Sintered Cu-based frictional materials were developed by using powder metallurgy (PM) method. The materials are aimed for application in a passenger car as a dry friction clutch. Effects of sintering temperature and composition on mechanical and tribological properties were determined. It was found that improper frictional material formulations caused inferior properties, particularly when the sintering temperatures were increased. Admixing of high Sn content (8 wt. %) resulted in decreases of sintered density and hardness with increasing sintering temperature. High Sn contents caused swelling of the sintered materials. Tribological properties (friction coefficient and wear rate) of the sintered specimens of the investigated materials were insensitive to sintering temperatures in the range of 800-950 °C but they were strongly influenced by chemical compositions. Addition of 3 wt. % graphite lowered the friction coefficient, which subsequently lowered the wear rate of the sintered material. To increase friction coefficient, one of the crucial properties of the dry friction clutch, of the sintered Cu-based frictional materials, two approaches were employed. In the first approach, substitution of graphite by SiO2 powders could improve the material friction coefficient. In the second approach, decreases of graphite content from 3 to 1 wt. % and of Sn content from 8 to 2 wt. % were conducted. The latter approach not only improved friction coefficient but also improved sintered density and hardness of the Cu-based frictional materials.
Sintered frictional materials (SFMs) were fabricated by using powder metallurgical process. Powder formulations were experimented to investigate effects of Sn, C and ZrO2 additions on mechanical and tribological properties of the sintered composites made for dry frictional materials applications. The developed SFMs consisted of non-lead friction material. Natural sand (SiO2) and ZrO2 were employed instead of lead oxide to provide frictional components. Interrelationships between chemical composition, sintering temperature, friction coefficient, wear behavior and mechanical property of the SFMs have been studied. It was found that sintering temperature affected hardness property of the SFMs. The hardness was also affected by SFM compositions. Friction coefficient increased with increasing ZrO2 content. Addition of natural sand resulted in decrease of the hardness of the SFMs. Graphite also affected hardness and friction coefficient of SFMs containing no sand. Employing prealloyed Cu-Sn powders provided SFMs with better mechanical properties compared to the SFMs made of admixed Cu and Sn powders.
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