Thermal simulations for the prediction of porosity in investment castings for stellite grade superalloys

A computer model was constructed and run to predict the thermal history of a Stellite alloy investment casting prone to the formation of microporosity. The thermal history of the casting was utilized to calculate the thermal gradient at a specified temperature, the rate of cooling during solidification, and the solidification velocity. These parameters were combined in a manner consistent with the formulation of two different criteria (Niyama and L.C.C. criteria) used to predict porosity. The Niyama and L.C.C. criteria successfully predicted the distribution of porosity found in the actual investment casting. Several new casting configurations were designed and modeled on computer until a configuration was constructed that predicted very little or zero porosity in the problematic areas. A new casting configuration, similar to the one designed in this study, was designed and cast by the industrial sponsor. The computer simulation of the casting configuration by the industrial sponsor predicted a small pocket of microporosity. Upon examination, some microporosity, consistent with the predictions by the model, was discovered. The finite element modeling software (ProCAST™) and the Niyama and the L.C.C. criteria served as excellent tools for predicting porosity in Stellite alloy castings.Applied Science, Faculty ofMaterials Engineering, Department ofGraduat