Increasing microhardness and hardening depth of grade 2 wheel steel using fiber lasers

This paper considered the existing methods of improving the strength characteristics of railway wheelsets. The technologies of laser and plasma hardening for solving the task of improving wear resistance and contact fatigue strength of railway wheelsets were compared. An in-depth description of the thermal hardening method using multi-kilowatt lasers was given. The properties of the micro-indenters and laser equipment used were presented. The experiments were conducted for the Grade 2 wheel steel. The experiments conducted allowed determining the optimal process parameters for the laser heat treatment of wheel steel. For determining the optimal process parameters, the power, heat treatment speed, laser spot diameter was varied. According to the chosen process parameters, an experiment on surface hardening of Grade 2 wheel steel was conducted. The paper presented the results of measuring microhardness and the depth of hardening for different beam defocusing positions and laser power. The process modes for the heat treatment of the Grade 2 wheel steel were given. The general images of the tracks after microstructure laser hardening, as well as the microstructure images for different processing speeds, were presented. The microstructure of the track itself for images with different magnification ratios and the track boundary between the hardened metal and the main metal were analyzed. Based on the results of the study, the use of fiber laser is recommended for the task of surface hardening of railway wheelsets.