Study on damage mechanism and wear behavior of rail welding joints under controlled kinetic energy

Welded joints are the vulnerable points of seamless steel rails, and their resistance to impact wear is crucial for the safety, stability, and comfort of high-speed trains. However, research on the impact wear behavior of welded joints is limited. This study employed a self-made impact wear tester, utilizing GCr15 balls as a counterpart, to systematically analyze the wear behavior in typical areas of rail welded joints under a controlled impact energy of 25000 mJ. Furthermore, by varying the impact velocities (60 mm/s, 80 mm/s, 100 mm/s, and 120 mm/s), we thoroughly evaluated the effects of material characteristics and impact velocity on wear behavior. The results indicated that the base metal demonstrated the highest resistance to impact wear, while the heat-affected zone exhibited the lowest resistance. Notably, material accumulation was observed at the edges of the impact craters, suggesting significant plastic flow during repeated collisions. In the initial phase of repeated impacts, the size of the impact crater increased rapidly, with plastic deformation being the primary damage mechanism. Once contact stress and yield strength reached equilibrium, the energy absorbed by each collision mainly contributed to crack initiating and propagating. Afterward, the primary damage mechanisms in the welding zone and heat-affected zone shifted to oxidation and fatigue wear. Compared to the rapid increase in wear volume caused by plastic deformation, the rise in wear volume attributed to fatigue wear was minimal.