Ni–bronze has relatively high strength among copper alloys, but heat–treated materials may be used instead of as–cast materials in order to further increase the strength. In addition, bronze–based members are often used as so–called sliding members, and improvement in friction characteristics is also required. The authors investigated the hardness of Cu–Ni–Sn alloys with and without sulfur as a function of aging condition, and found that the optimum condition of aging ranged at 350°C for temperature and from 20 to 30 h for time, with little effect of sulfur. However, it is necessary to study the impact resistance and friction characteristics as mechanical properties. In this study we evaluated the impact resistance and friction characteristics of the sulfide–dispersed Ni bronze specimens heat–treated optimally by means of Charpy impact test and pin–on–disk sliding test, respectively. As a result, impact value was higher than that of current Cu–Sn base alloys, in spite of a decrease by aging treatment. During the sliding test, sulfides caused formation of a thick film along the sliding direction on the specimen surface, resulting in achievement of stable friction phenomena.
