Investigation on Microstructural Properties of 3D Printed and Thermally Sprayed Alumina

The important microstructural characteristics of 3D printed alumina (Al₂O₃) using laser stereolithography (SLA) were compared to the ones produced via Air Plasma Spraying (APS) and Detonation Gun Spraying (DGS) in this study. All samples were subjected to Scanning Electron Microscopy (SEM). The microstructure of AM produced was mostly consisted of alumina and voids while both types of coating samples contained extra features such as splats, pores, cracks, and boundaries The DGS deposited alumina was characterized by higher density as compared to the APS coating. The density value of AM processed sample was in between those of the two coating samples. APS produced coating with higher porosity (10 ± 2%) followed by AM processed alumina (8.1 ± 0.8%) and DGS coating (3.0 ± 0.6%). EDS characterization indicated that both coating samples only contained aluminum and oxygen. However, some additional carbon was detected in AM processed sample, indicating the existence of binder (resin based) in the sample. The feedstock powder used for AM process and both thermal spraying methods was pure α-Al₂O₃. The XRD results showed no phase change in 3D printed samples but both deposited alumina coatings (APS and DGS) contained the mixture of α-Al₂O₃ and γ-Al₂O₃ phases.