Influence of Heat Treatment and Composition Variations on Microstructure, Hardness, and Wear Resistance of C 18000 Copper Alloy

The hardness and wear behavior properties of two C 18000 copper alloys with variations in Ni, Si, and Cr concentrations, both within the range of C18000 chemical analysis standard, were studied after the alloy samples had been prepared by melting and casting in sand molds and then heat-treated in solution using two-stage aging for different heating time periods. The results obtained from sample sets of the aforementioned two alloys, C 0 and C 1 , show that the alloy C 1 , with slightly higher Si and Ni and lower Cr concentrations than the alloy C 0 , produced significantly higher hardness values and wear resistance than the alloy C 0 . Optical and electron microscopy microstructure studies of representative samples revealed a copper matrix containing nickel and silicon in solution and precipitates of chromium and nickel silicides. By studying the wear surfaces and debris of the former samples with electron microscopy, different types of wear mechanisms including adhesive, abrasive, oxidation, and repeated-cycle deformation were found. The wear behavior was expressed as mass weight loss, which correspondingly shows a typical inverse relationship with the hardness values for both the C 0 and C 1 alloy groups. 1. Introduction A search of the literature for studies related to the wear behavior and hardness of C 18000 copper alloys after heat treatment was conducted; however, no significant publications were found in this field for these particular alloys. Nevertheless, there has been continuous work on copper alloys as well as other materials, such as Cu-Be alloys for engineering applications to reduce health risks and production costs, but these studies mostly focus on the functional requirements for each case. In addition, bronzes, such as aged cast C 95200 and C 95300 aluminum bronzes, are widely used in several tribological applications, improving wear behavior, friction coefficients, and favorable changes in microstructure [1]. Similarly, the tribological behavior of two Cu-Be alloys shows a transition in the wear mechanism from metallic wear to tribo-oxidative wear as the applied load is increased [2]. Cuss-toughened silicide alloys exhibit excellent wear resistance and a low friction coefficient at room temperature under dry sliding wear test conditions with hardened 0.45%？C carbon steel as the sliding-mating counterpart [3]. At a constant current density, the wear rate of Cu-Cr-Zr alloy decreases with aging temperature and reaches a minimum at 500°C; it then increases with further increasing aging temperature. The improvement in wear resistance is