Experimental Study on Laser Shock Peening and Ultrasonic Surface Rolling Composite Strengthening of Ultra-high Strength Steel
In order to improve the fatigue performance of high load-bearing structural parts of ultra-high strength steel(45CrNiMoVA),a composite strengthening method of laser shock peening and ultrasonic surface rolling(LSP-USR)is proposed.A series of experiments including the composite strengthening of laser shock peening and ultrasonic surface rolling are carried out.The influence of composite strengthening on the surface integrity of ultra-high strength steel is revealed by using SEM,TEM and other detection methods.The results show that composite strengthening can effectively reduce surface roughness.Compared with laser shock peening strengthening and ultrasonic surface rolling strengthening,the roughness decreases by 44.1％and 8.3％respectively,and the finishing effect of ultrasonic surface rolling strengthening plays a key role.The maximum residual compressive stress on the surface layer after composite strengthening can reach-1 274 MPa,which appears within 0.2-0.3 mm from the surface,and the depth of the residual compressive stress affected layer exceeds 1.4 mm.The distribution regularity of residual stress after composite strengthening reflects the superposition of two processes,and the depth of the influence layer of ultrasonic surface rolling strengthening is about 0.5 mm.Within 0.5 mm from the surface,the residual stress distribution is similar to that of a single ultrasonic surface rolling strengthening,while beyond 0.5 mm from the surface,the residual stress distribution is similar to that of a single laser shock peening strengthening.After composite strengthening,the surface material exhibits significant plastic deformation and obvious grain refinement.The effectiveness of the composite strengthening method of laser shock peening and ultrasonic surface rolling is proved,which is of great significance to the development of surface strengthening technology of high load-bearing structural parts of ultra-high strength steel.
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