Industrial-Scale Evaluation of Zinc–Iron and Tin–Iron Alloy Powders for High-Performance Copper-Free Brake Applications

Copper (Cu) has long been used in brake friction materials due to its high thermal conductivity and stable friction behavior; however, environmental concerns have driven the development of Cu-free alternatives. In this study, iron–zinc (Zn-Fe) and iron-tin (Sn-Fe) alloy powders were investigated as potential substitutes for Cu in brake pad formulations. Zn-Fe and Sn-Fe–powders were produced via mechanical alloying, and their performance was compared with a Cu-containing formulation. The developed brake pads were characterized in terms of porosity, hardness, thermal conductivity, and tribological behavior using a Chase test. The results showed that the Zn-Fe-containing sample (ZF10) exhibited the highest hardness (104.7 HRM) and superior wear resistance, with the lowest weight loss (2.30%), compared to the Cu-containing sample (CO10, 3.15%) and the Sn–Fe sample (SF10, 3.86%). In addition, ZF10 demonstrated the highest average coefficient of friction (0.515), indicating improved friction performance. Although the Cu-containing sample showed the highest thermal conductivity (5.65 W/mK), the Zn-Fe and Sn-Fe systems provided stable friction behavior and good fade resistance at elevated temperatures. These findings indicate that Zn-Fe intermetallic phases significantly enhance wear resistance and friction stability, while Sn-Fe systems offer acceptable performance within Cu-free formulations. Overall, Zn-Fe alloy powders, in particular, emerge as promising and environmentally friendly alternatives to Cu for next-generation copper-free brake pad applications.