Quantification of Local Recrystallization and Its Relation to Imposed Mechanical Energy and Ductility Dip Cracking in High Chromium Nickel Alloy Groove Welds
Prior research aimed to contextualize DDC occurrences within the framework of imposed mechanical energy (IME). IME represents the absolute cumulative integral of experienced stress vs. strain and quantifies thermo-mechanical loading. The hypothesis posited that IME induced in specific temperature ranges for the tested filler metal 52 (FM-52) would correlate to DDC occurrences across the weld. These temperature ranges were low (LT, <800°C), DDC (CT, 800-1050°C), and recrystallization (RT, >1050°C). The working hypothesis stated that weld regions exhibiting high IMELT and IMECT combined with low IMERT were prone to DDC, whereas regions with relatively high IMERT were less susceptible to DDC. To validate this, an FEA model was simulated in SysweldTM based on a groove weld with FM-52 used as a filler for a FM-52 plate with a groove cut. Temperature, stress and strain data were extracted, and IME was calculated for each temperature range, generating IME contour plots for the weld. A crack location map was created based on analysis of the FM-52 weld. A correlation between IME and crack locations was observed, which was consistent with the hypothesis.
The objective of this work is to quantify carbide precipitation at grain boundaries, local recrystallization, and the effect of thermo-mechanical histories, correlating these to the local distribution of IME and DDC in the FM-52 weld. Computational precipitate modeling is done using PrismaTM, with validation being done through advanced metallurgical characterization. Metallurgical characterization techniques like electron backscattered diffraction (EBSD) are utilized for quantifying local recrystallization and kernel average misorientation (KAM). These parameters are then correlated with local IME distributions in DDC and DDC-free locations across the specified temperature ranges.