Dynamic Behaviour of Selective Laser Melted 316L Steel - Mechanical Properties and Microstructure Changes

316L steel specimens with three different shear zones made by SLM (Selective Laser Melting) were subjected to dynamic tests using the Split Hopkinson Pressure Bar method. The effect of high-speed deformation on changes in microstructure was analyzed. In addition, the stress-strain relationship was determined from the SHPB results. To visualize the deformation process of the specimens during the tests, a camera with a high frame rate was used. It was shown that as the plastic deformation increases, the hardness of the material increases. Microstructural analysis of dynamically loaded areas revealed numerous defects. Twinning was found to be the main deformation mechanism. Large plastic deformation and many other microstructural changes such as shear bands, cracks and martensite nucleation were also observed

THE INFLUENCE OF FRICTION STIR WELDED PROCESS PARAMETERS OF AA2519-T62 ON JOINT QUALITY DEFINED BY NON-DESTRUCTIVE LASER AMPLIFIED ULTRASONIC METHOD AND BY MICROSTRUCTURE ANALYSIS

The presented research contains a description of a non-destructive laser ultrasound internal structure analysis of aluminium joints made by friction stir welding. In the research, four selected technological parameter groups were taken into account. Modifications used in different parameter groups included changing tool traverse speeds and also its rotation speeds. The most important goal of this research was to determine the joint quality using a non-destructive laser amplified ultrasound method  To verify obtained test results, an additional microstructural analysis was also conducted

The Examination of Restrained Joints Created in the Process of Multi-Material FFF Additive Manufacturing Technology

The paper is focused on the examination of the internal quality of joints created in a multi-material additive manufacturing process. The main part of the work focuses on experimental production and non-destructive testing of restrained joints of modified PLA (polylactic acid) and ABS (Acrylonitrile butadiene styrene) three-dimensional (3D)-printed on RepRap 3D device that works on the “open source” principle. The article presents the outcomes of a non-destructive materials test in the form of the data from the Laser Amplified Ultrasonography, microscopic observations of the joints area and tensile tests of the specially designed samples. The samples with designed joints were additively manufactured of two materials: Specially blended PLA (Market name—PLA Tough) and conventionally made ABS. The tests are mainly focused on the determination of the quality of material connection in the joints area. Based on the results obtained, the samples made of two materials were compared in the end to establish which produced material joint is stronger and have a lower amount of defects

The Influence of Exposure Energy Density on Porosity and Microhardness of the SLM Additive Manufactured Elements

Selective laser melting (SLM) is an additive manufacturing technique. It allows elements with very complex geometry to be produced using metallic powders. A geometry of manufacturing elements is based only on 3D computer-aided design (CAD) data. The metal powder is melted selectively layer by layer using an ytterbium laser. This paper contains the results of porosity and microhardness analysis made on specimens manufactured during a specially prepared process. Final analysis helped to discover connections between changing hatching distance, exposure speed and porosity. There were no significant differences in microhardness and porosity measurement results in the planes perpendicular and parallel to the machine building platform surface

Koncepcja przeprowadzenia próby skręcania elementów ze stali 20CrNiMo2-2 wytworzonych z zastosowaniem technik przyrostowych

In recent years, additive manufacturing (AM) technologies, have been one of the fastest developing methods of production of various components. As far as building material is concerned, they allow for using not only polymers, but also composites or metals. Products fabricated using said technologies are used in various areas of industries, for instance in medicine, architecture, entertainment, and in particular in the construction of parts and components of machinery and equipment. To recognize and determine the products’ strength properties in a more comprehensive manner, 3D printing products used in mechanical applications are subject to various tests, e.g. static tensile test. This paper contains research about static torsion test on cylindrical samples made of high grade 20CrNiMo2-2 steel using the selective laser melting (SLM). Such an approach allowed to observe the material behaviour and to determine specific values of strength properties, such as the maximum tangential stresses in the material and bulk modulus of elasticity (shear modulus). The determination of such parameters allowed to compare them with the results of the tests carried out on components manufactured using other methods (e.g. a cold drawn solid bar sample).W ostatnich latach przyrostowe techniki wytwarzania, a w szczególności druk 3D, są jednymi z najszybciej rozwijających się metod produkcji różnych elementów. Pozwalają one na wykorzystanie jako materiału budulcowego nie tylko polimerów, ale również kompozytów czy metali. Produkty powstałe z zastosowaniem opisywanych technik znajdują zastosowanie w różnych dziedzinach życia, dla przykładu w medycynie, architekturze, rozrywce a w szczególności w budowie części i elementów maszyn i urządzeń. Aby lepiej poznać i określić właściwości wytrzymałościowe wyrobów, kluczowe w przypadku wykorzystania produktów druku 3D w dziedzinie mechanicznej, poddaje się je wielu badaniom np. statycznej próbie rozciągania. Rozważanym pomysłem jest przeprowadzenie statycznej próby skręcania walcowych próbek wytworzonych z wysoko-gatunkowej stali 20CrNiMo2-2 z zastosowaniem techniki selektywnego spiekania proszku metalu (SLM). Pozwoli ono na obserwację zachowania się materiału oraz wyznaczenie konkretnych wartości właściwości wytrzymałościowych, takich jak maksymalne naprężenia styczne występujące w materiale oraz moduł sprężystości poprzecznej (modułu Kirchoffa). Dzięki ich znajomości możliwym będzie porównanie ich z wynikami badań przeprowadzanych nad elementami wytwarzanymi w inny sposób (np. próbka z litego pręta ciągnionego)

