Study of the Running-In Period in the Twin-Disc Wear Test Using Steel From a Class C Forged Railway Wheel

The railway wheels are one of the most critical components of the train and, any problem that may arise in the wheel, can generate numerous consequences. The ability to manage friction at the wheel-rail interface currently represents one of the greatest challenges and one of the most powerful tools in railway engineering. To define the efficiency of a product for friction control, retentivity tests are performed mainly by the suppliers. However, there is no strict standardization for the tribological test performance, and some critical issues like the influence of running-in period and the necessary superficial conditions of the rolling track to apply the friction control products are neglected. Thus, the objective of this work is to conduct dry twin-disc wear tests with different number of cycles to understand the running-in period and verify the tribosystem behavior. Starting from a rolling track with a polished surface, it was noted that the roughness increased rapidly and stabilized around 1500 cycles. The coefficient of traction (COT) increased at the beginning of the tests reaching the maximum at 750 cycles, reducing the value after that, and stabilizing at a value close to 0.4 with 5000 cycles. Thus, for twin-disc tests using these conditions, it is suggesting the application of friction control products from 5000 cycles because the COT and roughness would be stabilized.