Rolling Contact Fatigue Performances of Carburized and High-C Nanostructured Bainitic Steels.

Yanhui Wang,Zhinan Yang,Fucheng Zhang,Bo Lv,Chunlei Zheng

doi:10.3390/ma9120960

Abstract

In the present work, the nanostructured bainitic microstructures were obtained at the surfaces of a carburized steel and a high-C steel. The rolling contact fatigue (RCF) performances of the two alloy steels with the same volume fraction of undissolved carbide were studied under lubrication. Results show that the RCF life of the carburized nanostructured bainitic steel is superior to that of the high-C nanostructured bainitic steel in spite of the chemical composition, phase constituent, plate thickness of bainitic ferrite, hardness, and residual compressive stress value of the contact surfaces of the two steels under roughly similar conditions. The excellent RCF performance of the carburized nanostructured bainitic steel is mainly attributed to the following reasons: finer carbide dispersion distribution in the top surface, the higher residual compressive stress values in the carburized layer, the deeper residual compressive stress layer, the higher work hardening ability, the larger amount of retained austenite transforming into martensite at the surface and the more stable untransformed retained austenite left in the top surface of the steel.

Highlights

The phase transformation theories, composition design, microstructure characteristics, and conventional mechanical properties of nanostructured bainitic steels have been widely studied by numerous material researchers in the past decade [1,2,3,4,5,6,7,8,9,10]
It can clearly seen that the L10 life of the CC steel is approximately the same with that of the HC steel, but the be clearly seen that the L10 life of the CC steel is approximately the same with that of the HC steel, but the L50 life and characteristic life of the CC steel are 1.4 times and 1.5 times longer than that of the HC steel, respectively
(2) The finer carbides’ dispersion distribution in the top surface, the higher residual compressive stress values in the carburized layer, the deeper residual compressive stress layer, the higher stress values in the carburized layer, the deeper residual compressive stress layer, the higher work-hardening capacity, the larger amount of retained austenite transforming into martensite work-hardening capacity, the larger amount of retained austenite transforming into martensite at the surface and the more stable untransformed retained austenite left in the top surface play at the surface and the more stable untransformed retained austenite left in the top surface play important roles in improving the rolling contact fatigue (RCF) performance of carburized nanostructured bainitic steel

Summary

Introduction

The phase transformation theories, composition design, microstructure characteristics, and conventional mechanical properties of nanostructured bainitic steels have been widely studied by numerous material researchers in the past decade [1,2,3,4,5,6,7,8,9,10]. The extraordinarily fine bainitic ferrite plates are responsible for the excellent strength, and the carbon-enriched retained austenite films account for the high toughness of the nanostructured bainitic steels. Most of these nanostructured bainitic steels are high-carbon (C) and high-silicon (Si) steels [1,2,3,7,8,9].

Methods

Results

Conclusion