Examination of the sliding wear of bronze coatings on railway buffer heads

Abstract

In this study, results of aluminum bronze coatings (CuAl9Fe3) and manganese bronze coatings (CuMn11Al8Fe3Ni3) deposited on specimens made of S355J2 steel using the laser cladding method are presented. This research was carried out to learn the wear mechanisms and tribological parameters of the analyzed bronze coatings in terms of their applicability for railway buffer heads, instead of covering the latter with graphite grease, which entails several disadvantages. It was found that the laser cladding method allows obtaining durable coatings of aluminum bronze (CuAl9Fe3) and manganese bronze (CuMn11Al8Fe3Ni3) on a substrate made from S355J2 steel. Microscopic examination performed after laser cladding of the above described bronzes showed the presence of three zones: the coating, the heat affected zone, and the substrate. The CuMn11Al8Fe3Ni3 manganese bronze coating was characterized by a significantly higher hardness (236.9 HV) than in the case of the CuAl9Fe3 aluminum bronze (181.5 HV). Based on the obtained results, it was found that aluminum bronze coatings had higher wear resistance in comparison to manganese bronze coatings, which may be associated with a higher fraction of Cu2O and Al2O3 phases. The results obtained indicate that the use of a CuAl9Fe3 coating allows for a significant reduction of sliding wear compared to uncoated samples (average wear was reduced by approx. 89.36%), while the use of graphite lubricant allows for an average wear reduction of ca. 91.35%. SEM examination of the specimen surfaces coated with aluminum and manganese bronze showed visible signs of scratching, plowing and micro-cutting, which proves the sliding nature of the specimen wear.