Abstract Scope |
Fall-in superalloy material from crown, shelf, or consumable electrode during vacuum arc remelting may lead to the formation of Dirty White Spots (DWS), which have a deleterious effect on fatigue performance and have been known to cause sudden, uncontained jet engine failures. This work seeks to explore the contribution of process transients during VAR to the occurrence of DWS. This exploration uses a fully transient, 3D, process-scale VAR model coupled with Lagrangian particle tracking to determine the path and fate of fall-in material. This model is used then to parametrically study the effect of instabilities (e.g., sudden decreases or increases in process current, and asymmetric arcs). Additionally, safe ranges for the DWS precursor parameters of initial temperature, initial diameter, fall-in location, and drop height which yield complete precursor dissolution during these transient process conditions are estimated. Finally, this work suggests some optimal VAR process conditions which could be used to mitigate the occurrence of DWS without unduly raising the risk of other defects. |