Experimental Study on Running-In of Steel Gear Pairs With Micro- and Nano-Materials

First, the paper put forward the method of making running-in oils with micro-quartz or nano-diamond powder. Then, the two oils were applied to the running-in of a gear pair respectively. The gears were made of steel C45E4 and by gear shaping. The tooth surfaces of the involute spur gears are fairly rough and soft. These parameters were measured as following: direct-reading and analytical ferrograph of oil samples, electric resistance between the gear pair, oil temperature, 3D-topography and energy spectrum and scan electron image of the tooth surfaces. The results showed that the running-in wear under the micro-oil is much more severer and unstabler than that under the nano-oil. The nano-particles can adsorb and fill into the tooth surface hollows, which improves the surface properties of the metal teeth. The micro-particles mainly form abrasive wear. The running-in wear mechanism of the gear pair under nano- and micro-oils mainly consists of adhesive, oxidative, sliding and abrasive wears. Furthermore, the electric phenomenon, “negative electric resistance”, happened in the running-in wear of the gear pair.