Research on characteristics and deformation mechanism of Al2O3 inclusions with different forming processes in powder metallurgy superalloy

Abstract

In this study, the defects of powder metallurgy superalloys, specifically, the characteristics of aluminium oxide (Al2O3) inclusions in the primal powder superalloy FGH96, were investigated. In addition, the deformation mechanism of Al2O3 inclusions from different forming processes, such as hot isostatic pressing (HIP), hot isostatic pressing and hot isothermal forging (HIP+HIF), hot isostatic pressing and hot extrusion (HIP+HEX) and hot isostatic pressing, hot extrusion and hot isothermal forging (HIP+HEX+HIF), was studied. The results showed that the major types of inclusions in primal powder were Al2O3 and silicon dioxide (SiO2). The Al2O3 inclusion showed purely mechanical bonding with the matrix, and it always ran through several grains. The HEX process played the most important role in crushing Al2O3 inclusion, which was elongated and broken into hundreds of tiny ones along the extrusion direction; there was no effect from the HIP process on the inclusion crushing, and the HIF process had a certain amount of effect in between the HIP and HEX processes.