Effect of trace Ni on the resistance of high-Cr cast iron to slurry erosion

Abstract

High-concentration chromium cast irons (HCCI) are widely used in the oil sands industry for slurry handling. The high resistance of HCCI to slurry erosion is attributed to its combination of hard carbides M7C3 and Cr-containing ferrous matrix. The former withstands the wearing force while the latter helps absorb impact energy and accommodate deformation, leading to high resistance to erosion. The high-concentration chromium generates strong passivation capability, providing the material with high resistance to erosion in corrosive environments. Efforts are continuously made to further improve HCCIs to resist erosion-corrosion. Herein, we demonstrate that the resistance of a HCCI, Fe-35%Cr-3%C, to slurry erosion can be considerably improved by adding trace Ni. Through microstructure analysis with SEM, EDX and XRD as well as first-principles calculations, we demonstrate that the beneficial effect of the trace Ni is mainly attributed to the microstructure refinement due to promoted nucleation of M7C3 carbides. The added Ni atoms decrease the carbide/matrix interfacial energy, thus lowering the activation energy for carbide nucleation leading to increased nucleation rate.