Effect of externally added Al₂O₃ particles on the microstructure and wear resistance of the working layer of centrifugally cast semi-steel rolls

To address the insufficient wear resistance of traditional centrifugal composite semi-steel rolls, submicron Al₂O₃ particles were introduced into the working layer via master alloy pre-dispersion. Using a ZUB160CrNiMo roll, the radial centrifugal motion trajectories of 0.1–3μm Al₂O₃ particles within the working layer were calculated based on the simulated liquid residence time during centrifugal casting. It shows that nano/submicron particles (< 1 μm) disperse throughout the working layer, while larger ones (≥ 3 μm) segregate at the inner surface. Within the working layer containing Al₂O₃, non-metallic particles mainly exist in the form of Al2O3 or Al2O3-MnS composites. These particles close to the outer-surface region exhibit a smaller average size and greater number density relative to those located near the inner-surface region. With the possible effect of heterogeneous nucleation induced by non-metallic particles, the Al2O3-containing working layer outer surface exhibits a lower degree of Cr, Mo, and Ni segregation than the Al2O3-free one. This subsequently accelerates the fragmentation of network carbides and promotes the precipitation of granular carbides. With the carbide precipitation morphology being improved, the total carbide content increased by approximately 6%, hardness rose by approximately 36 HV, and wear volume decreased by 73%.