Author

Xiaonong Qiu

Date

November 1987

Document Type

Thesis

Degree Name

M.S.

Department

Dept. of Materials Science and Engineering

Institution

Oregon Graduate Center

Abstract

In recent years a Japanese head hardened (HH) premium rail steel in North America has experienced rolling contact fatigue (RCF) problems. Field observations suggest that this material exhibits premature surface spalling, however no controlled field experiments have been carried out to support this view. The current work was undertaken on behalf of a major railroad which uses the HH rail steel. The rolling contact fatigue behavior of this and two other rail steels used by the company, namely a standard carbon (STD) rail steel and a second premium rail steel alloyed with chromium and molybdenum (CrMo), was evaluated in laboratory tests. The experiments were conducted using an Amsler wear testing machine under water lubricated, rolling-sliding conditions over a range of contact pressures. It was found that the HH rail steel possesses the best RCF resistance of the three steels. Further, an attempt was made to characterize the fatigue crack appearance and to correlate it to RCF resistance. The results suggest that HE rail steel and CrMo rail steels are superior to STD rail steel in terms of both crack initiation and propagation. Supporting microstructural and mechanical test evaluations show that HH rail steel has the smallest pearlite interlamellar spacing, lowest inclusion content, and the highest tensile strength, ductility, impact resistance and wear resistance. It is therefore concluded that the investigation has revealed no metallurgical deficiency that could explain why HH rail should experience a RCF problem in practice with respect to other rail steels. While it is not possible, from the small number of mechanical tests on only three materials, to draw any firm conclusions about the correlation between RCF resistance, microstructure, and mechanical properties, the data does suggest that RCF resistance correlates directly with tensile strength, and wear resistance.

Identifier

doi:10.6083/M4PG1PPG

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