Towards Self-healing Creep Resistant Steels

We report the main findings of our work on the behaviour of binary Fe-Cu and Fe-Au model alloys designed to explore routes to create new creep resistant steels having an in-built ability to autonomously fill creep induced porosity at grain boundaries. The alloying elements were selected on the basis of their ability to be brought in supersaturation, their limited or even absent tendency to form immobile intermetallic compounds and their affinity to segregate to free surfaces. The model alloys were creep loaded to failure at various stress values at a fixed temperature of 550 0 C. As a result of creep loading, grain boundary cavities developed which were either fully or partially filled by the alloying element explored. The degree of pore filling was found to depend on the alloying element, the stress level and the orientation of the residing grain boundary with respect to the applied load. The clearest examples of full or partial pore filling were observed for the Fe-Au system. In addition to pore filling, extensive precipitate formation was observed in the Fe-Cu alloys.