. These conditions are in the Roll Foundry in Vítkovicke Slevarny, spol. s r.o. provided and verified mastered overpour method and the newly injection of cored wire in the melt.