A.V. Gusarov

New Approach of True Temperature Restoration in Optical Diagnostics Using IR-Camera

The laser treatment processes are specified due to the laser-matter interaction instabilities. Modern additive manufacturing technologies such as selective laser melting provide layer-by-layer part growth with continuous operation for hours and days but without adequate controlling systems at present. In this paper, a method for determining a temperature in the laser action zone during the process based on a study of microscopic structure, phase and element analyses of the processed material is proposed. A fixed point corresponding to melting temperature was acquired, and the corresponding emissivity coefficient was calculated with the assumption of its wavelength and temperature independence. The experimental data were corroborated with good agreement with mathematical calculations. The obtained results reveal an impact of scanning speed and of laser emission power on temperature in molten zone, which presents interest for optimization of laser-processing technologies and more specifically selective laser melting process parameters.

Modeling the Effect of Beam Shaping at Selective Laser Melting

The influence of the laser-beam radial distribution of the energy flux density is theoretically studied for the Gaussian distribution (mode TEM00), and doughnut distribution of TEM01* mode for the values of the Peclet number from 0 to 3. The model of linear thermal conduction in the target indicates that profile TEM00 is the best for thermo-activated treatment processes that can be accomplished in a wide temperature range and profile TEM01* can be advantageous for a narrow range of the permissible processing temperature. If the phase transitions of melting/solidification and evaporation are included into the model, the estimate of the width of the laser-treated band is reduced but the tendencies predicted by the linear model are not changed.

Synthesis of Nanostructured WC-Co Hardmetal by Selective Laser Melting

Selective laser melting is a layer-by-layer technique to form a solid part from powder. The thermal cycle of this process can be as short as one millisecond and less. This is why it is favorable to obtain nanostructured materials with advanced properties. Metal matrix composite WC-Co is studied. Micron-sized Co powder was mixed with WC nanopowder in a planetary ball mill to prepare uniform composite powder. Single remelted beads and monolayers were obtained from the composite powder on the substrates of sintered WC-Co. No cracks and good adhesion to the substrate are observed. The high cooling rate up to 106 K/s explains the fine microstructures. Increasing the scanning velocity is favourable because of refining the microstructure and decreasing the balling-effect. The attained values of surface roughness are as low as 1-2 μm.

Selective Laser Melting of 3D Structures Produced from Heat-Resistant Cobalt Alloys

The technological possibilities of 3D object manufacturing with complex geometry from heat-resistant cobalt alloy by method of selective laser melting is considered in the work. The boundary conditions of the SLM and the way of its overcoming are demonstrated.