Nano mechanical properties of 40Cr surface layer after ultrasonic surface rolling processing

The mechanical properties of 40Cr surface layer after ultrasonic surface rolling processing(USRP) was studied. Nano indentation experiments were used in determining the elastic modulus, nano hardness and residual stress of the surface layer. The test results show that the elastic modulus and hardness of surface layer can be improved significantly after USRP, the maximum values of which under 3 repeated USRP are 217.16, GPa and 3.588, GPa, and 224.8, GPa and 3.857, GPa for 6 repeated USRP, respectively, all of which are located in the surface. Meanwhile, residual compressive stresses are induced in the surface layer with the maximum value located in surface and increasing with the increase of repeated processing times. Contrast experiment results indicate that the number of reciprocating processing times has an important influence on mechanical performance.