Internal Pressure Creep Test and Life Evaluation for Full Size Reheat Elbow of Mod.9Cr-1Mo Steel

Abstract

In order to establish the life assessment method for the welded hot reheat elbow of modified 9Cr-1Mo steel, an internal pressure creep test is conducted with a full size elbow component. The results are following, (1) : The elbow component finally leaked at weld metal. The rupture time was 1606 hours. The creep damage seemed to be initiated near the inside surface of the elbow and to grow towards the outside surface along to the fine-grained HAZ of the seam weld. In outside neighborhood, the crack that had initiated along the fine-grained HAZ changed the direction of initiation into the weld metal. (2) : The results obtained by the Time of Flight Diffraction (TOFD) inspection for detecting cracks under the surface at the seam weld on the intrados of the elbow show the presence of a crack near the inner surface of the elbow at the end of life. (3) : The fracture life of the full size elbow internal creep test based on the stress level at the mean diameter formula was slightly shorter than the uniaxial creep test results.