Improvement of Friction and Wear Characteristics for Advanced Al-Si Alloy Matrix Composites

在干湿氩气、氮气、空气和氧气环境下，对Al-Si合金浸渍石墨复合材料与轴承钢接触的无润滑销盘式磨损进行了试验研究。研究了在轴承钢滑动表面形成的粘附膜的性能，并对复合材料的摩擦磨损特性进行了分析。该复合材料的耐磨性和摩擦性能均优于基体（Al-Si合金和石墨），具有湿度依赖性，表明复合材料的组成改善了材料的摩擦学特性。在试验开始后，在轴承钢的滑动表面产生粘附膜，并作为有效的固体润滑膜，特别是在湿气体中。石墨粉中Al-Si合金磨损颗粒的混合促进了压滑增厚作用下薄膜的形成。在潮湿的气体环境中，随着氧气的减少，形成了更多的对比膜，有助于提高复合材料的耐磨性。销举，即负磨损发生在湿气初始阶段，随后随着销举高度的增加，磨损降低。为了寻找与Al-Si合金浸渍石墨滑动接触的良好配合材料，进行了销盘式磨损试验，获得了摩擦磨损最小的材料组合。与自身接触的复合材料产生低摩擦和磨损，表明最佳的材料组合。与复合材料接触的黑色金属如低碳钢、铸铁、轴承钢和商用推力轴承表现出低摩擦和中等水平的磨损率，表现出更好的材料组合。与基体接触的复合材料产生中等水平的摩擦和磨损，显示出不良的组合。钛与复合材料接触带来高摩擦和磨损，导致组合不充分。石墨、铜、黄铜和钛与复合材料接触会导致自身磨损，导致滑动表面最不合适的组合。采用发动机基础油对Al-Si合金浸渍石墨复合材料及其基体（销）与轴承钢（盘）接触进行了单向滑动磨损试验，研究了试验前仅采用浸没润滑和滴油润滑两种润滑方式下的摩擦学特性。在复合销的情况下，随着油滴量的增加，摩擦系数和磨损率达到浸入试验的值。即使油滴非常小，也不会发生油膜的破裂。对于Al-Si合金引脚，油膜击穿的滑动距离随油滴量的增加而增加。在油膜破裂前，摩擦系数波动较大，但几乎不发生磨损，随后摩擦磨损迅速增加。对于石墨销，油滴进给时的摩擦系数和磨损率均低于浸没进给，但磨损率与油滴量无关。这些结果表明，即使在恶劣的润滑条件下，与基体相比，复合材料也是一种良好的滑动材料。少

Unlubricated pin-on-disk type wear tests of an Al-Si alloy impregnated graphite composite in contact with a bearing steel were conducted in dry and wet gas environments of argon, nitrogen, air and oxygen. The properties of an adhered film generated on the sliding surface of the bearing steel were investigated and then friction and wear characteristics of the composite were elucidated. The composite, having a humidity dependency, exhibits wear resistance and friction performance better than the matrices (Al-Si alloy and graphite) in wet gases, indicating that the improvement of tribological characteristics has been made by composing the matrices. The adhered film is generated on the sliding surface of the bearing steel just after the start of the tests and serves as an effective solid lubricating film, especially in wet gases. The mixture of Al-Si alloy wear particles in graphite powder promotes the formation of the films under press-slide fattening action. More compared films are gener … More ated with decreasing oxygen in the wet gas environment and contribute to the improvement of wear resistance of the composite. Pin lifting i.e. negative wear takes place in wet gases during the initial stage and subsequently lower wear occurs with increasing pin lifting height.In order to investigate the good mating materials in sliding contact with the Al-Si alloy impregnated graphite, pin-and-disk type wear tests were conducted and the material combination showing minimum friction and wear was obtained. The composite in contact with itself yields low friction and wear, indicating the best material combination. Ferrous metals such as mild steel, cast iron, bearing steel and commercial thrust bearing in contact with the composite exhibit low friction and middle levels of wear rate, showing better material combinations. The composite in contact with its matrices gives the middle levels of friction and wear, showing bad combinations. Titanium in contact with the composite brings about high friction and wear, resulting in an inadequate combination. Graphite, copper, brass and titanium in contact with the composite causes wear damage to themselves, leading to the most inadequate combinations for sliding surfaces.Unidirectional sliding wear tests of the Al-Si alloy impregnated graphite composite and it matrices (pin) in contact with the bearing steel (disk) were conducted using engine base oil to investigate the tribological characteristics under the lubrication methods of immersion feed or oil-drop feed only before the tests. In the case of the composite pin, as the amount of oil drop is increased, the friction coefficient and wear rate reach the values for the immersion test. The breakdown of oil film does not occur even with very small amount of oil-drop. For the Al-Si alloy pin, the sliding distance to the breakdown of an oil film tends to increase with the amount of oil drop. The wear scarcely occurs but the friction coefficient fluctuates greatly before the oil film breakdown and afterwards the friction and wear rapidity increase. In the case of the graphite pin, the friction coefficient and wear rate under oil-drop feed are lower than those under the immersion feed but the wear rate does not change irrespective of the amount of oil drop. These results suggest that the composite is one of the good sliding materials even under severe lubricating conditions compared with the matrices. Less