Processing of MAX phases: From synthesis to applications

MAX phases are a large family of materials with more than 150 different compositions that have been extensively investigated during the last 25 years. They present a layered structure and a unique combination of properties, bridging the gap between metallic and ceramic properties. However, despite their excellent response of some compositions at high temperature—excellent oxidation resistance up to 1400°C under corrosive environment, good damage and radiation tolerance, thermal shock resistance, and self‐crack healing—their transfer to applications has been limited by three main factors: i) complexity of this large family of materials, ii) unavailability of highly pure commercial powders, and iii) extensive time to license products in strategic fields such as nuclear or aviation. In this article, the main properties and synthesis routes are reviewed, including solid state reaction methods, physical vapor deposition (PVD) techniques and molten salt processes. Emphasis is given to processing routes for developing different structures such as dense bulk samples, ceramic matrix composites, foams with different porosity, coatings by PVD and thermal spray technologies, and near net shaping by slip casting, injection molding, and additive manufacturing. Well‐known and novel potential applications are described such as structural materials for high temperature applications, protective coatings and bond‐coats for gas turbines, accident tolerant fuel cladding in nuclear power plants, solar receiver in concentrated solar power systems, electrical contacts, catalyst, and joining material. Finally, high impact investigations and future challenges are listed in order to facilitate the transfer of MAX phases to the market.