Low load creep of nimonic 80A at about 750°C under constant and variable stress conditions

Abstract

Nimonic 80A specimens were tested in creep at 750°C under constant stress of 130 N mm −2 or variable stress between 110 and 150 N mm −2. An equation describing the stationary creep rate at constant stress has been derived. Electron microscopy observations have permitted the evolution of carbide and γ′ particles during the test to be followed and have helped to clarify the dislocation mechanisms of the high-temperature deformation. In particular, it can be demonstrated how a simple theory based on cumulative damage has limited meaning for a rigorous description of creep under variable stress conditions.