Lowering friction of ball screws made of different steel grades through ultrasonic impact treatment

Ball screws made of SCM445H, NF42CD4 and SAE4150 steel grades were treated by ultrasonic nanocrystal surface modification (UNSM) technique to boost their performance by improving the surface integrity and lowering the friction. It was found that the friction of the UNSM-treated ball screws reduced successfully thanks to the improvement in surface integrity, transformation of tensile residual stress into compressive residual stress. Suggested mechanisms concerning lowering the friction of ball screws were discussed. Consequently, the feasible possibility of adopting the UNSM technique to a ball screw in order to improve its performance and reliability through lowering the friction was systematically investigated. Accordingly, the application of UNSM technique is a crucial approach to determine the replacement of those three different steel grades.