The effect of delta-ferrite in P92 steel on the formation of Laves phase and cavities for the reduction of low cycle fatigue and creep-fatigue life

Abstract

Tungsten containing P92 steel has been recognized as a material for steam power plant. Tungsten is known to be the main element to form the Laves phase during long-term exposure at 873 and 923K. It is found that delta-ferrite plays an important role in preferential formation site of Laves phase. The size and areal fraction of Laves phase in delta-ferrite are increased with increasing the aging time and temperature. Continuous low cycle fatigue and creep-fatigue tests with tensile hold time for 10minutes were conducted to investigate the effect of Laves phase on the reduction of fatigue life. It can be supposed that formation and growth of Laves phase in delta-ferrite during long time fatigue test worsen the material.