Microstructure Evolution and Corrosion Performance of Additively Manufactured GH4099 Superalloy Produced by Selective Laser Melting

In this work, the microstructure evolution and corrosion performance of additively manufactured GH4099 superalloy were investigated. The alloy samples were prepared by selective laser melting (SLM) technology with different laser power and scanning speed. The results showed that the GH4099 prepared by SLM had a fine grain structure, and the average grain size of all samples is below 18 μm. The relative density of SLMed samples first rose and then fell as the volume density increased. Under the process conditions of P = 170 W and V = 800 mm/s, sample N2 possessed the highest relative density and the minimum pores. In addition, the electrochemical test results indicated that sample N2 exhibited the best corrosion resistance, and its corrosion potential (E_Corr) and corrosion current density (I_Corr) were − 0.287 V and 0.149 μA·cm⁻², respectively. The relative density and pores of the alloys were the main reason for the difference in corrosion properties. In particular, the irregular pores caused by lack of fusion were regarded as the initiation site of pitting and crack expansion, which has a greater effect on corrosion resistance than spherical pores. According to XPS results, the passivation film mainly consists of oxides and hydroxides of Ni, Cr, Co, and Al. The hydroxides of Ni, Cr, Co, and Al constituted the outer layer of the passivation film. After the dehydration reaction of hydroxides, their oxides formed the inner layer of the passivation film. In addition, the evolution of the passivation film including the formation and breakdown of the passivation film was also discussed.