Evaluation of laser cladding as an in-situ repair method on rail steel

Laser clad coatings have been considered as an in-situ repair method to extend the lifespan of rail. Building on previous research which predominantly focuses on the application of such coatings on full sections of rail this study considers repairs of size comparable to the contact patch with the additional consideration of the interface between parent rail and repair at the surface. The small size of repairs relative to previously explored application of full surface claddings necessitated a new investigation of the best performing materials combinations. To enable the evaluation of in-situ repairs a set of experiments were designed to assess multiple repair sites in single tests. Rolling-sliding twin-disc tests were conducted using bespoke rail discs manufactured from standard R260 grade rail steel with six wire eroded slots of varying sizes filled with three different candidate cladding materials, Stellite 6, MSS and R260 powder. The evolution of the surface was monitored through visual observation every 5,000 cycles during the tests, the discs were then sectioned to assess the integrity of the repair and effect of rolling contact loading. During the tests the repair material underwent plastic flow in the direction of traction, experiencing material flow alongside the parent rail steel. The success of laser clad coating as a repair is shown to be dependent on selecting a material which tends to strain by similar amounts to the parent material, making it less vulnerable to crack initiation points forming at the trailing edge where the parent rail may otherwise flow over the repair.