I. Yadroitsev

Factor analysis of selective laser melting process parameters and geometrical characteristics of synthesized single tracks

Purpose – Properties of the parts manufactured by selective laser melting (SLM) depend strongly on the each single laser‐melted track and each single layer, as well as the strength of the connections between them. The purpose of this paper to establish links between the principal SLM parameters (laser power density, scanning speed, layer thickness), properties of the powder and geometrical characteristics of single tracks. This study will provide a theoretical and technical basis for production of parts from metal powders.Design/methodology/approach – This paper discusses the SLM parameters affecting on geometrical characteristics of the synthesized single tracks. Granulomorphometric characteristics of powders were studied in detail. A Greco‐Latin square design was used to control geometrical characteristics of the tracks. Analysis of variance (ANOVA) permitted to establish a statistically significant influence of the SLM process parameters on geometry of the single laser‐melted track.Findings – The behav...

Strategy of fabrication of complex shape parts based on the stability of single laser melted track

To up-grade selective laser melting (SLM) process for manufacturing real components, high mechanical properties of final product must be achieved. The properties of a part produced by SLM technology depend strongly on the properties of each single track and each single layer. In this study, effects of the processing parameters such as laser power, scanning speed and powder layer thickness on the single tracks formation are analyzed. It is shown that, by choosing an optimal technological window and appropriate strategy of SLM, it is possible to manufacture highly complex parts with mechanical properties comparable to those of wrought material.

Peculiar features of electrical resistivity and phase structure in 3-D porous nitinol after selective laser sintering/melting process

The main goal of this study is the peculiarities of shape memory effect in a porous nickel–titanium (NiTi intermetallic phase referred to as nitinol) fabricated via the selective laser sintering/melting process. The phase and structural transformation behaviour of the intermetallide is characterized by means of the scanning electron microscopy, energy dispersive X-ray and X-ray analysis. The effect of the laser sintering parameters and additional heating on the phase content and the thermal dependence of the electrical resistivity are discussed. Peaks and bulbs of the electrical resistivity are found to correspond to the start and finish temperatures of the austenite-to-martensite and reverse phase transitions, and this discovery can be useful for the shape memory effect estimation and optimization. Advantages and shortcomings in the application of this porous material as biological microelectromechanical systems are briefly considered.

Parametric analysis of selective laser melting technology

Technology of selective laser sintering / melting (SLS/SLM) is applied for manufacturing of net shaped objects from different powders : Inox 904L, Ni625, Cu/Sn, W. Experiments were carried out on PHENIX-100 machine : 50 W fibre laser, powder is spread by a roller over the surface of a build cylinder with 100 mm diameter.Width of laser sintered line from Inox 904L powder (powder layer thickness is 50 µm) on metallic substrate was studied applying different laser power P and beam velocity V (V=60-240mm/s) but keeping effective energy input constant P1/ V1∼P2/ V2. Accuracy of fabrication of thin walls and triangles applying different laser power and sintering velocity was studied. Critical beam velocity is defined when sintered lines start to be discontinuous and drops are produced.Different sintering strategies were applied and compared : (a) four different orientations of “vector” of beam displacement relatively given geometry of an object to be manufactured, (b) variation of distance between scanning lines, (c) application of different strategies to fabricate internal and external parts of an object. Performance and limitations of different strategies are analysed applying the following criteria : geometrical accuracy of fabrication, porosity, microhardness. Long term stability of SLM process was controlled by fabrication of thin walled objects during 36 hours. Finally the developed technology was applied for fabrication of parts for mechanical (mini pomp), medical (dental prosthesis, implants ?), bio-medical (diagnostic equipment) applications.The last part of the work was oriented for manufacturing of multi-material products. Two-component products (Stainless steel /Cu) with good material interface were fabricated in a two-step manufacturing cycle.Technology of selective laser sintering / melting (SLS/SLM) is applied for manufacturing of net shaped objects from different powders : Inox 904L, Ni625, Cu/Sn, W. Experiments were carried out on PHENIX-100 machine : 50 W fibre laser, powder is spread by a roller over the surface of a build cylinder with 100 mm diameter.Width of laser sintered line from Inox 904L powder (powder layer thickness is 50 µm) on metallic substrate was studied applying different laser power P and beam velocity V (V=60-240mm/s) but keeping effective energy input constant P1/ V1∼P2/ V2. Accuracy of fabrication of thin walls and triangles applying different laser power and sintering velocity was studied. Critical beam velocity is defined when sintered lines start to be discontinuous and drops are produced.Different sintering strategies were applied and compared : (a) four different orientations of “vector” of beam displacement relatively given geometry of an object to be manufactured, (b) variation of distance between scanning line...

Layer-by-layer laser synthesis of Cu–Al–Ni intermetallic compounds and shape memory effect

We have studied conditions for the synthesis of intermetallic phases in the Cu–Al–Ni system by selective laser sintering/melting, in particular by heating a powder mixture to 300°C. The effects of laser synthesis and heating on the microstructure of the intermetallic phases in the samples obtained have been studied using electron microscopy, optical metallography, and X-ray diffraction analysis. The results demonstrate high sinterability of stoichiometric mixtures. Resistivity measurements indicate that the samples exhibit a shape memory effect. We discuss the feasibility of producing biomicroelectromechanical systems using layerby- layer synthesis.