Preparation And Microstructure Mechanical Properties Of Iron Matrix Composites Reinforced By In-situ Carbide Particulate

In this paper carbide particulates reinforced iron-matrix composites were prepared by in-situ synthesis reaction.Ti–Fe,V-Fe,C and steel 20 are the main raw materials used for the synthesis of the composite.The influence of modification and heat treatment on microstructure and mechanical properties were investigated by Optical Microscope,SEM,TEM,XRD,hardness meter and impact tester.The wear resistance of composite was conducted in MM-200 tester.The results showed that modified and unmodified two kinds of composites with carbide volume fraction of 18% were prepared by in-situ reaction casting method.The casting structures of in-situ carbides particles reinforce iron-matrix composites were pearlite,carbide,chrysanthemum graphite and little ferrite before and after modification.After RE modification matrix structure of casting composite was changed from lamellar pearlite and granular pearlit to granular pearlit.The RE modification could change the growth mode of carbide,which made the carbide change from bar shape to regular granular.Whether conducted medication or not the types of carbides were Ti VC2 and VC.The hardness value of composite with modicaton achieved HRC37.1 and impact toughness reached to 2.7J/cm2.Comparing with samples that were not modified hardness value and impact toughness increased by 4.27% and 35% respectively.At different quenching temperatures,the miscrostructures of composite were martensite,carbide and small amounts of retained austenite.The modification could improve the matrix structure of the composites,and the microstructure of the composite was changed from plate martensite to plate martensite and lath martensite.After modification the secondary carbides were fine and content increased.With quenching temperature increase the hardness of modified and unmodified composites decrease gradually and the impact toughness values increase first and then decrease.The impact toughness of the composites reached the maximum after quenching at 920°C.The modification had little effect on the hardness of the composites after heat treatment,but the impact toughness was improved obviously.The impact toughness of the composite was increased from 9.0J/cm2 to 11.2 J/cm2.Quenching at 920°C the fracture type of modified composite was quasi-cleavage fracture.The fracture type of cast was intercrystalline fracture.Under the condition of dry sliding wear,the weight loss and wear rate of the composites increased with the load increasing.The wear resistance of the composites could be improved by RE modification.The wear behaviors of the composites under different loads were different.When the load was less than 600 N,the weight loss increased slowly.When the load was greater than 600 N,the weight loss increased rapidly.Under different loads the wear mechanisms were different.Under low load,the main wear mechanisms were abrasire wear.And the oxidation wear and abrasive wear were the main factors under high load.