The Physics and Mechanics of Creep Cavity Nucleation and Sintering in Energy Materials

The research project will study the physics and mechanics of creep cavity nucleation and the reverse process of healing by sintering in polycrystalline materials for energy applications using both modelling and experimental approaches. The experimental work will focus on a model single phase material (commercially pure Nickel), a simple particle strengthened material (Nickel with addition of Carbon), a commercial austenitic stainless steel (Type 316H), a superalloy (IN718) and a martensitic steel P91/92. An array of state-of-the-art experimental techniques will be applied to inform the development of new physics-based cavity nucleation and sintering models for precipitation hardening materials. Once implemented in mechanical analyses, and validated, such models will form the basis for development of improved life estimation procedures for high thermal efficiency power plant components.

The life of modern (and legacy) power generating plant is limited by the high temperature performance of the construction materials. But our continuing lack of understanding of the underlying processes controlling nucleation of creep cavities (i.e. damage) means that empirical models fitted to macroscopic data are currently employed by industry to assess creep failure and define safe operating life. The reverse process of cavity healing by sintering has received even less attention than nucleation, but is equally important in developing mechanistic understanding. The fundamental insights, knowledge and models arising from the proposed research programme will allow more physically based design and assessment procedures to be developed for high temperature power generating plant. This will help to underwrite life extensions of legacy power generating plant that are limited by the high temperature performance of the construction materials, as well as supporting future designs of power generating plant that must exceed a 60 year life specification. Moreover a deeper understanding of cavities sintering opens up new opportunities for designing components and thermomechanical histories that promote self-healing in-service and extending a component's life. The research project will have far reaching national and international academic impact because of the fundamental nature of the proposed modelling and experimental studies, widespread industrial impact owing to the potential for improving design methods and lifetime assessment procedures, societal benefits through improved assurance of fail-safe operation of power plant, substantial economic benefits arising from life extension of legacy power plant (and longer design life for new power plant), as well as the training of 3 post-doctoral researchers, 4 PhD students and the strengthening of leading UK research groups working in the high temperature materials field.