Replenishing the limited Aluminium reservoir of MAX phase coatings in harsh environments

Projektbeschreibung

Verbesserte Stabilität von aluminiumhaltigen MAX-Phasen unter extremen Umweltbedingungen

MAX-Phasen sind Stoffe, die die positiven Eigenschaften von Metallen und Keramik in sich vereinen. Diese Klasse von ternären Schichtkeramiken hat vor allem deshalb so großes Interesse geweckt, weil die Materialien hohen Temperaturen standhalten können und selbstheilendes Verhalten zeigen. Dank dieser Eigenschaften sind sie für den Einsatz in extremen Umweltbedingungen geeignet. Aluminiumbasierte MAX-Phasen neigen aber zu lokaler Zersetzung, sobald das Aluminium mit Sauerstoff in Berührung kommt, und bilden eine dünne Oxidschicht aus. Das EU-finanzierte Projekt REALMAX will eine neue Materiallösung entwickeln, die der Instabilität der MAX-Phasen in extremen Bedingungen entgegenwirkt. Dazu sollen unter anderem Aluminium-Beschichtungen für die MAX-Phasen aus ihren eigenen Substraten gefunden werden und es wird untersucht, wie Legierungselemente auf die potenzielle träge Diffusion von Aluminium-Spezies wirken. Die Projektergebnisse werden tiefergehende Erkenntnisse über das Oxidationsverhalten von MAX-Phasen liefern und so einem aufstrebenden neuen Feld in der Werkstoff- und Ingenieurswissenschaft zuarbeiten.

Ziel

Phase stability is likely to be the single most important specification which determines the lifetime of materials operating in extreme environments. Whether a phase will react with the environment or decompose at high temperature is an essential limitation for the use of the material for any given applications. MAX phases are a family of layered ternary ceramics currently being developed for extreme environment applications because of their tolerance to heat, their ceramic-metallic hybrid properties and more importantly because of their self-healing behaviour. However, similarly to other self-healing materials, aluminium-based MAX phases tend to decompose locally as soon as Al reacts to form the protective oxide scale. Upon decomposition, the unique set of properties deteriorates rapidly.
The REALMAX project will tackle the outward diffusion of Al from MAX phase coatings in oxidising environments, by providing solutions for supplying Al to the coating from a MAX phase substrate which will act as Al-reservoir. Furthermore, the REALMAX project will engage in ground-breaking research to develop multifunctional coatings and validate the concept of “high-entropy” MAX phases. In fact, these multielement MAX phases constitute a new and exciting research line which is in the early stages of being developed.
The REALMAX project will be carried out by the experienced researcher (ER) who has gained experience on MAX phase coatings during her current postdoctoral position. The ER has aligned a team of experts in MAX phases, coatings and material processing who will collaborate to offer innovative solutions to increase phase stability in MAX phase systems while mentoring her to achieve her career plans. In fact, she will be well positioned to pursue her academic career in Europe, while simultaneously adding genuinely novel expertise approaches to the research environment and the group she will be joining. Therefore, the mutual benefit and impact of this proposal is extensive.