General (vertical) and objective (horizontal) R & D on heat-resistant materials
- Taking the case of superalloys for gas turbines -
Ohtani Ryuichi
Abstract:Nickel base and cobalt base superalloys for landed and aerospace gas turbines are situated between in ready made, existing materials and in order made, advanced materials. Although the development of elemental materials, evaluation of structural materials, design of parts and maintenance of structures have been performed rather independently in each general (or vertical) research and development (R & D) units for the existing materials, they have to be investigated in close connection with each other as an objective (or horizontal) R & D for the advanced materials. In this paper, some required subjects for the objective R & D are pointed out by taking the case of superalloys for gas turbines: necessity of out of phase thermal fatigue resistance, crack propagation analysis and coating materials design in the development of materials, importance of inelastic analysis for crack tolerance design, fatigue life evaluation under compressive strain hold cycling and coating effect on crack initiation in the design of structural materials, and difference between pathological and clinical approaches and applicability of inverse analysis for remaining life prediction in the diagnostics of structures in service. Key Words:superalloy, gas turbine, material design, materials evaluation, diagnostics