硼酸镁晶须增强镁基复合材料的摩擦性能及磨损行为

Tribological properties and wear behavior of Mg_2B_2O_(5w)/AZ91D magnesium alloy matrix composites

研究真空气压渗流法制备的硼酸镁晶须增强镁基复合材料(体积分数30%)及其基体合金在液体石蜡润滑条件下的滑动摩擦磨损性能。试验条件为滑动距离2km,滑动速度0.5、1.0、2.0、3.0和5.0m/s,载荷5、10、18、25和40N。结果表明:在润滑条件下,引入增强相MgB2O5能提高复合材料在低载下的耐磨性能。随着载荷的增加,复合材料的磨损由轻微磨损向严重磨损转变。临界载荷分别为:1m/s,25N;2m/s,18N;3m/s,10N;5m/s,5N。复合材料磨损情况的扫描电子显微分析和观察显示,复合材料在两种摩损阶段的主导磨损机制分别为磨粒和剥层磨损。研究还发现,复合材料由轻微磨损阶段向严重磨损阶段的转变不仅与载荷有关,还与滑动速度有关。

The liquid Paraffin-lubricated sliding tribological properties and wear behavior of Mg2B2O5 whisker reinforced magnesium matrix composites fabricated by vacuum-gas pressure infiltration process were investigated by using a pin-on-disc wear-testing machine against a GCr15 steel counterface under loads of 5-40 N, and within a sliding velocity range of 0.5-5.0 m/s for a constant sliding distance of 2 km. The results show that the transition load is found for a constant sliding velocity. When the loads are higher than the transition load, the wear rate increases sharply. The composites exhibit superior wear resistance compared with that of matrix alloy when the loads are below the transition load. The transition loads that are called critical loads in some literatures are 25, 18, 10 and 5 N for velocities of 1, 2, 3 and 5 m/s, respectively. The abrasive and delamination wear mechanisms are the dominant ones for loads above and below critical loads according to the SEM analysis of the worn surfaces and the subsurface of the composites. The crossover from abrasive wear mechanism to delamination wear mechanism of the composite is related not only with the loads but also with the sliding speeds.