Formation of In Situ Al/TiAl₃ Coatings on Electron Beam Melted (EBM) Ti-6Al-4V Alloy by Cold Spray and Induction Heating

In this study, the formation of fast, hard, well-adhered and scratch-resistant in-situ composite coatings on electron beam melted (EBM) Ti-6Al-4V alloy were proposed by successive applications of cold spray (CS) and induction heat treatment techniques. The total treatment time to achieve such properties was around only 5 min. In this context, pure aluminum (Al) was first coated by CS technique on EBM Ti-6Al-4V alloy, and the coated samples were heat treated by induction heating method for different times (10 and 20 s). The coating layer that bonded well to the substrate material was obtained using the CS technique. After the induction heating, TiAl₃ intermetallics were formed in a sawtooth-like morphology as an interfacial layer at the substrate-coating interface. Similar to the interface, fiber and plate-like TiAl₃ compounds were found within the CS’ed coating layer. As the induction heating time increased to 20 s, the thickness of the interfacial layer and the fraction of intermetallics in the coating layer correspondingly increased. The highest hardness and scratch resistance were obtained in the 20 s induction-heated sample. Finally, this study demonstrates that the cold spray followed by induction heating is a rapid technique to obtain hard, well-adhered and scratch-resistant composite coatings in-situ on EBM Ti-6Al-4V alloy.