Intermediate temperature brittleness of Ni based superalloy Nimonic263

Ni based superalloy Nimonic263 offers excellent resistance to corrosion and high temperatures, and as such can be used under an A-USC environment, which has extremely high temperatures and high pressure. To investigate the intermediate temperature brittleness that is the temperature dependence of this alloy, the tensile test was carried out at a constant cross head speed of 1 mm/min in the temperature range of room temperature to 900 degrees C. As the temperature increased during the test, the constant yield strength decreased sharply at 800 degrees C while the ductility began to decrease from 500 degrees C and then recovered after showing a minimum value at 800 degrees C. The results of the OM, SEM and TEM observations indicate that the deformation mechanism changed from gamma' shearing to bypass as the temperature increased, and the minimum ductility resulted from decohesion of the glide plane.