Effect of chromium-induced (Fe, Cr)3C toughness improvement on the two-body abrasive wear behaviors of white cast iron

Abstract

An as-cast chromium white cast iron alloy with chromium (Cr) content of 0 wt%, 1 wt%, 2 wt%, 3 wt%, and 4 wt% was prepared via metallurgical smelting and casting processes. The effects of Cr content on the toughness, hardness, and microstructure of (Fe, Cr)3C carbides was evaluated. The results revealed that the microstructure of the as-cast alloys is mainly composed of bulk carbide and the pearlite matrix. The carbide in the alloy without added Cr, i.e., eutectic Fe3C, was characterized by a continuous network structure. With the addition of Cr atoms, the Fe3C-type carbide was transformed into (Fe, Cr)3C, leading to a gradual increase in the fracture toughness of the carbide. This may have resulted from the incorporation of Cr into Fe3C and the consequent crystal-structure transformation of the carbide. When the Cr content of the carbide was lower than the saturation level (<2 wt%), the microhardness of the carbide in the as-cast alloy increased significantly. This resulted from an increase in the number of strong (Fe–Cr) metallic bonds in the carbide. However, for Cr content exceeding 2 wt%, the microhardness increased only slightly. Changes in the mechanical properties of the carbides resulted in improved wear resistance of the materials and changes in the wear mechanism of the carbides. At low Cr content, the wear failure of the carbide was characterized mainly by brittle fracture and peeling. With improvement in the toughening performance, microcutting became the main wear failure mechanism of the carbides and exerted a significant blocking effect on the silicon oxide abrasive.