Microstructure and mechanical properties of a Mo alloyed high chromium cast iron after different heat treatments

摘要

In the present study, 6 wt% Mo was added into high chromium cast iron (HCCI, 16 wt% Cr), and the effects of heat treatment on microstructure and mechanical properties of the base and alloyed HCCI were investigated. A ledeburite matrix and Mo-rich M2C were obtained besides M7C3 in the as-cast alloyed HCCI. During the soaking process of the destabilization treatment, amounts of secondary carbides (M23C6) precipitated out of austenite. Martenstic transformation of matrix occurred in the forced air cooling process. Most of the M2C decomposed into bright white fishbone M6C and punctate MC. The overall hardness of alloyed HCCI increased due to the presence of Mo-rich carbides and martensite matrix with secondary carbides. Comparing with the destabilized sample, the toughness of the alloyed HCCI improved and the hardness decreased after tempering treatment, and the toughness of the alloyed HCCI increased with the increase of tempering temperature. The abrasive wear resistance of the HCCI improved with the addition of Mo after heat treatment, and the QT500 sample had the optimal wear volume loss. The abrasive wear resistance decreased with the increase of tempering temperature, due to the exsolution of C atoms in the martensitic matrix.