Tribological Characteristics of High-Chromium Based Multi-Component White Cast Irons

Abstract

It has been evaluated the relationship between the microstructure and three-body abrasive wear behavior of high-chromium (18 and 27 mass % Cr) based (3 mass % each of V, Mo, W, and Co) multicomponent white cast iron materials (high-Cr MWCIs). It was also compared to MWCI to determine the service life of the materials. The results indicate that the microstructure of the material is composed of mainly martensite matrix and different types of precipitated carbides. The wear resistances of both the high-Cr MWCIs are higher than MWCI owing to the higher hardness (4–18% increment in hardness), although they contain fewer carbide types. The carbide volume fraction of high-Cr MWCI increases with increase in the Cr content, but the hardness decreases, leading to a reduction in wear resistance. This is because the transition metal significantly consumes C atoms to form more eutectic carbides during solidification, which is exacerbated by the depletion of C in the matrix during heat treatment to form coarser secondary carbides. This means that increasing the addition of Cr does not always lead to an increase in the hardness or wear resistance of the material. In addition, the wear resistance of 27Cr MWCI after tempering (wear rate: 8.80 × 10−5 g/m) is higher than that after quenching (wear rate: 9.25 × 10−5 g/m) owing to the increase in the fracture toughness of M7C3 carbide. This is contrary to the case of 18Cr-MWCI; the wear resistance after tempering (wear rate: 5.29 × 10−5 g/m) is worse than that after quenching (wear rate: 5.11 × 10−5 g/m) owing to the reduction in hardness as a stress-relieving effect.

Keywords

• abrasive wear
• three-body abrasion
• multicomponent white cast iron
• carbide volume fraction
• fracture toughness
• hardness