Effects of copper on wear and rolling-sliding contact fatigue of rail steels

The effects of copper content on the wear and rolling contact fatigue (RCF), specifically rolling sliding contact fatigue (RSCF), of hypereutectoid rail steels were evaluated. Steel from three heats of head hardened, hypereutectoid rails with copper levels of 0.07, 0.38, and 0.85 wt pct were selected for the study. All of the material was industrially produced through electric arc steelmaking at EVRAZ, Pueblo. Wear behavior was evaluated through the use of twin disc testing for the three hypereutectoid rail steels. The samples were measured at specific intervals. A high wear rate was observed during the first 1,000 cycles after which a linear steady state wear rate was observed. A small decrease in the steady state wear rate was observed with increasing copper content and increasing strength. Preliminary RSCF testing was performed using the 0.38 wt pct Cu rail steel and an intermediate hardness rail steel to evaluate two RCF testing methods reviewed in literature, a fully lubricated method and a dry-lubricated method where dry cycles were used to initiate damage and the lubrication was added to propagate the cracks through a hydrostatic mechanism. In both cases the 0.38 Cu hypereutectoid material outperformed the intermediate hardness rail steel. The fully lubricated method was chosen for the primary RSCF testing. The primary RSCF testing was performed with the three hypereutectoid rail steels and an intermediate hardness steel as a reference. A longer RSCF life was observed for the hypereutectoid rail than the intermediate hardness, as well as an increase in RSCF life with increasing copper content within the hypereutectoid steels. Atom probe tomography was used to investigate the location of the copper within the hypereutectoid rail steels, and clusters of higher copper concentration within the ferrite at the ferrite/cementite interface were observed.

Name thesis:degree_name

Master of Science (M.S.)

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Metallurgical and Materials Engineering

Grantor dc:publisher

Colorado School of Mines. Arthur Lakes Library

Year dc:date.issued

2017

Author dc:creator

• Froman, Jarred

Advisor dc:contributor.advisor

• De Moor, Emmanuel

Committee members dc:contributor.committeemember

• Matlock, David K.
• Cryderman, Robert

• rail
• wear
• rolling contact fatigue
• copper

Statement dc:rights

• Copyright of the original work is retained by the author.

Language dc:language.iso

eng, English

Identifier

T 8234

OAI identifier oai:identifier

oai:repository.mines.edu:11124/170691