Effect of ultrasonic surface rolling on microstructure and rolling contact fatigue behavior of 17Cr2Ni2MoVNb steel

Ultrasonic surface rolling (USR) treatment with different rolling loads (600, 800, 1000 and 1200 N) was introduced to the 17Cr2Ni2MoVNb steel. The microstructure and rolling contact fatigue (RCF) behavior after USR treatment were investigated. Results pointed out that grain refinement existed in the surface-modified layer of the material after USR treatment. The treatment with rolling load at 1200 N could produce a best surface enhancement effect, compared to the untreated sample, the microhardness of USR treated sample (25 kHz, 1200 N) was increased from 795 HV0.2 to 905 HV0.2, with an increase by 13.8%. The surface residual compressive stress was increased from -334 MPa to -527 MPa, with an increase by 57.8%. However, the samples treated at 1200 N increased the surface roughness and caused some surface cracks on the rolled surface, which was an important factor to reduce the fatigue life. The results from RCF tests showed that USR treatment with rolling load at 1000 N exhibited the maximum mean life of 3.71 x 10(6) cycles.