Additive Manufacturing: Segregation and Microstructural Study on the Oxidation Behavior of Additively Manufactured Inconel 625

Inconel 625 is a Ni-base superalloy has excellent resistance to oxidation in aggressive environments. In this work, high-temperature oxidation behavior and its mechanism of IN625 produced by Selective laser melting in longitude and transverse directions was studied and compared with that of the wrought alloy at 850 and 1000 °C in laboratory air. XRD, SEM, and EDX were used to characterize the oxidation behavior. The experimental results revealed that oxide scales of all superalloys were similar in nature and morphology with small differences due to additive manufacturing. Cross-sectional analysis showed the formation of a subsurface zone in which strengthening phases like (Nb,Mo)Ni are dissolved. Also, a thin layer of Nb-rich intermetallic precipitates formed in the immediate vicinity of the scale/alloy interface. Formation of oxide nodules inside the matrix of AM alloys can be related to prior oxidation test, where, the oxygen content of the starting powder materials for AM process may slightly influence microstructure as oxygen lead to the formation of oxide in the deposited material. Internal oxidation of alumina found in wrought alloy which was not observed for the AM alloys. In AM alloys, some oxide particles have been formed in the matrix.