July 1996

Document Type


Degree Name



Dept. of Materials Science and Engineering


Oregon Graduate Institute of Science & Technology


The railroad industry has historically sought improvements in rail lubrication techniques. The Association of American Railroads (AAR) has sponsored research into novel solutions to this problem. Plasma sprayed coatings were thought to show promise as a lubricant reservoir or as a vehicle to produce a self-lubricating coating. A high carbon steel coating was to be developed that would withstand the high slide/roll ratios and loading conditions seen at the wheel/rail interface. A 1080 steel was selected because of its similarity to the composition of rail steel. A literature review, concentrated on plasma generation and particle behavior in the plasma jet, was made. Substrate preparation techniques were researched and a protocol established that assured an acceptable bond, which is largely mechanical, between coating and substrate. Single splat analysis, a technique for predicting coating quality, was developed. Plasma spray parameters and techniques were optimized using the single splat analysis method. Backside cooling, a substrate cooling method, was initiated. N2 and H2, were used as primary and secondary gases. Coatings were sprayed onto Amsler rollers and tested on an Amsler wear test machine. Up to 35% slide/roll and 1220 MPa contact pressures, dry and lubricated, were used to test coating performance. Wear rates for coatings were significantly lower than uncoated rollers. The spray parameter envelope was established by the likelihood of debonding rather than by a fall off in wear performance. Two debonding mechanisms were identified and techniques implemented for their control. Reliability of the process in producing coatings that would consistently yield good wear performance was proven. The goal of developing a plasma sprayed 1080 steel coating that would withstand the rigors of laboratory test was met.





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