High Temperature Dry Tribological Behavior of Nb-Microalloyed Bearing Steel 100Cr6.

Yucheng Zhu,Chaolei Zhang,Jian Li,Huan Wang,Wenjun Wang

doi:10.3390/ma14185216

Abstract

100Cr6 steel is one of the most widely used bearing steels and a representative of first-generation bearing steel. Many engineering applications require rolling bearings to run at a high temperature. Therefore, it is necessary to improve the high temperature properties of 100Cr6 steel. In this paper, the effect of Nb on high temperature dry tribological behavior, including worn surface and friction coefficient, was analyzed by a wear test when Nb content was 0.018% and 0.040%. The results show that the microstructure is refined gradually, the hardness is improved, and wear volume decreases by 31.8% at most with the increase of Nb content. At 50 °C, the friction coefficient of 100Cr6 steel can be reduced by adding a small amount of Nb, but this effect will be weakened if the content of Nb is too high. In addition, excess Nb increases the hard precipitation of NbC, which aggravates the abrasive wear and leads to the increase in the depth of the worn surface. At 125 °C, the effect of Nb on tribological properties is weaker. With the increase of temperature, the steel substrate softens, and the oxide particles increase, which aggravates the abrasive wear and oxidation wear and makes the wear volume increase significantly.

Highlights

First-generation bearing steel is mainly composed of high carbon chromium bearing steel and is still the most widely used
The results show that the wear mechanism changed when the temperature went up from 50 ◦ C to 125 ◦ C
The results show that the addition of Nb can decrease the friction coefficient of bearing steel at 50 ◦ C

Summary

Introduction

Bearing steel has been developed for four generations, it is not a process of the new replacing the old, but a development process of gradually enriched varieties and gradual subdivision of the application field [1,2,3]. First-generation bearing steel is mainly composed of high carbon chromium bearing steel and is still the most widely used. Taking the world’s largest bearing producer as an example, China’s annual demand for bearing steel is about 3.7 million tons [4], and 100Cr6 and 100CrMn6 are still the main varieties, accounting for more than 95% of the total. The existence of sliding friction inevitably causes wear of bearing parts [5].

Methods

Results

Conclusion