Key Engineering Materials Vol. 799

Abstract: The goal of this work was to investigate microstructure of the selective laser sintering (SLS) produced parts evaluating effect of powder type and fraction size. Studies have shown that printed samples of 316L and GP1 metal powders had a higher defect content compared to printed components from MP1 powder material. From scanning electron microscopy (SEM), it was found that iron-based printed parts melted worse than Co-Cr alloy components. Iron-based 316L and GP1 metal powders did not get enough energy from laser to perform a better microwelding between particles. Surface roughness Ra numerical values for samples 316L, GP1, MP1 respectively are Ra = 13.7 μm; 11.4 μm; 3.0 μm. Stainless steel powder material contains particles which size varies between 20 – 120 μm. The Co-Cr alloy and the maraging steel powder materials are made of 10 – 80 μm particles. The chemical and elemental composition of powder materials were examined using SEM-EDS technology.

Abstract: Titanium has been evaluated in a broad range of aerospace, biomedical and sports equipment applications due to its unique combination of high mechanical strength, light weight and good biocompatibility. However, Ti implants are often subject to wear in specific areas. Therefore, the improvement of mechanical properties, such as hardness, wear resistance, bearing capability of implants is a key point to broaden the application fields of titanium. Cubic boron nitride (cBN) is a well-known superhard material possessing high chemical stability and biocompatibility. However, cBN suffers from poor machinability and sinterability. Attempts to process boron nitride by laser treatment into intricate shapes are extremely difficult, expensive and time-consuming tasks squeezing its applicability. In this work, manufacturing of Ti/cBN cellular structures and solid parts of high strength and good wear resistance by selective laser melting was performed. In Ti/cBN composite powder, the boron nitride provides the excellent mechanical properties, and titanium promotes the laser absorption improving the process of densification. The parametric study of consolidation process has been performed and the microstructural features along with mechanical properties are examined.

Abstract: This article presents the analysis and redesign of an equipment aimed at repairing in-situ the journal surface of a marine diesel engine crankshaft, based on laser cladding technology. The paper outlines the comprehensive research conducted to study the device, identify its weaknesses and establish a strategy to improve it. To address this task, we shall describe (i) a study of the working environment, (ii) performance of functional analysis using computer-aided engineering tools and finite element analysis of the current prototype, (iii) a study of the results and identification of problematic areas, (iv) proposed improvements based on the results, (v) the presentation of a 3D model with the proposed improvements.

Abstract: Additive manufacturing (AM) technology has the potential to revolutionize multiple fields of industry Defect formation is a common problem in all AM processes. For the applicability of this technology for manufacturing electrical machines, specific mechanical and electromagnetic properties of printed material are necessary. In this paper we present a literature review on the effects of production parameters on the printed material properties, alongside experimental results of printed electrical steel sample properties with default processing parameters.

Abstract: Additive Manufacturing is a manufacturing process based on layers for making three dimensional scaled physical parts directly from 3D CAD data. Fused Deposition Modeling (FDM) is widely used technology that provides functional prototypes in various thermoplastics. In additive manufacturing, filling patterns are of two types; External and Internal filling patterns. Multiple patterns are developed for both filling categories. In this work, a heterogeneous infill strategy is used by choosing developed patterns in order to improve strength to weight ratio, material usage and build time for parts. A rectilinear pattern combination with triangular and rectangular pattern has been chosen for 3D printing. The tensile testing is performed on the printed specimens to calculate the strength to weight ratio. By comparing the obtained results, a strategy based on maximum strength to weight ratio, minimum material usage and reduced build time is recommended for FDM technology.

Abstract: This paper presents the theoretical analysis and experimental results concerning the rheological behavior and mix design of a 3d printable cement paste as matrix for printing concrete. From the point of view of classical rheology of disperse systems, the application of 3D printing technology in construction has been analyzed. The general scientific concept for optimization of admixtures for 3D printable materials has been developed in terms of viscosity, consistency, and parameters of flocculation and structural built-up. The technological tools to control rheological behavior of visco-plastic admixtures are identified in all stages of 3D printing such as mixing, pumping, extrusion, multilayer casting and structural built-up in the printing layers. The relevant considerations include the concentration, size, morphology, chemical and mineralogical composition, the physical and chemical activity of the solid phase’s surface, and the ionic composition, viscosity, and density of the liquid phase. The squeezing test is used in this paper as a rheological behaviour identification tool of cement-based materials in order to evaluate the extrudability and buildability. It is shown that these properties are significantly influenced by the mix proportions such as W/C-ratio, concentration of plasticizer additives and viscosity modifier additives as factors of changes in the concentration of the dispersed phase and properties of the dispersion liquid.

Abstract: 3D Printing can be considered as one of the most innovative manufacturing processes of our time. Part of the innovative potential of 3D Printing is associated with the production of geometrically complex parts in a relatively short time. In the present paper, a methodology for the production of parts with complex internal structure and intra-layer density variability (ILDV) is presented. The proposed methodology may be used to produce structures composed by two materials, such as functionally graded parts and composites. The variability of the internal structure and composition is captured through voxel modeling, where at each voxel a unique relative density value for each material is assigned. These relative density values are then translated to predefined extrusion paths, which the 3D printer follows for the construction of layers composed by one or two materials. Representative cases and examples of parts with ILDV are presented and discussed.

Abstract: Electron beam (EBAM) and laser beam (LBAM) additive manufacturing processes with a deposited material in the form of a wire are an efficient methods enabling the making of component parts. The scope of the presented work was to investigate the influence of technological process on microstructure and mechanical properties such as tensile strength, microhardness and elongation of the fabricated components. The achieved results and gained knowledge will enable the production of a whole structure from stainless steel in the future. The metallographic examination revealed that the microstructure is not fully homogenies, the cell-dendritic areas occurred. Moreover, the microhardness profiles indicated that some fluctuation in the microstructure as well as mechanical properties can be observed on the cross section of deposited components. However, the mechanical tests showed that the tensile strength as well as elongation fulfil the requirement of producer of deposited wire.