The graphite-MoS2 coated on GCr15 bearing steel is prepared through air spraying and its tribological performances are investigated experimentally. Then its coefficient of friction (COF) and wear scar width (WSW) are investigated through the MFT-5000 multifunction tribometer and other test equipments. The experimental results show that the addition of the graphite can effectively decrease the COF and narrow the WSW of the MoS2. There exists a critical applied load for wearing out the surface with the graphite-MoS2 coating. Moreover, there exists an optimal rotational speed of 500 rpm to decrease the COF and WSW of the GCr15 steel.

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Purpose This study aims to explore the superiority of the compound dimple (e.g. the rectangular-rectangular dimple) and compare its tribological performance for rough parallel surfaces with those of the traditional one-layer dimple (simple dimple). Design/methodology/approach A mixed-lubrication model for a rough textured surface is established and solved using the finite difference method for film pressure and contact pressure. To accelerate the evaluation of surface deformation, the efficient Continuous convolution fast Fourier transform algorithm is applied. The effects of the compound dimple on the tribological performance for the rough parallel surfaces is numerically investigated. And these effects are compared with those of the simple dimple. Furthermore, a reciprocating friction test is conducted to verify the superiority of the compound dimple. Findings The compound dimple exhibits better tribological performances in comparison with the traditional simple dimple, that is, a larger load-carrying capacity and a smaller friction coefficient. To achieve the best tribological performances for the rough parallel surfaces, the depth ratio of the lower pore to the total pore of the compound dimple and the dimple interval should be reasonably chosen. For the surface with compound dimples, there exists an optimal surface roughness to simultaneously maximize the load-carrying capacity and minimize the friction coefficient. The smaller friction coefficient of the surface with compound dimples is verified by the reciprocating friction test. Originality/value The compound dimple is proposed and the superiority of this novel surface texture is confirmed. This study is expected to provide a new texturing method to improve the tribological performances of the traditional simple dimple.

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Purpose -The purpose of this study is to investigate the thermal elastohydrodynamic lubrication (TEHL) analysis of a deep groove ball bearing. Design/methodology/approach -The TEHL model for the groove ball is first established, into which the elastic deformation is incorporated. In doing so, the elastic deformation is solved with the fast Fourier transform (FFT). And the bearing temperature rise is solved by the point heat source integration method. Then, effects of the applied load, relative velocity and the slide-roll ratio on the TEHL of the bearing are analyzed. Findings -There exist the large pressure peaks at two edges of the raceway along its width direction and the increment in the relative velocity between the roller and the raceway, or one in the slide-roll ratio arguments the temperature rise. Originality/value -This study conducts a detailed discussion of the TEHL analysis of deep groove ball bearing and gives a beneficial reference to the design and application of this kind of bearings.