Nanodispersing and Hardening in Technology of Selective Laser Melting of Metallic Powders

The structure of materials produced by selective laser melting from metal powders of different chemical composition is analyzed. For all samples obtained by melting, studies showed an increase in the strength characteristics over similar indices of monolithic samples of identical chemical composition. In the set experiments, the effects of the anisotropy of the properties, due to the samples growth direction, and hardening, which linearly increased with increasing of the laser energy, were recorded. A phenomenological model of phase nuclei formation is formulated by the mechanism of condensation of metal vapors formed above the melting zone. Completeness of the crystallization process determines the quality of the material obtained. It has been established that nanoparticles of vapor condensation above the melting zone and the peculiarity of the structure of materials obtained by selective laser melting, in the form of a combination of ultradispersed particles of a condensed state and needle-like crystallites (ultrafine-grained structure of crystallization) are factors of strength enhancement. The ultra-fine-grained structure of the needle-shaped species is formed by the mechanism of epitaxy at the stage of crystallization in microvolumes with a melt, depending on the temperature conditions. (paper)