Wear and microstructure of eutectoid steels.

摘要

The interaction between a railroad vehicle wheel flange and the gauge face of the rail causes incredible amounts of material displacement and loss creating significant economic and safety ramifications for railroads. At the same time, inter-modal competition has reduced margins for profit, which in turn has promoted the use of higher tonnage vehicles. The final result is ever increasing rail deterioration rates as present rail metallurgical technology is pushed to its limits. To aggravate the problem, there is no simple method of evaluating potential rail steels for possible revenue use.;A complete range of pearlitic eutectoid microstructures was produced with isothermal heat treatments and their relative wear resistances ranked with the laboratory test procedure. Microstructures were judged based on pearlite interlamellar spacing, hardness and tensile strength. Relative wear resistances were judged according to deformation and wear characteristics.;The wheel flange/gauge face wear mechanism was identified as one of third body abrasion, with the abrasive particles being rail and wheel debris carried into the contact zone, after being generated from previous encounters.;It was found that for the range of interlamellar spacings and hardnesses tested, 118 to 472 nm and 322 to 205 BHN respectively, both wear resistance and deformation resistance increased with reducing spacing. Wear rate/spacing relationships were developed based on the data generated. In addition it was confirmed that interlamellar spacing and hardness are closely related.;Several laboratory test procedures with two machines (Amsler twin disk and a pin-on-disk) were evaluated as simulations of the wheel flange/gauge face wear system. Test conditions involved non-lubricated, steel-on-steel, sliding and sliding/rolling wear. Based on relative wear rates, surface damage mechanisms and surface topographical features, the Amsler machine produced the best simulation with test conditions of high contact pressure and a high slide/roll ratio. The laboratory results were compared to accurately documented performances of four rail steels in trials conducted at the Transportation Test Center Facility for Accelerated Service Testing.