Microstructure And Properties Of (Al₂O_3f+Cr₃C_2p)/Fe Composites

Compared with traditional alloys,ceramic reinforced iron matrix composites have drawn much attention due to their excellent comprehensive properties,such as high specific strength,specific stiffness,high heat resistance and wear resistance.In order to solve the problem of uneven distribution of the ceramic reinforcements in the iron matrix,a foam preform with Al₂O₃ fiber and Cr₃C₂ particles with different volume fractions was prepared,and（Al2O3f+Cr3C2p）/Fe composite and slurry pump volute castings were prepared by lost foam casting,and the effects of Al₂O₃ fiber and Cr₃C₂ particle volume fraction on the microstructure,mechanical properties and wear resistance of the composite were studied.The Matlab statistical software was used to calculate the average dispersion coefficient of different volume fractions of Al₂O₃ fiber and Cr₃C₂ particle reinforcement in the composite,which was used to characterize the uniformity of the distribution of ceramic reinforcement in the composite.It is found that with the increase of the volume fraction of Al₂O₃ fiber and Cr₃C₂ particles,the average dispersion coefficient of the reinforcement at different positions in the composite test block shows a trend of first decreasing and then increasing from the top to the bottom of the test block,among which the average dispersion coefficient at the bottom of the test block is the largest,the top is second,and the middle part is the smallest,that is,the distribution uniformity of the reinforcement in the middle of the composite test block is better,and the bottom and top are poor.When the volume fraction of Cr₃C₂ particles was fixed and the volume fraction of Al₂O₃ fiber was less than or equal to 4 vol.%,the average dispersion coefficient of the reinforcement at different positions of the composite was small,and the changing trend was relatively stable,and the uniformity of the distribution of the reinforcement was better.When the volume fraction of Al₂O₃ fiber increased to 5 vol.%,the average dispersion coefficient of the reinforcement at different positions of the composite increased significantly,the change trend fluctuated greatly,and the uniformity of the distribution of the reinforcement was poor.With the increase of Al₂O₃ fiber and Cr₃C₂ particle volume fraction,the hardness,wear resistance and impact toughness of the composite showed a trend of first increasing and then decreasing,when the volume fraction of Al₂O₃ fiber was 4 vol.%,and the volume fraction of Cr₃C₂ particles was 2 vol.%,the hardness of the composite was 62.12 HRC,the relative wear resistance was 1.58 and the impact toughness was 3.5 J/cm²,which were 11.41%,58%and 25%higher than the high chromium cast iron matrix,respectively.The addition of Al₂O₃ fiber and Cr₃C₂ particles can promote the recrystallization nucleation of the composite,inhibit the growth of the grain,thereby refine the structure of the composite and refine the grain of the composite.In the impact fracture of Al₂O₃ fiber and Cr₃C₂ particle synergistically reinforced iron matrix composite,there are a large number of cleavage steps,river patterns and a small number of secondary cracks,which are manifested as cleavage fracture mechanism,which belongs to brittle fracture.The erosion and wear mechanism of composite materials is mainly micrographic cutting and fatigue spalling.