Novel method to fabricate Ti-Al intermetallic compound coatings on Ti-6Al-4V alloy by combined ultrasonic impact treatment and electrospark deposition

A Ti-Al intermetallic compound coating was fabricated on Ti-6Al-4V alloy by combined ultrasonic impact treatment and electrospark deposition. The principle of the combined process is described in detail based on studies of the chemical states, microstructure, phase compositions, microhardness, and surface residual stress of the coating. Many new Ti-Al intermetallic compounds distinct from the deposition materials are found to make up the coating, along with a small amount of Al₂O₃. The high energy of the electrospark facilitates the chemical reactions among elements. Further, the impact process produces a plastic deformation layer. The microhardness of the Ti-6Al-4V under the coating also increased because of the plastic deformation layer. Finally, the surface residual stress of samples treated by the combined process is compressive stress.