| Al2O3/W-Cr composites have good corrosion resistance,wear resistance and thermal stability,are one of the best materials to replace H13 steel hot extrusion die.The size and interfacial bonding of the reinforced particles Al2O3 have a direct impact on the properties of the composites.However,there is almost no research on the regulation of the size and dispersion of Al2O3 particles at home and abroad.Therefore,this paper has studied these issues.In this paper,Al2O3/W-Cr composites were prepared by sol-gel autogenous powder metallurgy method.The effects of Cr on Al2O3/W heterointerface interface and the diffusion behavior of Cr in W and Al2O3 were investigated by diffusion couple test.The friction and wear properties and wear mechanism of composite materials at room temperature were studied.The density,flexural strength and hardness of the composites were tested by Archimedes drainage method,electronic universal testing machine and Rockwell hardness tester.The microstructure,chemical composition and wear surface of the composites were observed by SEM and EDS.The main conclusions of this paper are as follows:(1)With the increase of PEG content or milling time,the average particle size of the reinforcing particles Al2O3 in the composites decreases first and then increases,and the density and hardness first increase and then decrease.The effect of mechanical milling on the refinement of Al2O3 particles is more significant.When the milling time is 15h,the Al2O3 particles in the composite material are uniformly dispersed.The average particle size of Al2O3 is 0.45μm,the hardness can reach 72.4HRC,and the density is as high as 99.96%.(2)In the Al2O3/W-Cr composite,the granulated Al2O3 is decomposed by Al(OH)3 prepared by the sol-gel method during hot-pressing;Cr element acts as a joint in the composite.The interface between Al2O3 and tungsten-chromium substrate is metallurgical.(3)By studying the diffusion kinetics of Cr in W and Al2O3,it is concluded that Cr diffuses into W is bulk diffusion control,while Cr diffuses into Al2O3 is interfacial diffusion control.The flexural strength of composite increases with the increase of sintering temperature and holding time.When the sintering temperature is 1550 C and the holding time is 2h,bending strength reaches the maximum value of 11.25 MPa;Fracture always occurs at the interface of Cr-Al2O3,Microstructure is mainly composed of smooth polygonal and rough pleated areas,and the area of the pleated area increases with the increase of sintering temperature and holding time.(4)The friction coefficient and wear rate of Al2O3/W-Cr composites decrease with the decrease of average particle size of Al2O3.With the increase of load,the friction coefficient of composite increases first and then decreases,and the wear rate is constantly increasing.When the average particle size of Al2O3 is large or the load is low,wear mechanism of the material is mainly abrasive wear;as the average particle size of Al2O3 decreases and the load increases,wear mechanism becomes adhesive wear,at the same time accompanied by abrasive wear. |
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