The Experiment And Microstructure Analysis Of Hypereutectic HCCIs Composite Hammer

Nowadays, the hammer crusher has some problems like low wear resistance, low hardness and low toughness etc. It can’t meet the requirement of actual production. Therefore, the service life of hammer crusher will be limited. In this study, we select hypereutectic HCCIs as wear part which has good wear-resisting performance and carbon steel as toughness part which has good toughness, to produce hypereutectic HCCIs-carbon steel bimetal composite hammer using the dual fluid pouring method (First pouring carbon steel and later pouring hypereutectic HCCIs). Compare with hypereutectic and eutectic HCCIs, hypereutectic HCCIs have more content of carbon and chrome, Therefore it has higher volume fraction of primary carbides, and the hardness and wear resistance are higher than those of hypoeutectic and eutectic HCCIs. However, the coarser and larger primary carbides will be precipitated during the solidification of the hypereutectic alloy. The coarser primary carbides are not good to improve the wear resistance of alloy.In this study, we designed a reasonable alloy composition. By means of the different mould to obtain different cooling rate, the influence of cooling rate on microstructure of the hypereutectic HCCIs were examined. In addition, the effect of different pouring temperature on the primary carbide in the hypereutectic HCCIs was discussed. The change of the microstructure of the hypereutectic HCCIs in bimetal hammer, which made with different molds, was studied by optical microscopy. At last, through different pouring temperature and interface temperature, the effect of pouring temperature and interface temperature on microstructure of the hypereutectic HCCIs and the compound interface of the bimetal composite hammer were discussed.The primary M7C3carbide in hypereutectic HCCIs is significant refined with increasing cooling rate. Meanwhile, the shape of primary M7C3type carbides changes from stripe to hexagonal. The number of primary M7C3is increased and distribution of primary M7C3is relative-uniformity. With this cooling range, the primary carbides were refined, and also the hardness and the wear resistance were improved. The equivalent diameter of primary carbide is about6.7μm after refined by increasing cooling rate. In addition, the hardness of hypereutectic HCCI reached HRC54.5with highest cooling rate. However, the primary M7C3carbide in hypereutectic HCCIs is not big change with pouring temperature increase.From the results of the optical microscopy, SEM and macro hardness, it is found that the good metallurgical combination of the bimetal hammer under experimental conditions of interface temperature of1370℃-1420℃and pouring temperature of1450℃-1500℃can be realized. Moreover, the interface place do not have inclusion and porosity, and the thickness of combination layer is about20-30μm.