Freckle Formation Propensity Criterion for New Superalloy Design

FrecklesFreckle are casting anomalies generally detrimental to the mechanical propertiesMechanical properties of superalloysSuperalloys. This work presents a new freckleFreckle formation propensity criterion calculated using only alloy composition to rank the freckleFreckle propensity of alloys when processed via the same melting route at common conditions This is achieved by combining literature established changes in density of solidifying liquid (Δρ/ρ) with an approximation for permeabilityPermeability within the mushy zoneMushy zone, using enthalpy of fusion, and solidificationSolidification range of the alloy. Also, a methodology to calculate Δρ/ρ using electron probe microanalysis (EPMA) on as-cast coupons of superalloysSuperalloys is outlined. Additional factors influencing the permeabilityPermeability within the mushy zoneMushy zone, such as the presence of primary carbides, can also be calculated based on alloy chemistry, and incorporated to refine the freckleFreckle formation propensity criterion.