I. Zhirnov

Determination of True Temperature in Selective Laser Melting of Metal Powder Using Infrared Camera

The objective of this study is to restore the true temperature in during the process of Selective Laser Melting (SLM) of metal powder (in the present case INOX 316L), that is the actual problem in laser assisted additive technologies. To meet this objective, at the first stage, the temperature was measured on the surface of metal substrate INOX 304L without a powder layer. Based on the results of studies the method of temperature measurementof the molten pool surface on metallic plates and during melting of metal powder layer, that were exposed to laser radiation, using an infrared camera (IR), in the present case FLIR Phoenix RDAS TM, was proposed. To restore the true temperature based on the brightness temperature values measured by IR camera, the results of temperature measurements were compared with the width of the molten track on the surface of the plate in the absence of powder. In case of SLM, the results of IR camera measurements were compared with the width of a welded track (bead). The true temperature profiles and temperature gradients values were determined along the axis of the laser beam for melting of plates without powder. In the case of powder melting, the developed method allows to determine the influence of several key SLM parameters on the molten pool shape.

Optical Monitoring and Diagnostics of SLM Processing for Single Track Formation from Co-Cr Alloy

The article presents a study of selective laser melting process (SLM) namely a study of stable track formation by the example of Co-Cr alloy. The characterization of the main process factors, which have an influence on the parts’ functionality, is developed. The experimental work for the research of two main factors as laser beam power and scanning speed showed the technological gaps for the formation of the stable tracks. The characterization of the non-stable single tracks’ defects is established. The new data about the main physical effects in the treatment zone is received by optical diagnostics of the process.

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.

Track geometry in selective laser melting

The influence of the power-density distribution within the laser beam on the geometric uniformity of a single track in selective laser melting is investigated. Methods of modifying the mode composition of the laser beam are considered. Preliminary simulation of the power-density distribution in the beam is described. The distribution of heat absorption by powder in laser treatment is determined.