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Bearing steel is essential for the driving parts of the rotating body, but fisheye crack of inclusions such as TiN, Al₂O₃ and Cr matrix is formed in the very-high-cycle fatigue (VHCF) regime. Therefore, research on the development of a clean bearing steel that reduces the size of inclusion such as TiN or that does not contain inclusion has been made recently. In this study, the results of long-term attempts by the maker to improve the performance and quality of bearing steel for very long life were quantitatively analyzed from the viewpoint of fracture mechanics. In other words, the phase transformation properties, VHCF characteristics with ultrasonic nanocrystal surface modification (UNSM) treatment and fracture mechanics analysis of this clean bearing are compared quantitatively with those of other common bearing steels from the viewpoint of engineering and industrial applications. The quenching and tempering (QT) specimens of the clean bearing showed fisheye cracks and duplex $S$–$N$ curves in the VHCF regime. The fisheye crack of the clean bearing steel was an internal fatigue crack caused by a small inclusion mainly composed of Al₂O₃ in the VHCF region. However, fisheye cracking due to TiN and Cr matrix, which was observed in other common bearing steels, did not occur in the clean bearing steel due to the efforts of the developers of new clean bearing.

Laser ablation is a rapid-material removal technique with potential application in remanufacturing of bearings to clean damaged surfaces. This study reports the ablation morphology and change in surface composition of 52100 bearing steel irradiated with a femtosecond laser. A smooth ablated surface was achieved by operating the laser at fluence just above the ablation threshold, but higher fluences resulted in roughened surfaces with recast formation. Such coarse morphology is believed to result from higher energy deposition and surface melting. Minimal oxidation occurred at lower fluences. Periodic ripple patterns formed in the ablated area at low fluence; their morphology and possible formation mechanism is discussed.

The effects of aluminum addition on the microstructure and mechanical properties of ultrahigh carbon steel (UHCS) after quenching and tempering were studied in this paper. The results showed that the addition of aluminum significantly enhanced the hardness and temperature resistance. The main reason was attributed to that the addition of aluminum inhibited the transformation of ε-carbide to cementite during tempering and thus resulted in the very high hardness during higher temperature tempering. And with increasing the aluminum content up to 6 %, the carbide network was completely disappeared because increasing addition of aluminum increased the eutectic carbon content significantly. This study not only demonstrated the effects of aluminum on the carbide network but revealed the extra high hardness of the ultrahigh carbon steel alloyed with aluminum, which provided a useful way to develop low density and high hardness bearing steel materials.

Gleeble-3800 thermo-simulation system was used to study the effect of cooling rate on transformation of GCr15steel. The dynamic CCT diagram was established, microstructure and hardness of experimental specimens were analyzed. As the cooling rate lower than 5°C.s-1, the transformed microstructure is composed of pearlite colony and proeutectoid carbide precipitated on the grain boundary. The starting and finishing transformation temperature gradually decreased with the cooling rate increasing. Under higher cooling rate, partial austenite transformed to martensite as temperature lower than 187°C. Vickers hardness increases obviously with cooling rate increasing, which can be explained by the following reasons. The diameter of pearlite colony and the pearlite lamellar spacing becomes smaller at lower cooling rate, and martensite and retained austenite appears at higher cooling rate.