Resistance to high-temperature oxidation and wear of various ferrous alloys used in rolling mills

Various materials are commonly used to manufacture work rolls for hot rolling mills, such as ICDP (Indefinite Chill Double Pour) cast irons, high-chromium white cast irons and high speed steels (HSS). Various chemical compositions and microstructures are studied in order to optimize the in-use behaviour of those grades of rolls. In this paper, six grades of ferrous alloys (an ICDP cast iron, an ICDP cast iron enriched in vanadium, niobium and molybdenum, a HSS, a graphitic HSS, a high-chromium white cast iron (Hi-Cr), and a niobium-molybdenum-doped high-chromium white cast iron) were investigated. High temperature oxidation tests with gravimetric means at 575°C in water vapour atmosphere and sliding wear tests were carried out. The oxidation kinetics was followed during oxidation test. The microstructure was observed by optical and scanning electron microscopies. The oxides formed on the surface of the samples were analysed by XRD and EDS. The thickness of the oxide scales and the mass gain were measured after oxidation test. The results showed that the behaviour of all the grades differed. The oxide scale of HSS and HSS-G grades was fine and their friction coefficient was low. The weight gain after oxidation test of HSS was high. Hi-Cr and M-Hi-Cr grades presented highly porous oxide layer and an important increase of the friction coefficient during wear test. ICDP and M-ICDP had intermediate behaviour.