牙轮钻头轴承单元试件的摩擦磨损性能

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Because of the small structure size, high working load and temperature, and poor lubrication condition, the main failure of rock bit bearing is caused by friction and wear. In order to improve the bearing lubrication performance and service life, the mathematical model of fluid lubrication of rock bit bearing was built through simulating the working condi- tions of rock bit bearing units, and the variations of friction coefficient, wear capacity and temperature of rock bit bearing unit specimens under different conditions were studied on MMW-1 universal testing friction and wear machine with bearing materials of 20CrNiMo as pin and beryllium bronze as disc. The results show that, on the simulated operating conditions of rock bit bearing, the friction coefficient of the pin-disc specimens is increased as the load increasing at constant rotation speed, and reduced as the rotation speed increasing at constant load. The temperatures of the specimens and the grease are increased with the increase of load and speed, and at the load of 120 -200 N and the speed of 60 - 192 r/rain, the tem- peratures of the specimens and the grease maintain at a lower value of about 40 ~C , that is a better lubrication performance is got. The wear surface morphology analysis shows that the adhesive wear results in the failure of rock bit bearing.由于牙轮钻头轴承的结构尺寸小、工作载荷大、温度高、润滑条件差等，导致其失效主要为摩擦磨损。为了提高轴承的润滑性能和使用寿命，模拟牙轮钻头轴承单元工况，建立其流体润滑的数学模型；分别以牙轮钻头轴承单元材料20CrNiMo和铍青铜为销和盘，在MMW-1型万能摩擦磨损试验机上研究不同工况下试件的摩擦因数、磨损量及温度变化。结果表明：在牙轮钻头轴承模拟工况下，当转速一定时，试件的摩擦因数随载荷的增大而增大，当载荷一定时，摩擦因数随着转速升高而逐渐降低；试件及润滑脂的温度随载荷和转速的升高而升高，当载荷为120～200N、转速为60～192r／min时，试件的温度保持在40℃左右较低的温度，即润滑性能较好。磨损表面形貌分析表明，牙轮钻头轴承的失效形式为黏着磨损。