STUDIES ON FRICTION AND WEAR OF ALUMINUM ALLOY BASED COMPOSITES IN CORROSIVE ENVIRONMENTS

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Friction and wear tests under unidirectional and reciprocating sliding conditions were conducted in wet air, ion-exchanged water, saline solution, and machine oil to investigate the friction and wear characteristics of aluminum alloy (JIS AC8A) based alumina-short-fiber and hollow-silica-particle reinforced composites in corrosive environments.From the test results of unidirectional sliding wear of the composites in contact with a stainless steel, the rate of severe wear for the silica-particle reinforced composite in wet air is higher than the rate of other materials because the silica particles are fractured at high loads. The rate of mild wear is low at low loads because the particles bear a part of the load resulting in the improvement in the wear resistance. The transition load between severe and mild wear is about ten times higher in ion-exchanged water and saline solution than in wet air. The rate of mild wear is almost the same as that of AC8A,indicating no deleterious action o … More f the reinforcing material to be found.The wear resistance of the alumina-short-fiber reinforced composite in wet air is improved in the mild wear regime as compared with that of AC8A,however, is worse at high loads than other materials in all environments because the fragments of the reinforcing material exhibit abrasive action. The wear resistance is more decreased than AC8A in the aqueous solutions, indicating that the deleterious action of the reinforcing material is evident.The friction and wear test results of the composites against a bearing steel ball under reciprocating sliding in wet air reveal that the wear resistance of the composites are excellent at low loads. However, there is no great difference in wear resistance between the composites and AC8A with much wear of the steel ball at high loads.The wear resistance of the alumina-short-fiber reinforced composite is very good in machine oil as compared with other materials. A slight increase in the composite wear and the steel ball damage is seen even at high loads. The silica-particle reinforced composite manifests the wear resistance equivalent to that of the alumina-short-fiber composite at low loads. However, the wear rapidly increases at high loads due to the fracture of the silica particles, whose fragments accelerate the damage of the steel ball.The coefficients of friction mu of three materials are about 0.05 within a lower load range in machine oil and increase with load up to a constant value near 0.1 above 50N.On the other hand, the mu is about 0.5-0.9 in wet air and higher in the ascending order of AC8A,alumina-short-fiber, and silica-particle reinforced composites. The reason is that the plowing action due to the fragments of the reinforcing material embedded on contact surfaces exerts frictional resistance. Less