Very high cycle fatigue characteristics of a chrome-molybdenum steel treated by ultrasonic nanocrystal surface modification technique

Abstract

Characterization of very high cycle fatigue (VHCF) performance is of significant issue for ensuring long-term durability and reliability of machinery and structural components due to the growing industrial demands and significant requirements of the advanced systems. In this study, VHCF characteristics of nanocrystallized skins (nanoskin) on JIS SCM435 (AISI 4137) steels were investigated as three different nanoskins on the surface, which was fabricated by altering the static load of ultrasonic nanocrystal surface modification (UNSM) treatment. The fatigue characterization, which shows linearly proportional correlation in the range of 80-120 μm depth of subsurface, was subjected to severe plastic deformation by altering the static loads of UNSM treatment to 40, 70 and 100 N, respectively. The fatigue strength increased up to 30% in the regime of VHCF. The improved strength mainly resulted from the generation of nanocrystalline structure, the enhanced surface uniformity, hardness and residual stress. © 2013 Wiley Publishing Ltd.