The purpose of this study is to examine the fretting behavior of the contacting surfaces between dissimilar metal. In this paper, an aluminum alloy (A2017) and a bearing steel (SUJ2) are employed as dissimilar metal. In fretting tests which are carried out in dry or oil-lubricated condition, relative slip amplitude and relative humidity in air are varied. From the results, it is found that the wear volume of A2017 is almost equal to that of SUJ2 in small amplitude in dry condition and that wear volume of A2017 are larger than that of SUJ2 as amplitude increase. In oil-lubricated condition, however, wear is caused only on A2017, and SUJ2 is hardly worn irrespective of relative slip amplitude. It is also found that wear particles influence the fretting behavior. The wear volume of A2017 in high relative humidity levels is smaller than that in low relative humidity levels. The wear volume of SUJ2 is independent of relative humidity.

Water lubrication was investigated with a double-network hydrogel (DN-gel) using a pin-on-disk tribometer. The friction coefficient obtained in water was 0.025. For IR measurement, a diamond prism of attenuated total reflectance (ATR) unit was in contact directly with DN-gel and the sliding experiments were carried out in water. IR spectra at the sliding interface were obtained by an evanescent wave with a Fourier transform infrared-attenuated total reflectance (FTIR-ATR) unit during lubrication tests. The concentration of water and gel at the interface was estimated from the IR absorbance of OH and CH stretching modes. It was found that the water content at the interface increased by sliding compared to a static condition and did not change with sliding speed but decreased with increasing load. In order to confirm the water source at the interface, the lubrication test was carried out in heavy water (D₂O) as a tracer. The water in the gel was not exchanged with D₂O. It can be concluded from the spectral data that the water at the sliding interface was mainly originated from bulk water (D₂O).

Experiments have been carried out to clarify the roles of matrix and dispersed NbC particles on the reinforcement of tool surface. It was at the end of the last century that outstanding performance in hot metal rolling was reported of the surface layer of tool reinforced with coarse NbC particles by Plasma-Transferred-Arc (PTA) welding but little has been investigated on the roles of matrix and optimum dispersion of NbC particles. In the present work specimens manufactured by PTA welding using NbC particles with different sizes and different fractions were subjected to hot sliding test against medium carbon steel in order to investigate the roles of matrix and the NbC particles held in the matrix. The result showed that the matrix is reinforced as soon as a small amount of NbC is injected into the welded layer and keeps the constant strength regardless of the increase in the fraction of NbC particles. With the increase in the fraction of NbC particles in the welded layer the performance of the surface increases linearly. In the previous use of coarse NbC powder was recommended but present result showed that the effect does not depend upon the size of NbC powder to be PTA-welded.