Tribological and arc erosion behaviors of Cu-Nb and Cu-Cr in situ composites were investigated in this dissertation. Dry sliding tests were performed in a pin-on-disk wear tester with the composites rubbing against a rotating tool steel disk under ambient conditions with a pressure of 0.68 MPa, sliding speeds up to 2.5 m/s, and electrical current densities up to 2.89 MA/m[superscript]2. Electrical arc erosion tests were performed in a make-and-break test set-up and a high-energy stationary arc gap test facility;Sliding friction and wear behaviors of Cu-Nb composites with and without electrical loads were studied in terms of the effects of composition, filament orientation, true deformation strain, sliding speed and annealing temperature. The Cu-20 vol.%Nb composite had the best wear resistance among the compositions studied in both cases. Subsurface deformation was revealed by the presence of filaments and was one of the wear mechanisms for the composites. No debonding was observed in the composites during sliding. The presence of electrical current increased the temperature and promoted oxidation on wear surfaces;The contact behavior of Cu-Nb composites against tool steel was studied in terms of the contact resistance and temperature rise. Surface oxide film development, wear particle accumulation, and unsteady contact caused by sliding were found to be the major factors governing electrical contact resistance and, therefore, temperature rise. Arc erosion behavior of the composites was also investigated. It was concluded that, in low-energy make-and-break contacts, oxidation was the major mode of surface deterioration; and, in high-energy contact situation, melting was the major cause of surface damage. The Cu-refractory metal in situ composites had better arc erosion resistance in high-energy contacts than the commercially used Cu-W composite.