Studies On Heat Treatment And Composite Infiltrating Casting Process Of High Chromium Cast Iron

In this paper,the wearable glasses board of slurry pump is studied.Considering its special working environment,in order to enhance its corrosion resistance and wear resistance,Ultra-high chromium alloy cast iron is usually used as the raw material to manufacture this kind of materials.Heat treatment results shows that at the same tempering temperature,the hardness of casting increased at first and then decreased with the increase of quenching temperature,and the hardness reaches the maximum at 1010℃ quenching.At the same quenching temperature,the hardness of casting is also increased at first and then decreased with the increase of tempering temperature,the hardness of casting reaches the maximum at 450℃ tempering.The best heat treatment process parameter is comprehensive determined: 1010℃quenching temperature and 450℃tempering temperature.The average hardness of the heat treated material reached 65.9HRC and impact toughness value reached 4.6J/cm~2.Compared to the cast sample,the macro hardness increased 25% and the impact toughness increased 53%.Comprehensive mechanical properties improved obviously.The microstructure and fracture morphology of the materials before and after heat treatment were analyzed.The chemical composition analysis of the eutectic carbides and secondary carbides which exist in the micro organization is made.It can be known that the eutectic carbides in the cast state are the mixing mechanism of carbide M7C3 and M23C6,after the heat treatment,the metal matrix will disperse and precipitate secondary carbides,the chemical composition analysis shows that the carbide type is M7C3,the specific chemical formula is(Fe2Cr5)C3.The friction and wear tests show that with the best heat treatment process,the comprehensive wear resistance of the material is best,the relative wear resistance of the material is 1.42 times as much as the cast state,which indicate that the trend of wear resistance of the material and the hardness is consistent.Finally,the wear morphology shows that the wear mechanism of the materials before and after heat treatment is micro cutting of abrasive grains.The wear resistance of the material is improved to some extent after heat treatment,but still not ideal.So,in this study,ceramic particles were used to further enhance the wear resistance of high chromium cast iron,the preparation method is the EPC negative pressure casting infiltration,and the surface of ceramic particles is pretreated with nickel plating to improve its wetting effect with the molten iron.The temperature of molten iron is 1520 ℃,the negative pressure is 0.05 MPa,successfully prepared F20,F12 and F6 three different particle size complex material with ceramic particles and high chromium cast iron.SEM and EDS analysis showed that the pretreatment of the ceramic particles is beneficial to the infiltration of molten iron,its effect is equivalent to the addition of alloying elements to high chromium cast iron near the interface of the composite,and the enrichment of the alloying elements in this region makes the surface tension and solid-liquid interfacial tension decreased.So,composite interface combined closely,gradation is distinct.In addition,the mechanism of casting infiltration was analyzed,and the composite casting was quenched at 1010℃ tempered at 450℃.The changes of composite interface after heat treatment were studied.Friction and wear tests show that the relative wear resistance of the cast composite sample is 1.93 times as much as the cast pure metal,the relative abrasion resistance of the composite sample after heat treatment is 2.21 times as much as the pure metal sample.Indicating that pure metal heat treatment process can still be applied to composite materials,it can also improve overall wear resistance of composite materials obviously.Finally,the wear morphology showed that the wear mechanism of the composites is still micro cutting of abrasive grains.