Research On Surface Texture Processing Of Roller Cone Bit Bearings And Its Influence On Tribological Properties

Cone bit is one of the main oil drilling tools. It is easy to wear under high temperature, low speed, high load and mixed lubrication work conditions, so bearing life has become one of the bottlenecks in the development of cone bit. It has been proved that bionic surface texture is an effective method to improve the tribological behavior of the sliding surface in bad condition, and has been applied in many fields to improve the tribological properties, but there is little literature about the surface texture application in the petroleum equipment ?such as a cone bit sliding bearing? available. This thesis focused on the surface texture machining method on cone bit sliding bearing and its effect on tribological properties, the main results are as follows:?1? Combining the rock bit sliding bearing and the MDW-1 friction and wear tester, an indoor equivalent unit experiment program, pin on disk friction model is applied in, is designed to simulate 81/2" cone bit sliding bearing under 9 tone drilling load. Based on Hertz theory, the equivalent experimental parameters is calculated, the experiment conditions are load:420N, rotation speed:120rpm, temperature:100? and lubricant:Lithium compound grease.?2? JDPMS₈0A precision engraving machine is used to machine surface texture ?300?m-800?m? with three kinds machining path. The bottom morphology and size accuracy of every surface texture is analyzed, the results show that the diameter accuracy was little affected by machine path, when the diameter is larger than 400 ?m, precision engraving method cannot be adopted to machine surface texture. Four specimens with different diameter surface texture are engraved.?3? Surface texture with the diameter 100?m-700?m are fabricated on beryllium specimens by nanosecond laser marking machine. The 3D profile and microstructure on the wall is analyzed. Because of the influence of debris melted by nanosecond laser, this method is not suitable for fabrication surface texture which diameter is not in 200?m-600?m. Four specimens with different diameter surface texture are fabricated with nanosecond laser.?4? A femtosecond laser experimental fig is designed to study the relationship between laser parameters ?power ?0.16W-0.54W?, pulse number ?100-300?? and surface texture character ?ablation diameter and depth?. Due to the laser power and the plasma shielding effect, femtosecond laser ablation method is not suitable to fabricate surface texture if the diameter is larger than 300?m. In addition, a program that fabricating surface texture on disk is designed. And experiment specimens with different is fabricated by femtosecond laser.?5? Wear experiment lasting for 2 hours has been conducted on textured specimens with different parameters which fabricated by various methods and the coefficient of friction ?COF? and wear amount of disk ?WAD? and pin ?WAP? are analyzed. The results shows that surface texture fabricated by precision engraving cannot reduce wear significantly. But with nanosecond laser or femtosecond laser, surface texture proves tribological properties significantly, and femtosecond laser group is little better.In summary, surface texture is innovatively applied into rock bit sliding bearing in this thesis, three surface texture fabricate method has been studied. In addition, the conclusion that surface texture can reduce COF, WAD and WAP, prolong sliding bearing working life has been proved by wear experiment, and we optimized the fabrication method. The research results could make suggestions on the selection of fabrication method and surface texture parameters, with wide application prospect and research value. Moreover, this thesis can make a contribution to improve the rock bit quality and enhance the international competitiveness of high-speed roller bit products.