Fatigue crack initiation and propagation in several nickel-base superalloys at 650°C

摘要: Abstract The modes of crack initiation and propagation several nickel-base superalloys have been examined after fatigue creep-fatigue testing at 650°C. In fatigue, was transgranular frequently associated with porosity or inclusions in the higher strength alloys. These defects were usually located surface, except for tests low strain ranges where larger, internal often initiated failure. Although transgranular, those alloys grain sizes less than 15 μm, growth quickly became intergranular. This transition environmentally assisted did not occur subsurface cracks until broke through to atmosphere. cycle, which included a 900 s tensile dwell, wer e both intergranular all