Microstructural and Mechanical Properties Examination of High-Power Diode Laser-Treated R260 Grade Rail Steels Under Different Processing Temperatures

Abstract

In the present study, high-power diode laser surface treatment was implemented to R260 grade steel with three different processing temperatures (1100 degrees C, 1200 degrees C, and 1300 degrees C) at the laser power of 1750W and scanning speed of 6mm/s, in order to identify the effect of various processing temperatures on the mechanical performance. According to the test results, the laser-treated sample at 1300 degrees C showed much better mechanical performance among the other laser-treated samples. It was found that the laser-treated sample at 1300 degrees C had about 3 times more surface hardness, a 43 pct increase in yield strength, and a 53 pct increase in toughness value compared to the untreated sample. Microstructural investigations showed that this surface treatment did not only generate a martensitic structure with a certain depth but also provided the formation of a fine pearlitic structure contributing to an increase in the mechanical properties. As a conclusion, it was found that the processing temperature is one of the critical factors affecting the mechanical properties in the laser hardening process. Moreover, the results demonstrated that this treatment method might be an alternative method to enhance the mechanical properties of existing rail steels online without the need for rail disassembly, reducing operational costs.