Experimental Study on Friction Characteristics of Miter Gate Bottom Pivot with Different Solid Lubrication

The miter gates act as an important part of the hydro-junction, and they take into account two functions: shipping and power generation. Their bottom pivots work under low speed and heavy load underwater for a long time, and applying grease as a single lubricant is easy to cause poor lubrication. Practice has proved that friction and wear were important reasons for the failure of the bottom pivot of the miter gate. In order to further extend the maintenance cycle and improve the service life, the gate of the five-level ship lock in the Three Gorges had been lubricated with grease and solid lubricant to reduce friction and wear. Graphite, MoS₂ and PTFE are the three most commonly used solid lubricants in industry. In order to study the effect of these three kinds solid lubricant powder and grease on the tribological performance of the bottom pivot matching pair materials (45 steel and tin bronze), the bottom pivot of the Three Gorges miter gate was taken as the research object, the pin-disk matching pair surface structure was designed according to calculated the maximum contact stress and maximum operating speed, and the filling hole’s size was obtained according to the similarity theory. The three kinds of solid lubricant powder and binder were mixed in a certain proportion to form mixed fillers and fill in the filling holes, and the filler was solidified at 80℃ for 12 hours, and ensured the filler was flush with the disk’s surface. Then the wear test was carried out on the MMW-1A tester after the disk’s surface was coated with grease, and the friction and wear results were analyzed in combination with three-dimensional surface morphology test and ferrography test. The results showed that under the experimental conditions, the friction coefficient of PTFE was the minimum, followed by graphite, and the friction coefficient of MoS₂ was the maximum, and the average friction coefficients were 0.25, 0.18 and 0.09 in one hour, respectively; the wear amount of the disk specimen, average wear depth and wear weight from small to large were graphite, PTFE and MoS₂. Compared with the surface parameters before wear, in addition to the graphite lubrication condition, the surface root mean square value (S_q) and the surface arithmetic average value (S_a) decreased, the other values showed an upward trend. Meantime, under the graphite lubrication condition, the wear form was only single adhesive wear, and under the MoS₂ or PTFE lubrication condition, the wear form were mixed wear formed by adhesive wear and fatigue wear, and the particle sizes of particles produced by graphite lubrication were smaller than that produced by MoS₂ and PTFE lubrication. Therefore, it was considered that graphite was the better solid lubricant among these. On this basis, the continuous wear test for 13 h under graphite lubrication was carried out, the experiment results showed the average friction coefficient and wear mass indicated an overall trend of first decreasing and then increasing with time, which provided a theoretical basis for the solid lubrication design of the bottom pivot friction pair of miter gate.