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Purpose The purpose of this paper is to reveal the influence of dimples on the tribological properties of the “washers-cage-rollers” system of rolling element bearing (REB) under starved lubrication. Design/methodology/approach A fiber laser marking system was used to prepare dimples patterns on the raceways of the shaft washers of cylindrical roller thrust bearings (CRTBs). The friction and wear properties of dimples textured CRTBs with different diameter of dimples (200 µm, 250 µm, 300 µm) and depth of dimples (4 µm, 8 µm, 12 µm) were researched through a vertical universal wear test rig using a customized tribo-pair under starved lubrication. The surface stresses and the influence mechanism of dimple units on the tribological behavior of REBs were also compared and discussed. Findings Although the surface stresses on the raceways of dimples textured bearings are significantly higher than that of the smooth group, the coefficients of friction and wear losses of them are all reduced under starved lubrication. When the effective volume of dimples is between 1.13 and 2.25 and the depth of dimples is smaller than 12 µm, the tribological properties of dimples textured CRTBs are significantly improved. In this work, when the diameter of dimples is 250 µm, and the depth of dimples is 8 µm, the textured bearings can provide the excellent friction-reduction ability and outstanding wear resistance. Originality/value This work is a valuable reference for the raceway design and optimization of REBs.

The 35Cr45Ni steel with the high service temperature of about 1150°C was wildly used in ethylene pyrolysis device. However, the structure of 35Cr45Ni steel will change greatly after it was in service for a long time at high temperature. Therefore, in this paper, focusing on the 35Cr45Ni furnace tubes with different service time (0 and 6 years, i.e. original sample and failed sample), the microscopic morphology and elemental composition analysis were carried out to determine its failure behaviour. The results showed that the fracture morphology of the failed tube was mainly characterized by intergranular cracking, and there were carbides on the local surface of the crack, which was brittle cracking at low temperature. The precipitated phase in original 35Cr45Ni steel was mainly austenitic, M7C3 carbide and MC carbides. In a long-time service at 1000°C, the transformation of M7C3→M23C5 and MC(NbC)→Nb3Ni2Si occurred, and dispersed secondary M23C6 carbide was precipitated in the grain. Additionally, The NbC→Nb3Ni2Si transformation promoted the M7C3 to M23C5 process and the carbide precipitation as well as coarsening.

To explore the effect of dents on the tribological behavior of the “washers-cage-rollers” system of rolling element bearings (REBs), the friction and wear properties of dents textured thrust cylindrical roller bearings (81107TN) with different diameters of dents (DAOD, 200, 250, 300 μm), depth of dents (DPOD, 4, 8, 12 μm) as well as circumferential interval angle (CFIA, 1.5°, 2.0°, 2.5°) were researched under dry wear. The surface stresses of REBs and the influence mechanism of dents were also compared and discussed. The results show that: due to the nylon film formed and left on the raceways, the coefficients of friction (COFs) of dents textured bearings are all higher than the average COF of smooth ones, while their wear losses may become higher or lower, depending on the combination of pattern parameters. The influence of the DPOD on the tribological performance of textured bearings is more significant than that of the DAOD. The results show that, when the DAOD and DPOD are 250 and 8 μm, respectively, compared with the smooth ones, the mass losses of bearings can be reduced by up to 49.22% under dry wear, which would be an important reference for the optimal design of the “washers-cage-rollers” system of REBs.