The Characterization of Running-In Coatings on the Surface of Tin Bronze by Electro-Spark Deposition

Antifriction materials, such as silver, copper, Babbitt B83, and graphene oxide (GO), were used to prepare running-in coatings on the surface of bronze QSn10-1 by electro-spark deposition (ESD). The analyses of mass transfer, roughness, thickness, morphology, composition, nanoindentation, and tribological properties of the coatings were investigated. The results showed that the running-in coatings were dense with refined grains that were uniformly distributed and in a metallurgical bond state with the tin bronze substrate. At optimum process parameters, the mass transfer was 244.2 mg, the surface roughness was 15.9 mu m, and the thickness of the layers was 160 mu m. The diffraction peaks clearly indicated the phases corresponding to alpha-Sn, SbSn, Cu6Sn5, and Cu, and a phase of Ag3Sn appeared. The modulus and the hardness of the running-in coatings were 24.9% and 14.2% of the substrate, and the deformation ratio of the coatings was 10.2% higher than that of the substrate. The friction coefficient of the running-in coatings was about 0.210 after the running-in stage, which was 64.8% of that of the substrate (0.324). The main wear mechanism of the running-in coatings under optimal process parameters is plastic deformation, scratching, and slight polishing. The running-in coating deformation under the action of high specific loads provides the automatic adjustment of parts and compensation for manufacturing errors.