Restoration of Rolling-Contact-Fatigued Surfaces via Nanoskin Technology

Abstract

Rolling contact fatigue (RCF) is known as the dominant factor determining the service life of bearing materials. In this work, the fatigue life of the typical bearing alloy was significantly improved by introducing a nanoskin layer on the surfaces of the test specimens. The nanoskin layer structure was obtained by means of the ultrasonic nanocrystal surface modification (UNSM) technology. The microstructure of the nanoskin was analyzed via scanning electron microscope (SEM), electron back-scatter diffraction (EBSD), and transmission electron microscope (TEM). SUJ2 and SUJ3 bearings at different states of fatigue were subjected to UNSM treatment. For SUJ2 a rotary-bending fatigue (RBF) life average for three untreated specimens was chosen as 100% life, and then several untreated specimens were fatigued to 25%, 50% and 75% of life with subsequent UNSM treatment. This way used bearing conditions were simulated. The rotary-bending fatigue (RBF) tests of fatigue+UNSM SUJ2 specimens have shown 377-430% improvement of fatigue life, comparing to untreated specimens. For SUJ3 a RCF life untreated specimen was chosen as 100% life, and then several specimens were fatigued to approximately 100% of surface damage with subsequent UNSM treatment. Thus damaged surface conditions were simulated. The RCF tests of fatigue+UNSM SUJ3 specimens have shown 218% improvement of fatigue life, comparing to untreated specimens. This indicates the possibility of the restoration of the RCF life of bearing alloys by means of nanoskin treatment via UNSM technology.

Bearings Downsizing by Strength Enhancement and Service Life Extension

“…These high dense and intense cycles pressure induces a high cycle of severe plastic deformation (SPD) up to a certain depth and high cycle of elastic deformation beneath this depth. The changes in mechanical properties and performance by UNSM treatment of a bearing alloy steel have been reported earlier [ 12 ]. In order to validate a possible reduction in the size and weight of slim bearings by adapting a UNSM technology, the increase in RCF strength needs to be examined using the experimental test specimens made of SAE52100 first, and a typical standard bearing can be selected to justify the effects in the same way on real standard bearings.…”

Effect of Ultrasonic Nanocrytalline Surface Modification on Hardness and Microstructural Evolution of Cu-Sn Alloy

“…Shot peening is an effective way of introducing compressive stress on surface of the materials, which enhances hardness, corrosion resistance, and retards crack nucleation and propagation resulting in expanded fatigue life [4]. Ultrasonic nanocrystalline surface modification (UNSM) is a new developed technique, which facilitates the surface properties and microstructure to extend the fatigue life, hardness, wear, corrosion resistance, and improve a better surface tomography [5,6]. Our previous investigations have shown that the effective grain refinement was introduced by the UNSM due to plastic deformation into steel [7,8], Al and Ni-based alloys [9,10].…”

“…Experimental set up UNSM treatment. Figure 1 is a schematic of the UNSM technique, detailed set-up of which has been reported elsewhere [5][6][7][8][9][10]. The surface is worked with a WC ball that is mounted on a transducer, which vibrates at a high frequency perpendicular to the surface (z-direction), with potential of 2 dimensional (x, y) control.…”