Performance Analysis of Additively Manufactured Hydraulic Check Valves with Different Postprocessing

Due to the need to use very precise manufacturing processes, hydraulic applications are one of the most demanding parts in production. Such a feature requires using molded and properly machined parts. On the other hand, such an approach makes hydraulic parts very heavy and requires the use of large amounts of material. One of the most promising manufacturing technologies that could be a real alternative to hydraulic parts production is additive manufacturing (AM). This paper aims to study how the AM process affects the performance properties of the as-built state, and investigate changes after different types of postprocessing in the case of hydraulic check valves. Based on the obtained results, using proper postprocessing is a crucial feature of obtaining check valves that perform their functions in a hydraulic system. In as-built parts, the surface roughness of the valve seats significantly exceeds the acceptable range (almost nine times—from 4.01 µm to 33.92 µm). The influence of the surface roughness of the valve seats was verified via opening pressure and internal leakage tests based on ISO standards. The opening pressures in all tested samples were similar to those in the conventionally made counterparts, but in the case of internal leakage only a fully finished AM valve revealed promising results. The obtained results could be useful for various enterprises that are seeking weight reduction possibilities for their low-volume manufactured products

Modification of Structural Properties Using Process Parameters and Surface Treatment of Monolithic and Thin-Walled Parts Obtained by Selective Laser Melting

Additive manufacturing is one of the most popular technological processes and is being considered in many research works, a lot of which are related to thin-walled parts analysis. There are many cases where different part geometries were manufactured using the same process parameters. That kind of approach often causes different porosity and surface roughness values in the geometry of each produced part. In this work, the porosity of thin-walled and monolithic parts was compared. To analyze additively manufactured samples, porosity and microstructural analyses were done. Additionally, to check the influence of process parameter modification on the manufactured parts’ properties, hardness and roughness measurements were made. Surface roughness and the influence of surface treatment were also taken into account. Porosity reduction of thin-walled parts with energy density growth was observed. Additionally, a positive influence of slight energy density growth on the surface roughness of produced parts was registered. Comparing two extreme-parameter groups, it was observed that a 56% energy density increase caused an almost 85% decrease in porosity and a 45% increase in surface roughness. Additional surface treatment of the material allowed for a 70–90% roughness reduction

Mechanical Properties Analysis of the AA2519-AA1050-Ti6Al4V Explosive Welded Laminate

Explosively welded layered materials made of (a) an AA2519 aluminum alloy (AlCuMgMn + ZrSc), (b) titanium alloy Ti6Al4V and (c) an intermediate layer composed of a thin aluminum alloyed AA1050 layer are considered herein. This study presents test results connected to measurement science including microstructural observations of the material combined with the explosive method, and a basic analysis of the strength properties based on microhardness and tensile tests. Owing to the joint’s special manufacturing conditions, the laminate was subjected to deformation measurements with the digital image correlation (DIC) method. The research was supplemented by the residual stress measurements with the sin2ψ X-ray method based on the diffraction–reflection analysis that was verified by the bore trepanation method

Processability of 21NiCrMo2 Steel Using the Laser Powder Bed Fusion: Selection of Process Parameters and Resulting Mechanical Properties

With the development and popularization of additive manufacturing, attempts have been made to implement this technology into the production processes of machine parts, including gears. In the case of the additive manufacturing of gears, the availability of dedicated materials for this type of application is low. This paper summarizes the results of research on the implementation of 21NiCrMo2 low-alloy steel, which is conventionally used to produce gears as a feedstock in the PBF-LB/M process. The work presents research on the selection of process parameters based on porosity measurements, static tensile tests, and hardness measurements. In addition, the article includes a mathematical model based on the quadratic regression model, which allows the estimation of the percentage of voids in the material depending on the assumed values of independent variables (laser power, scanning velocity, and hatch distance). The paper includes a range of process parameters that enable the production of elements made of 21NiCrMo2 steel with a density of over 99.7%. Additionally, comparative tests were carried out on PBF-LB/M-manufactured steel (in the state after printing and the state after heat treatment) and conventionally manufactured steel in terms of its mechanical and microstructural properties. The results showed that the steel exhibited similar mechanical properties to other carburizing steels (20MnCr5 and 16MnCr5) that have been used to date in PBF-LB/M processes and it can be used as an alternative to these materials