This study compares the microstructure of Al 2 O 3 coatings produced by detonation gun spraying (DGS) and laser stereolithography (SLA). The SLA samples mostly consisted of alumina and voids, while the DGS-deposited alumina contained additional features such as splats, pores, cracks, and boundaries. DGS deposits were also denser with about 3% porosity compared to 8% porosity in the SLA samples. EDS analysis showed that both coatings contained only aluminum and oxygen, although additional carbon was detected in the SLA samples, indicating the presence of residual binder (resin based) material. XRD analysis revealed a mixture of α and γ-Al 2 O 3 phases in the DGS coatings, but no phase change in the SLA samples.

This study deals with two new material deposition processes in which raw materials are in the form of a thixotropic slurry. In one case, the slurry (Al 2 O 3 nanoparticles in an acrylic resin) is misted into an arc plasma jet and sprayed on a stainless steel substrate. By varying the volume content of nanoparticles and slurry supply rates, investigators were able to achieve uniform droplets, resulting in fine Al2O3 layers free of microcracks and pores. In the other process evaluated, pure aluminum particles were dispersed in a photosensitive resin, producing a slurry that was spread on stainless steel substrates then patterned with a UV laser. The patterned metal particles were heat treated, creating iron-aluminide intermetallic phases through reaction diffusions. The microstructure and composition of the patterned lines are analyzed by SEM and XRD and surface stress distributions associated with a Hilbert fractal pattern are simulated via finite element analysis.