Tribological response and surface evolution of copper metal matrix composites under continuous sliding conditions at elevated temperatures

Temperature rise is a salient characteristic of friction brakes during continuous braking, and may cause undesirable changes to the performance of friction materials. New insights are put forward here regarding the evolution of frictional behavior and tribological mechanisms of copper metal matrix composites (Cu-MMCs) under continuous sliding conditions at 600 and 800 ℃. The friction coefficients exhibit clear trends across three distinct stages at two temperatures during continuous sliding. At 600 ℃, the wear rate of Cu-MMC increases noticeably with an increase in the sliding time, the friction coefficient initially increases, then experiences a slight decrease, and eventually stabilizes. The wear mechanisms of Cu-MMC evolve from slight adhesive wear, abrasive wear and oxidative wear to mild adhesive wear, oxidative wear and severe abrasive wear. At 800 ℃, as sliding time increases, the friction coefficient decreases sharply at the beginning of sliding, and subsequently stabilizes. The wear rate of Cu-MMC decreases notably with increasing sliding time. The wear mechanisms of Cu-MMC transition from severe abrasive wear, adhesive wear, and oxidative wear to delamination, oxidative wear and mild abrasive wear.