INVESTIGATION ON FRICTION AND WEAR CHARACTERISTICS OF ADVANCED ALUMINUM ALLOY MATRIX COMPOSITE UNDER VARIOUS LUBRICATING CONDITIONS

研究了Al-Si合金浸渍石墨复合材料（ALGR-MMC）及其基体（石墨和Al-Si合金）与轴承钢在润滑滑动条件下的摩擦磨损特性。采用SAE 30发动机油，在干滑动、滴进润滑（0.005 ~ 1.00 cm ^3）和滑动前浸没润滑（90 cm ^3）条件下进行销盘式摩擦磨损试验。在整个试验过程中，连续监测摩擦和磨损的变化。对于Al-Si合金，油膜破裂发生在油滴小于0.03cm ^3处。在油膜破裂后，摩擦系数（f）和磨损率（w）急剧上升，导致配对表面损坏。石墨的f和w随润滑油量的增加而减小，但高于Al-Si合金和ALGR-MMC在浸没润滑下的f和w。随着润滑油用量的增加，ALGR-MMC的摩擦磨损性能逐渐降低，润滑油没有发生断裂 ...更多信息 膜和对反表面的损坏。f和w远低于基体，表明ALGR-MMC是一种优异的滑动材料，即使在润滑不足的滑动条件下也可以使用。在滴注润滑条件下，研究了空气相对湿度（RH）对ALGR-MMC磨损的影响。磨损曲线分为三种类型。在1型曲线中，在测试开始后紧接着稳态磨损出现销抬起。在第二类曲线中，经过第一类过程后，又出现了顶销现象，随后出现了油膜破裂。在3型曲线中，在试验的早期阶段，销抬起后不会发生磨损。在相对湿度为50 ~ 80%时，1型的出现频率较高。2型曲线仅在RH[小于或等于] 5%时出现，表明油膜破裂发生在非常低的湿度下。3型曲线出现在RH=10 - 50%的低湿度下。为了研究微动条件下接触载荷对ALGR-MMC摩擦磨损特性的影响，在湿空气中对复合材料（平板）与轴承钢（滚珠）进行了不同载荷下的平板-滚珠型微动磨损试验。从结果中发现两种类型的微动过程发生。在A型中，动摩擦系数（fk）在初始阶段很高，然后在稳态阶段fk急剧下降到一个恒定值。在B型中，f_k在整个试验中是恒定的。在75 ~ 100 N的高载荷范围内，相对滑移幅值不能保持在50μm，而在5 ~ 60 N的低载荷范围内，相对滑移幅值保持在50 μm。在整个测试过程中，B型的平均磨损率低于A型。两种类型的平均磨损率随着接触载荷从5 N增加到100 N而增加。两种类型的微动过程的发生是由于在每个测试中的铝硅合金和石墨的接触面积部分的差异。少

Friction and wear characteristics of Al-Si alloy impregnated graphite composite (ALGR-MMC) and its matrices (graphite and Al-Si alloy) in contact with bearing steel were investigated under lubricated sliding conditions. Pin-on-disk type friction and wear tests were conducted under dry sliding, drop-feed lubrication (0.005 to 1.00cm^3) before sliding and immersion lubrication (90cm^3) by using SAE 30 engine oil. Changes in friction and wear were monitored continuously throughout the tests. For the Al-Si alloy, a breakdown of oil film occurs below 0.03cm^3 of oil drop. After the oil film has broken down, the friction coefficient (f) and wear rate (w) rise drastically, causing damage to the counter surface. The f and w for the graphite decrease with increasing amount of oil but the values are higher than those of the Al-Si alloy and ALGR-MMC under immersion lubrication. A gradual decrease in friction and wear for ALGR-MMC with increasing amount of oil is found without the breakdown of oil … More film and the damage to the counter surface. The f and w are much lower than those for the matrices, indicating that ALGR-MMC is an excellent sliding material that can be used even under insufficiently lubricated sliding conditions. The f and w of ALGR-MMC go up with increasing X-ray intensity of Al and C of adhered films on the counter surface.The effects of relative humidity (RH) in air on the wear of ALGR-MMC were investigated under drop-feed lubrication. The wear curves were classified into three types. In Type 1 curves, the pin lifting appears just after the start of tests followed by steady state wear. In Type 2 curves, after the process of Type 1 the pin lifting appears again, followed by the breakdown of oil film. In Type 3 curves, wear dose not occur after the pin lifting in the early stage of the tests. The occurrence frequency of Type 1 is high at RH=50 to 80%. The Type 2 curves appear only at RH【less than or equal】5%, indicating that the oil film breakdown takes place at very low humidity. The Type 3 curves appear at low humidity of RH=10 to 50%. The steady-state wear rate is higher at high humidity and shows a maximum at RH=70% in the Type 1 curves.In order to investigate the effects of contact load on the friction and wear characteristics of an ALGR-MMC under fretting conditions, flat-against-ball type fretting wear tests for the composite (flat) in contact with bearing steel (ball) were conducted in moist air at various loads. From the results two types of fretting process were found to occur. In Type A, the coefficient of kinetic friction (f_k) was high in the initial stage followed by a drastic decrease in f_k to a constant value in the steady-state stage. In Type B, f_k was constant throughout the tests. The amplitude of relative slip could not be kept constant at a desired value of 50μm in the higher load range from 75 to 100N but kept in the lower load range from 5 to 60N. The mean wear rates throughout the tests in Type B were lower those that in Type A. The mean wear rate for both the types was increased with contact load from 5 to 100N. The occurrence of the two types of fretting process is due to a difference in the contact area portion of Al-Si alloy and graphite for each test. Less