Product Engineers and Designers choose investment casting as a manufacturing method due to the tight tolerances that can be obtained, as well as, the exceptional mechanical properties achieved. Strict control of many variables is required to meet these demands. Important variables that play a primary role in the mechanical properties of an alloy are grain size, shape, orientation and resulting boundary.

The microstructure of a casting is controlled by the melt and pouring parameters along with the cooling rate and can be further influenced by subsequent heat treatment. However, grain nucleation is generally encouraged through the addition of a grain refining additive, which in the case of nickel and cobalt superalloys is cobalt aluminate. Over the years, cobalt aluminate manufacturing and application has been refined and improved to its current position as a highly technical and well understood component of investment casting. It is the purpose of this paper to provide a widerunderstanding and update, regarding the relationship betweenthe chemistry and structure of cobalt aluminate and its capability to provide the Investment Caster with a useful tool to assist in optimizing mechanical properties.