Investigation of creep cavities in a novel 12Cr0.36Ta steel employing three-dimensional electron backscatter diffraction technique

Abstract

Cavities are examined in a 12Cr0.36Ta steel specimen crept at 650°C/130MPa employing three-dimensional (3D) electron backscatter diffraction (EBSD) technique. Observation revealed that cavities are formed at the junctions where high angle grain boundaries (HAGBs) and low angle grain boundaries (LAGBs) coincide. Activation energies required for cavity formation at the junctions of four and three grains/subgrains are lower compared to nucleation in the bulk. This makes four and three grain/subgrain junctions prone to creep cavitation. Cavities have grown towards the highly misoriented grains. 3D reconstruction revealed that cavities are interconnected in reality that cannot be visualized from the two-dimensional (2D) investigations. At moderate stress level, as in present situation cavities have disc type morphology.