The microstructure and microhardness of the surface layer of annular projections on disks of steel—copper powder pseudoalloy are investigated after laser heat treatment by a 1-kW fiber laser. The...

Additive manufacturing of porous materials with a specific macrostructure and tunable mechanical properties is a state-of-the-art area of material science. Additive technologies are widely used in industry due to numerous advantages, including automation, reproducibility, and freedom of design. Selective laser melting (SLM) is one of the advanced techniques among 3D fabrication methods. It is widely used to produce various medical implants and devices including stents. It should be noticed that there is a lack of information on its application in stent production. The paper presents the technological aspects of CoCr stent SLM fabrication, including design of stents and development of regimes for their manufacturing. Physical, chemical, and technological properties of CoCr powder were initially determined. Parametric design of mesh stent models was adopted. A two-stage approach was developed to ensure dimensional accuracy and quality of stents. The first stage involves a development of the single-track fusion process. The second stage includes the stent manufacturing according to determined technological regimes. The single-track fusion process was simulated to assign laser synthesis parameters for stent fabrication. Melting bath temperature and laser regimes providing such conditions were determined. Twenty-seven SLM manufacturing regimes were realized. Dependence of single-tracks width and height on the laser power, exposition time, and point distance was revealed. The qualitative characteristics of tracks imitating the geometry of the stent struts as well as favorable and unfavorable fusion regimes were determined. The results of surface roughness regulating of the stents’ structural elements by various methods were analyzed. Thus, this two-staged approach can be considered as a fundamental approach for CoCr stent SLM fabrication.

Selective laser melting (SLM) is an additive manufacturing process that involves the layer-by-layer construction of a three-dimensional object by local melting of a powder layer based on a prepared CAD model. This technology makes it possible to manufacture products of complex configuration, including internal channels of complex geometry. Such products include personalized highly porous implants, which are subject to very strict requirements in the field of elastic and strength properties, ensuring their compliance with the properties of the biological objects being replaced. The quality of highly porous cellular products formed by the selective laser melting method based on metal powder compositions is determined by a significant number of factors, the combined influence of which is difficult to control. At the same time, the structure and mechanical properties of highly porous cellular materials (HPCM) obtained by laser synthesis are largely determined by the melt bath shape stability, which depends on the ability of local heat dissipation, which in turn is determined by the fused product geometry. Under these conditions, simulation of thermal processes, including the prediction of the part fusion temperature modes, is of paramount importance. This study focuses on the numerical analysis of the powder layer thermophysical parameters during the laser melting process, which is difficult to analyze by direct measurements, and a computational model based on COMSOL Multiphysics has been created to predict the melt bath temperature field. The numerical model made it possible to quantify the influence of the selective laser melting process parameters (laser power and scanning speed) in combination with the choice of material and topology of the part on the temperature fields formation to determine the process technological parameter and the features of creating geometry for additive manufacturing, which make it possible to obtain products of proper quality. Cellular implants based on Ti6Al4V powder have been grown by selective laser melting.

Селективное лазерное плавление представляет собой процесс аддитивного производства, предполагающий послойное построение трехмерного объекта путем локального плавления слоя порошка на основе подготовленной CAD-модели. Данная технология позволяет изготавливать изделия сложной конфигурации, включающие внутренние каналы сложной геометрии. К такого рода изделиям относятся персонифицированные высокопористые имплантаты, к которым предъявляются весьма жесткие требования в области упругих и прочностных свойств, обеспечивающие их соответствие свойствам заменяемых биологических объектов. Качество высокопористых ячеистых изделий, сформированных методом селективного лазерного плавления на основе металлопорошковых композиций, определяется значительным числом факторов, совокупное влияние которых трудно поддается контролю. При этом структура и механические свойства высокопористых ячеистых материалов, полученных методом лазерного синтеза, в значительной степени определяются стабильностью формы ванны расплава, которая зависит от способности локального отвода тепла, определяемой в свою очередь геометрией сплавляемого изделия. Представленное исследование посвящено численному анализу теплофизических параметров порошкового слоя во время процесса лазерного плавления, которое затруднительно анализировать путем прямых измерений, при этом создана вычислительная модель на основе COMSOL Multiphysics для прогнозирования температурного поля ванны расплава. Численная модель позволила количественно оценить влияние параметров процесса селективного лазерного плавления (мощность лазера и скорость сканирования) в сочетании с выбором материала и топологии детали на формирование температурных полей, определить технологические параметры процесса и особенности создания геометрии для аддитивного производства, позволяющие получать изделия должного качества. Методом лазерного плавления выращены ячеистые имплантаты на основе порошка Ti6Al4V.