Optical diagnostics of selective laser melting and monitoring of single-track formation
The paper presents the results of the optical diagnostic of the single-track formation process during selective laser melting. The detection of the track defects (as balling effect, denudation, particle sweeping) is shown and the powder particles consolidation is visualized. It was defined, that the evaporation and thus formation of the specific gas-dynamic conditions is the significant physical effect in the melt pool zone. The particle in-flight velocity during coming in and out from the melt pool and the gas flow velocity were evaluated. The results allow evaluating the kinetics of the mass-transfer process during selective laser melting. It was clearly shown the material quality properties after the selective laser melting are strongly influenced by the formed thermal field in the laser-irradiated zone. This could be the basis for developing of the optical control and diagnostic system based on the melt pool and adjacent zones temperature.