AbstractThe structure and composition of an innovative Ti-Cu intermetallic coating has been investigated by means of metallographic examination, X-ray diffraction, glow discharge optical spectroscopy, and microhardness measurements. For this purpose, Ti-6Al-4V substrates were coated with a uniform layer of copper by an electroplating technique, then a diffusion anneal was conducted in an argon controlled atmosphere. Microstructural examination revealed that the compound coating microstructure consisted of four layers: the outer two layers are composed of various intermetallic compounds, including TiCu3+ Ti3Al and TiCu; the third layer is the transformation product of theβphase electroplatformed at the diffusion temperature, which containsα- Ti and Ti2Cu; and the fourth layer was identified as the product of this transformation precipitated mainly at proeutectoid (α- Ti boundaries. These microstructural features reveal the two essential characteristics of the coatings, namely the continuous layers of intermetallic compound and a substrate hardened by inward diffusion of a substitutional alloying element.