Effect of Heat Treatment on Microstructure and Mechanical Properties of Ti-alloyed Hypereutectic High Chromium Cast Iron

摘要

The effect of heat treatment on the microstructure and mechanical properties of Ti-alloyed hypereutectic High Chromium Cast Iron (HCCI) containing Fe-17 mass%Cr-4 mass%C-1.5 mass%Ti was investigated. The size distribution and the volume fraction of carbides (M_7C_3 and TiC) as well as the matrix structure (martensite) were examined by means of scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). It was found that the number of fine secondary M_7C_3 carbides with a size below 1 μm increases with lower holding temperatures and shorter holding times during heat treatment. The number of coarse primary M_7C_3 carbides with a size above 11.2 μm increases with increasing holding temperatures and longer holding times. In addition, the number of TiC carbides increases with increasing holding times, and martensite units are more refined at longer holding times and lower holding temperatures, respectively. Moreover, the volume fraction of martensite increases with increased holding times. In conclusion, low holding temperatures close to the eutectic temperature and long holding times are the best heat treatment strategies in order to improve wear resistance and hardness of Ti-alloyed hypereutectic HCCI.