Effects of ultrasonic impact treatment on surface residual stress and electrochemical properties of 42CrMo4 steel
DONG Zheng
YANG Cong
GU Bangping
YANG Yuchen
GAO Liqiang
XU Guanhua
Abstract：[Objective]To solve the problems that 42CrMo4 steel(commonly used in mechanical components bearing dynamic loads)has reduced service life due to residual tensile stress and is susceptible to corrosion in harsh environments,the regulatory effect of ultrasonic impact treatment on its surface residual stress and electrochemical properties was investigated.[Methods]Firstly,42CrMo4 steel samples were treated with ultrasonic impact for 0,4,and 8 minutes(current 2.0 A,frequency 40 kHz).Secondly,their microstructures were characterized by a ultra-depth-of-field 3D digital microscope,and their microhardness was tested by a microhardness tester.Then,their residual stress was measured by the small hole method.Finally,their electrochemical properties(polarization curves,impedance spectra)were tested using a three-electrode system(3.5%NaCl solution).[Results]The results showed that ultrasonic impact caused plastic deformation and grain refinement on the surface of the samples;at 8 minutes,the average surface hardness reached 262.9 HV(14.3%higher than the initial value),the residual tensile stress was converted to compressive stress and increased with treatment time,and the maximum residual compressive stresses in the x and y axes at 8 minutes were-204.2 MPa and-121.5 MPa,respectively;at 8 minutes,the corrosion current density was reduced to 12%of that of the untreated sample,showing the best corrosion resistance.The synergistic effect of grain refinement,plastic deformation and residual compressive stress was the key mechanism for performance improvement.
Keywords：Ultrasonic impact treatmentMicrostructureMicrohardnessResidual stressElectrochemistry
Publication Date：2026-01-31
Online Publishing Date：2026-09-12(First online date of this platform, not the publication date of the document)
Pages：7( 93-99 )