An overview of ceramic molds for investment casting of nickel superalloys

Abstract

Accelerating advancements in technological systems have demonstrated a need for alloys with drastically improved thermomechanical and chemical properties, called superalloys. Ceramic molds are typically used in near-net shape investment casting processes of superalloy components due to their chemical inertness and high-temperature capabilities. Ceramic molds, however, often suffer from shortcomings in vital properties including flexural strength, thermal shock resistance, permeability, dimensional stability, corrosion resistance, and leachability, which have restricted their ability to adequately process modern alloy castings. This study analyses these limitations and illustrates how to address them, particularly regarding ceramic mold and slurry design, processing of shells and cores, material selection, and testing and characterization. By utilizing advanced processing methods including additive manufacturing and gel-casting, more dimensionally accurate and preferentially built molds can be formed. Additionally, by varying the mold composition to achieve more chemically inert structures, reactions with the mold can be mitigated to reduce chemically induced defects.