Comparative analysis of wear properties between electroless Ni-B coating and commercial ZnAl coating on 38Si7 steel used in railway system

With the advancement of railway infrastructures, one significant challenge encountered within fastening systems is the degradation of tension clamps, which compromises the structural integrity between the rail and its base. Although galvanization has been implemented as a remedial measure, it has not yielded satisfactory performance, prompting ongoing research to enhance these components. This study aims to improve the mechanical and wear properties of 38Si7 steel tension clamps utilized in railway tracks through the application of electroless NiB coating. For this purpose, three distinct sample categories were analyzed: non-coated 38Si7 steel, ZnAl-coated 38Si7 tension clamp, and NiB coated 38Si7 tension clamp. Comprehensive examinations of their microstructures, phase compositions, hardness, and wear properties were conducted utilizing optical and SEM analyses, XRD, microhardness testing, and ball-on-disk wear testing. The findings revealed a significant enhancement in the surface hardness of the NiB coated specimens, registering at 650 HV, in stark contrast to the ZnAl-coated specimens at 140 HV. Furthermore, the NiB-coated sample demonstrated an increase in wear resistance by more than 15-fold. Consequently, the application of NiB coating on the tension clamps has shown a substantial improvement in their mechanical properties, indicating a promising solution to the existing limitations faced by railway fastening systems.