Investigation of AerMet100 segregation behavior during casting and homogenization by quantitative electron microscopy and thermodynamic/kinetic modeling

Abstract

Dendritic segregation of alloying elements during solidification results in non-uniform chemical and mechanical properties of steels. Homogenization can reduce the composition imbalances and restore uniformnity of mechanical properties. AerMet100 is a high alloy steel produced in wrought forms by Carpenter Technology, Inc. for applications requiring a combination of high strength, high fracture toughness, and resistance to stress corrosion cracking. The nominal composition is (wt%) 13.4% Co, 11.1% Ni, 3.1% Cr, 1.2% Mo, 0.23% C, and the balance Fe. Recent studies of cast and homogenized AerMet100 have demonstrated the mechanical properties approaching the high levels of wrought AerMet100. Optimization of a homogenization treatment for elimination of the microsegregation developed during solidification was completed using thermodynamic/kinetic modeling and quantitative energy dispersive spectrometry (EDS) in scanning electron microscopy.The as-cast alloy has the classic fern-like dendritic structure shown in Figure 1. The primary dendrite arm spacing was 150-400 μm and the secondary arm spacing was 70-110μm.