| In this thesis, OCrl8Ni9Ti austenitic stainless steel and 16MnR low alloy steel were welded for sampling by manual arc welding respectively, then two kinds of steel welded joints were treated by supersonic particles bombarding(SSPB) to form nano-size grain on the surface, the microstructure of the surface layer of the samples was characterized by means of optical microscope, X-ray diffraction, transmission electron microscope, scan electron microscope, and so on. The results showed that the nanostructured surface layer were fabricated on the surface of two kinds of steel, and gradually increased with the depth. The grain size was 15-25nm at the top surface layer. The microhardness of the samples was measured and compared by microhardness testing mechine from surface to inner. The same hardness can be found for the nanostuctured surface layers of the weld, HAZ and base metal of steel respectively, which was much higher than that of the sample before the SSPB treatment. The tensile and bended properties of samples for two kinds of welded joints by SSPB treated and untreated were compared. Results showed that the tensile property was a little improved and welded joints by SSPB had not an effect on the bended property. Homogenization of facial microstructure of two kinds of steel welded joints were achieved. The compressive stress layer of 200-400um with maximum stress of os induced by SSPB decreased gradually along the depth.The property of sulfide stress corrosion resistance was studied by sustained load tensile test method. Results showed that treated welded joints by SSPB surpassed untreated welded joints. The rupture time of stainless steel was enhanced as many again as, and the rupture time of 16MnR was enhanced twenty-five percent when their stress was lower than bend intensity. To two kinds of steel, resisting stress corrosion property of OCrl8Ni9Ti surpassed IGMnR's. The development mechanism and mechanics property of the surface layer was essentially probed.
|
PDF Full Text Request