Effects of Molybdenum Addition on Rolling Contact Fatigue of Locomotive Wheels under Rolling-Sliding Condition.

Yanpeng Wang,Xuehua Liu,Qiang Zou,Wenjian Wang,Haohao Ding,Pengcheng Xiang,Jun Guo,Qiyue Liu

doi:10.3390/ma13194282

Abstract

Rolling contact fatigue (RCF) damages often occur, sometimes even leading to shelling on locomotive wheel treads. In this work, the RCF damage behaviors of two locomotive wheel materials with different molybdenum (Mo) contents were studied, and the influence of depth of wheel material was explored as well. The result indicates that with the increase in the Mo content from 0.01 wt.% (wheel 1, i.e., a standard wheel) to 0.04 wt.% (wheel 2, i.e., an improved wheel), the proeutectoid ferrite content and the interlamellar spacing of pearlite decreased, the depth and length of the RCF cracks increased and the average RCF live of locomotive wheel steel improved by 34.06%. With the increase in the depth of material, the proeutectoid ferrite content and the interlamellar spacing of pearlite increased, the depth of RCF cracks increased, the length of RCF cracks of wheel 1 increased and then decreased whereas that of wheel 2 decreased, the RCF live showed a decrease trend for wheel 1, while the RCF life increased and then decreased for wheel 2. The processes of shelling can be divided into three patterns: cracks propagating back to the surface, crack connection and fragments of surface materials.

Highlights

Rolling contact fatigue (RCF) has played an important role in determining the operational reliability of the wheel/rail system [1]
Mo content could lead to obvious differences in the microstructures, the proeutectoid ferrite content and the interlamellar spacing of pearlite (ISoP)
By comparing the subsurface damage around the shelling of two kinds of wheels, we found that the main differences between wheel 1 and wheel 2 were: (i) the size and quantity of cracks in wheel 2 were smaller than those in wheel 1; (ii) there was milder fragment damage of materials near the surface in wheel 2 than in wheel 1

Summary

Introduction

Rolling contact fatigue (RCF) has played an important role in determining the operational reliability of the wheel/rail system [1]. Residual stresses and strain hardening occurred in the material near the wheel/rail contact after cyclic loading, which raised the elastic limit for wheel materials. This phenomenon was called elastic shakedown [2,3]. When the stress in the contact exceeded the elastic shakedown limit of wheel materials, permanent plastic deformation occurred for each subsequent wheel revolution. Once the material ductility was not sufficient to satisfy the accumulated deformation, the RCF cracks eventually began and grew. This phenomenon was called ratchetting [2,3]

Results

Discussion

Conclusion