Deformation mechanism and quantitative characterization of Al2O3 inclusions in powder metallurgy superalloys

By means of implanting inclusions artificially, the evolution law of three-dimensional morphology and size of Al2O3 inclusions in FGH96 powder metallurgy (PM) superalloy during hot iso-static pressing (HIP), hot extrusion (HEX) and hot isothermal forging (HIF) process was investigated by SEM and quasi in situ Micronano-CT. The size change of inclusions during different stages was studied quantitatively, the three-dimensional (3D) morphology of the inclusions was characterized, and the deformation mechanism was proposed. The results showed that the inclusions in powder stage were long stripe or plate-like shape. During HIP, Al2O3 inclusions were mechanically bonded to the alloy matrix, and its chemical composition, morphology and size remained unchanged. During HEX, Al2O3 inclusions were broken and elongated into chain shape due to shear stress. The quantitative relationship between inclusion size after extrusion and extrusion ratio as well as original inclusion size was established. During HIF, the relationship between 3D morphology, size, orientation and deformation of a single inclusion during forging compression was quantitatively characterized by quasi in-situ micronano-CT for the first time. The above evolution law provides theoretical basis and technical support for improving the purity level of powder turbine disk.