This study proposes a novel wear protection strategy that focuses on the in-situ construction of an amorphous-nanocrystalline composite layer via friction-induced mechanochemical reactions. To realize this concept, a multicomponent (FeSiB)_xCu_y (at.%) alloy was selected as the precursor material. Subsequently, sliding wear tests were conducted under distinct normal loads (10 N and 30 N) to control the input of mechanical energy. Under the higher load, an amorphous-nanocrystalline composite structure was formed, with nanocrystalline Cu embedded in an Fe-Si-B-O amorphous matrix, indicating the incorporation of environmental O into the tribological layer during sliding. This composite layer significantly improved the wear resistance by the synergistic plastic deformation mechanisms during sliding contact.