Experimental Investigation on the Wear and Damage Characteristics of Machined Wheel/Rail Materials under Dry Rolling-Sliding Condition

Abstract

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.

Experimental Investigation on the Wear and Damage Behaviors of Machined Wheel-Rail Materials under Dry Sliding Conditions

“…The worn surface morphology of the wheel/rail samples under tribological pairs #C1-#G1, #C2-#G1 and #C3-#G1 is presented in Figure 11 , from which it can be observed that there are discrepancies on the worn surface damage morphologies among the rail blocks and wheel rings. By and large, more serious worn surface damage of the rail blocks can be observed, which is different from the experimental results under dry rolling-sliding conditions reported in our previous work [ 22 ]. Under the dry rolling-sliding condition, the surface damage of the wheel samples is more serious than that of the rail samples.…”

“…It can be seen from Figure 8 and Figure 9 that the surface microhardness of the wheel rings and rail blocks increases remarkably after sliding. In addition, the surface microhardness of the rail blocks is larger than that of the wheel rings before and after the sliding test, which is similar to the phenomenon under the dry rolling-sliding condition reported in [ 22 ]. The surface microhardness of the wheel rings prior to sliding falls in between 324.48 and 356.72 HV 0.1 , and it ranges from 437.34 to 501.09 HV 0.1 after sliding.…”

“…Within the deformation region, the wheel/rail metallographic microstructures are extended and refined along the sliding direction, and eventually the subsurface fibrous layer takes shape. According to the thickness of the SPDL of wheel/rail samples under dry rolling-sliding condition reported in our previous work [ 22 ], the thickness of the SPDL of the wheel samples after the rolling-sliding test ranges from 50 to 60 µm, while the thickness of the SPDL of the rail specimens is greater than 85 µm. In this current study, the thickness of the SPDL of the wheel rings falls in between 28 and 37 µm, while the thickness of the SPDL the rail blocks ranges from 21 to 42 µm.…”

“…The experimentally-employed rail material (Chinese brand: U71Mn, manufactured by Pangang Group Panzhihua Steel & Vanadium Co., Ltd., Panzhihua, Sichuan, China) is a kind of Mn-steel made from high carbon steel to possess high fatigue toughness, which is extensively utilized in current Chinese railway network [ 24 ]. The experimentally-utilized wheel material (Chinese brand: CL60, which was manufactured by Maanshan Iron & Steel Co., Ltd., Maanshan, Anhui, China) is one of the commonly-employed solid forged Mn-steels in current Chinese railway network [ 22 ]. Table 1 presents the chemical constituents of the studied materials.…”

“…As a matter of fact, the surface integrity of the workpiece after machining directly influences the tribological behavior during sliding. In our previous work, we conducted a systematic investigation on the rolling-sliding wear behaviors of machined wheel/rail materials, and we found that the rail material displays better anti-wear properties and that a thicker SPDL of the rail samples was formed [ 22 , 23 ].…”