Microstructure and Property Evolutions of Q345B Steel during Ultrasonic Shot Peening

In this paper, the surface of Q345B steel was strengthened using ultrasonic shot peening (USP) technology. Through the adjustment of USP time, power and distance, the surface morphology, roughness and microhardness of the USPed samples were measured using scanning electron microscopy (SEM), energy dispersive analysis (EDS), a roughmeter and a microhardness tester. At the same time, the corrosion behavior of USPed samples was observed and analyzed using software simulation calculation and an immersion experiment on the dynamic polarization curve. Through tests and characterization, the influence of different USP process parameters on Q345B steel and the relationship between them were explored. The original intention of this research was to obtain better parameters to improve both the strength and corrosion resistance of the material. The results indicated that, with the increase in the USP time and power and the decrease in the USP distance, the surface roughness, the thickness of the deformed layer and the microhardness of the samples increased at first and then stabilized, and an obvious delamination phenomenon and chemical composition difference appeared between the deformed layer and the substrate. It was shown that a longer USP time and a shorter USP distance caused spalling and cracks on a substrate surface, resulting in the corrosion becoming more serious. However, with the increase in the USP power, the corrosion resistance of the sample improved