Zechen Du

This paper investigates the intergranular failure and degradation process of HR3C steel during creep. Substantial microscopic information for the morphological and compositional characteristics of intergranular precipitates were revealed here. The results showed that the intergranular M₂₃C₆ carbides precipitated progressively, resulting in a formation of Cr‐depleted region, and coexist with the NbCrN phase at the grain boundary. Besides, the dislocation configuration and density of HR3C steel also changed remarkably after creep, which manifests that the increase of lattice debonding extent and irregular atoms array. The intergranular damage of the M₂₃C₆ matrix interface was revealed by the HRTEM observation, and the main damage features were the volumetric defect generation as well as the large‐area distortion of atom lattice around the M₂₃C₆, which would contribute to the intergranular crack forming at the end of creep stage.

Plastic damage assessment in 316 austenitic steel was performed in this research by using the misorientation parameters derived from an in situ EBSD technique. With the increase in plastic strain, the misorientation parameters, such as the Grain Reference Orientation Deviation (GROD), Grain Orientation Spread (GOS), the Grain Orientation Spread over the grain Diameter (GOS/D), and Geometrically Necessary Dislocation (GND) density presented a growing trend. Nevertheless, the variation in GROD did not show a monotony trend, and the relative increase in the amplitude of GOS and GND density was less in the late plastic stage. Compared with the above parameters, the (GOS)/D exhibited a near-linear increase during the plastic tensile stage. As the specimen was stretched to a strain of 56.99%, the (GOS)/D increased 8.9 times compared with the original specimen. The results showed that the (GOS)/D parameter has the potential of becoming an indicator for the assessment of plastic damage in 316 steel.