| The structure of material has direct effect on its usages. People put forward many methods of surface performance improvement to meet the demands of working conditions. Comparing with traditional surface performance improvement technic, ultrasonic surface processing is a convenient, high efficiency and low cost technology. Nanostructured layers were fabricated on the metal machines and parts by ultrasonic processing, as well as geometrical modality nanocrystallization was formed, so the surface performance was advanced.In this paper, the samples of 45 steel, 40Cr steel and aluminum alloy were processed by TJU-UMSNT-â… ultrasonic surface nanocrystallization device, which is made in Welding institute in Tianjin University. Observe microstructure on the treated sample by Transmission Electron Microscope, determine the roughness on the treated sample by high precision inductance type roughometer, analyze the relation between the hardness and distance from surface on the treated sample by micro-sclerometer and analyze abrasion degree on the samples treated before and after by Scanning Electron Microscope.Results are as follow:(1) Equiaxed crystal nanostructured surface layers were fabricated on 45 steel, 40Cr steel and aluminum alloy by ultrasonic processing. The grain orientation takes on random distribution, at the same time, high-density dislocation tangle is formed and the grain is highly refined.(2) The surface roughness is significantly reduced of 45 steel and 40Cr steel after ultrasonic processing, smooth surface comes into being and the surface quality is obviously improved.(3) The surface hardness of 45 steel and 40Cr steel highly increased after ultrasonic surface processing, comparing with the center of the samples. Hardness falls as the distance to the surface increases.(4) After ultrasonic processing, friction factor is smaller than original sample of 40Cr, wearing capacity is reduced and surface resistance to abrasion is enhanced.
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