Parameters in selective laser melting for processing metallic powders

Abstract

The paper presents results of studies on Selective Laser Melting. SLM is an additive manufacturing technology which may be used to process almost all metallic materials in the form of powder. Types of energy emission sources, mainly fiber lasers and/or Nd:YAG laser with similar characteristics and the wavelength of 1,06 -1,08 microns, are provided primarily for processing metallic powder materials with high absorption of laser radiation. The paper presents results of selected variable parameters (laser power, scanning time, scanning strategy) and fixed parameters such as the protective atmosphere (argon, nitrogen, helium), temperature, type and shape of the powder material. The thematic scope is very broad, so the work was focused on optimizing the process of selective laser micrometallurgy for producing fully dense parts. The density is closely linked with other two conditions: discontinuity of the microstructure (microcracks) and stability (repeatability) of the process. Materials used for the research were stainless steel 316L (AISI), tool steel H13 (AISI), and titanium alloy Ti6Al7Nb (ISO 5832-11). Studies were performed with a scanning electron microscope, a light microscopes, a confocal microscope and a µCT scanner.

Hot Corrosion of Ti–Re Alloys Fabricated by Selective Laser Melting

“…Hot corrosion of Ti-Re alloys in the mixture of Na 2 SO 4 and NaCl salts at 600°C leads to the formation of non-protective TiO 2 (rutile) scale which spalls off easily [23,24,27]. As the exposure time is extended, the oxide scale gets thicker and starts to spalls off after reaching a certain thickness as shown for SLM-Ti after 100 h. However, the presence of corrosion products in Ti-Re alloys after the same exposure time suggests the stronger adhesion of the oxide scale to the substrates in comparison with pure titanium.…”

“…The weight loss per unit area of the SLM-Ti-Re alloys as a function of the exposure time in the mixture of Na 2 SO 4 and NaCl salts at 600°C is shown in Fig. 3.…”

“…X-ray diffraction patterns for Ti-Re samples annealed in the mixture of Na 2 SO 4 and NaCl salts at 600°C for different times are shown in Fig. 4.…”

“…Liquid titanium readily dissolves rhenium; however, the presence of some larger Re particles in the powders mixture Fig. 7 a, b Surface morphology of Ti-2Re after hot corrosion test in the mixture of Na 2 SO 4 and NaCl salts at 600°C for 100 h; c mass contrast image of area corresponding to (a) with the results of EDS analysis in marked points increases the risk of incomplete rhenium dissolution due to the insufficient energy density of scanning laser beam [14]. Therefore, to determine the degree of rhenium dissolution by the SLM process, computed tomography measurements were Table 1.…”

“…During the SLM process, thin metallic powder layers (50-100 lm) are spread out on a building platform and subsequently fully melted and consolidated by a scanning laser beam. Building objects layer by layer allows 3D metal parts to be obtained [1][2][3][4]. SLM offers several advantages over the conventional manufacturing techniques such as reduction in processing steps, high material utilization and a near-net shape production of the geometrically complex shapes with a minimal machining [5,6].…”