Study On The Fretting Wear Behavior Of MG Alloy And Its Surface Treatment

Fretting is a small amplitude oscillatory movement that occurs between contacting surfaces. Fretting may occur in many engineering key structures, such as space mechanisms, nuclear power plants, electrical equipments, and even orthopaedic implants. Some of the failures initiated by fretting have tragic consequence. With many excellent properties such as low density, the high strength-to-weight ratio and stiffness-to-weight ratio, good machinability, magnesium alloy has been more and more used in many important industrial branches. However, the fretting wear behaviors and mechanism of magnesium alloy and its surface modification have rarely been investigated systemically.The fretting wear experiments were performed by a hydraulic fretting test rig equipped with liquid container and cathode polarization device. The systematic studies have been conducted on the fretting wear behavior of three magnesium alloy(ZM5,MB8,MB15), as well as microarc oxidation modification of ZM5 magnesium alloy and electron beam modification of MB8 magnesium alloy. The fretting wear scars have been carefully characterized through optical microscope, scanning electrical microscope, laser confocal scanning microscope and energy dispersive spectroscope. The main research works and obtained conclusions are listed as following.1. The running condition fretting map of ZM5 alloys were established, the fretting wear behavior of three magnesium alloy were disclosured. In the running condition fretting map, three fretting regimes: partial slip, mixed fretting and slip regime, are clearly separated. Under the stationary normal force , with the increasing the displacement amplitude ZM5 alloy access firstly to the mixed fretting regime, the MB15 access lastly to the mixed fretting regime. In the same regime, the damage behavior of MB15 alloy is lightest, ZM5 alloy is strongly. The steady-state friction coefficient of three magnesium alloys have the most numerical value in the slip regime. 2. In the partial slip regime, the damage behavior of magnesium alloys is slight, the wear mechanisms are the combination of adhesive and slight oxidation wear. In the slip regime, the damage behavior is that the scaling wear pit is covered by a large number of black abrasive dust, the wear mechanisms are the combination of adhesive,oxidation and delamination wear. In the mixed fretting regime, the damage behavior is slight scaling wear or slight adhesive wear, the wear mechanisms perform as abrasive, adhesive and oxidation wear.3. The modified layer thickness of the microarc oxidation modification of ZM5 magnesium alloy and electron beam modification of MB8 magnesium alloy is approximately ten micron, their roughness of surface storngly increase. With the increasing the displacement amplitude, their fretting running regime are form partial slip regime to mixed slip regime to slip regime. Based of the different wear volume of the modification magnesium alloys and bulk material, the wear damage behavior of the modification is more slight. The modification magnesium alloys partly improve the capability against fretting damage in different of fretting running regime.