Lang Yu’s research while affiliated with South China University of Technology and other places

Rail grinding and wheel turning can effectively remove surface defects and unevenness, which is a crucial process for the safe and smooth operation of trains. Machined surface integrity of wheel/rail materials significantly influences their tribological property. In this study, firstly, the rail blocks were ground via a cylindrical grinding machine, and the wheel rings were turned by a computer numerical control (CNC) lathe with varied parameters. Then, the sliding wear and damage characteristics of the machined wheel/rail samples under dry conditions were studied by virtue of a block-on-ring tribometer. The results show that the surface microhardness of the ground rail blocks is larger than that of wheel rings, while the surface roughness and the thickness of the subsurface plastic deformation layer (SPDL) of rail blocks are much smaller than those of wheel rings. After sliding, the surface microhardness of wheel/rail samples increases remarkably. The thickness of the SPDL, the wear loss, and the increase degree of surface microhardness of rail blocks are larger than those of wheel rings. Surface microhardness, roughness and the SPDL of the machined wheel/rail samples impose a combined influence on the anti-wear property, and the tribological pair with proper initial surface roughness and microhardness engenders the smallest amount of total wear loss.

To guarantee the smooth operation of trains, rail grinding and wheel turning are necessary practices to remove surface defects. Surface integrity of machined wheel/rail materials is significant to affect their tribological performance. In this paper, firstly, the wheel specimens were turned by a CNC lathe and the rail specimens were ground by a cylindrical grinding machine with various machining parameters. Then, the wear and damage behavior of the machined wheel/rail discs was systematically investigated via a twin-disc wear testing apparatus under dry rolling-sliding condition. The experimental results show that the surface hardness of rail discs after machining is slightly higher than that of wheel discs, while the surface roughness and plastic deformation layer of wheel discs are much larger than those of rail discs. The surface hardness increase degree of rail discs and their thickness of plastic deformation layer are greater than those of wheel discs after the rolling-sliding test. The wear loss of wheel discs is much larger than that of rail discs. Surface roughness, hardness and plastic deformation layer of wheel/rail discs after machining exert a comprehensive effect on the wear behavior, and friction pair with appropriate original surface hardness and roughness generates the smallest amount of wear loss.

The machined surface integrity of heavy-haul freight wheel is one of the direct factors which affects the wheel’s service performance and life. Based on the wheel turning parameters, single-factor experiments on D840 wheel material under dry cutting condition were performed. The changing laws including the surface work hardening, surface microstructure, surface roughness, and surface morphology were analyzed via micro-hardness tester, metallographic microscope, SEM and surface profilometer under different cutting parameters. The results show that the surface hardness and the hardening layer increase with the increase of feed and cutting depth within a certain range of cutting parameters. The surface amorphous layer and fiber layer thicken with the increase of feed and cutting depth. The fibrosis of proeutectoid ferrite in the plastic deformation layer and the extrusion deformation of the flake pearlite are obvious. Meanwhile, pearlitic lamellar spacing decreases gradually. The surface roughness increases with the increase of feed, and cutting speed a cutting depth have less effect on roughness.