Self-Organized High-Hardness Thermal Spray Coatings

We present a new dealloying-based technique to form fully-dense and high-hardness metal composite coatings. By depositing then heat treating a TiCr alloy coating on a Ni-base superalloy, a eutectic reaction occurs at the coating/substrate interface, which drives spontaneous pattern formation in both alloys analogous to liquid metal dealloying. The coating exhibits a significantly higher hardness (15 GPa) than both the starting alloy (3.7 GPa) and precursor coating (6 GPa), measured by micro- and nanoindentation, while maintaining the ability to plastically deform during micro-indentation experiments without apparent cracking or spallation. The flexibility and scalability of the dealloying process used here demonstrates a promising route towards protective coatings for structural alloys.