Creep, fatigue and creep-fatigue behaviour of martensitic/bainitic steels and nickel-based alloys and their welded joints at the temperature range 500°C–750°C

Abstract

ABSTRACT The aim of the paper is to investigate experimentally the fatigue and creep-fatigue material behaviour of improved materials and welded joints for the application in flexible future power plants. These materials promise a reduction in manufacturing costs as well as an increase in flexibility by providing enhanced creep strength thorugh a wall thickness reduction. At the temperature range between 500°C −550°C, the investigation focusses on the creep and low-cycle fatigue behaviour of dissimilar welded joints from conventional materials (bainitic and martensitic materials T24 and T92) to nickel-based alloys (A617B and HR6W) fabricated as tubes. At the temperature range between 700°C and 750°C, it focusses on the creep, low-cycle fatigue and creep-fatigue behaviour of similar and dissimilar welded joints from nickel-based alloys (A740H, A617B and A263) fabricated as tubes and as pipes. Metallographic investigations after testing provide support for understanding the influence of temperature, strain amplitude and dwell time on the microstructure change and the fatigue strength.