Yoshifumi Amamoto

Effect of varying load on wear resistance of carbon steel under unlubricated conditions

Abstract Pin-on-disk type wear tests of mild steel in contact with itself were conducted under unlubricated conditions in moist air to investigate the effect of changes in load on the transition behavior between severe and mild wear. Machines in operation are usually subjected to varying loads. In this study, two contact load levels were used as a simple varying load condition. The load was changed in a step-wise manner between the low and high levels either once or twice during certain tests. Severe wear appears at the high load levels and mild wear at the low load levels in wear tests under constant loading. After oxidized, work-hardened wear surfaces have been formed under mild wear at the low load during the first stage, the wear mode changes to “quasi-mild wear” having a low rate at the high load in the final stage. The load range, where the low wear rate can be maintained under quasi-mild wear, extends to the higher load level after the change(s) in load. Once the quasi-mild wear surface has been generated, the wear mode can be maintained even at the high load for a very long sliding distance.

Effects of Contact Load on Fretting Wear of Al-Si Alloy Impregnated Graphite Composite

An Al-Si alloy impregnated graphite composite (ALGR-MMC) containing a large amount of graphite (56 vol%) has been newly developed to improve the friction and wear characteristics of machine components such as clutches under dry sliding and journal bearings under lubricated sliding. The ALGR-MMC has the same self-lubricating performance as graphite in moist environments. It has good properties of thermal expansion, heat resistance and wear resistance. The objective of this study is to investigate the friction and wear of the ALGR-MMC under fretting conditions. Ball-against-disk type fretting wear tests for the ALGR-MMC (flat) in contact with bearing steel (ball) were conducted at various contact loads in moist air under unlubricated conditions. The friction coefficient was monitored during the tests. The area and depth of wear scars were measured after the tests or in the interrupted tests. From the friction and wear data, the effects of contact load on the fretting wear characteristics of the ALGR-MMC were evaluated with SEM observations of wear scars and EPMA analyses of wear surfaces.© 2005 ASME