Effect of load and carbide orientation on abrasive wear resistance of white cast iron

In this study, white cast iron with 7.39% Cr was casted into an exothermic mold on a copper chill plate to solidify unidirectionally. The microstructure is composed of oriented M3C carbides and ledeburitic matrix. The specimens were cut both parallel and transversally to the billet axe and pin-abrasion tests were carried out using fixed alumina abrasive grains at loads between 2 and 15 N. The microhardness, elastic modulus and fracture toughness were determined using an indentation technique on transversal and longitudinal directions. The abrasion resistance was correlated with the carbides microhardness and fracture toughness. The M3C carbides showed similar values of fracture toughness in both directions. The carbides in transversal direction showed higher hardness and elastic modulus than longitudinal carbides. The results reveal that for lower loads the mass loss is similar in both directions. However, for loads higher than 10 N the M3C carbides in the transversal direction show higher abrasion resistance than longitudinal carbides. The wear surface was examined by scanning electron microscopy for identifying the wear micromechanisms. Bending and slip planes on longitudinal cementite were observed at 15 N.