Abstract
Reasons are considered for unsatisfactory operation of the energy-absorbing device of railway wagon drawbar, whose main element is a friction plate with special energy-absorbing cermet coating. The main specifications for the friction plate are resistance to shock loads, resistance to thermal cycles in the temperature range from ambient temperature to 850–870°C, good resistance to shear stresses, friction coefficient stability in this temperature range, lack of seizure to friction wedge material made of steel, and long operating life up to 10,000 loading cycles. According to results of metallographic studies using optical and scanning electron microscopy with energy dispersion microanalysis it is established that the poor quality of the friction plate metal composite coating is caused by the following factors: localization of eutectic containing sulfur, iron, and manganese along the “ceramic-substrate” boundary, and presence of oxide films on the surface of precursor powder particles. As a result of this excess interfaces arise in cermet material that are areas of microcrack formation during cermet operation. Thermal stresses arising during metal composite briquette manufacture lead to crack development at the interface of metal composite and a steel base. Application of unevenness to the steel base of metal composite material in a hydrogen or endogas atmosphere makes it possible to avoid both thermal cracks and subsequent metal composite separation during operation. An improvement in operating characteristics is confirmed during laboratory tests under conditions approximating operational.
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