Powder-based Technology Research Articles

The effect of building strategies on tensile strength of additively manufactured parts by laser metal deposition

Abstract Laser Metal Deposition (LMD) is a powder-based technology. This technology can be used for surface coating, repairing and additive manufacturing. The property of the part is dependent on the building parameters of the process. In the research work, we use austenitic steel (316L) powder to produce blocks with different building strategies, from which we machine tensile test specimens. The patterns were prepared according to three strategies: the welded bands were parallel to the longitudinal axis of the test specimen, perpendicular to it, and finally the parallel and perpendicular directions were alternated. We perform hardness and tensile tests on these specimens and search for correlations between the strength and the strategies.

Minimizing Porosity in 17-4 PH Stainless Steel Compacts in a Modified Powder Metallurgical Process

Nowadays, powder-based manufacturing processes are recognized as cost-efficient methods frequently employed for producing parts with intricate shapes and tight tolerances in large quantities. However, like any manufacturing method, powder-based technologies also have several disadvantages. One of the most significant issues lies in the degree of porosity. By modifying the morphology of the gas-atomized spherical 17-4PH stainless steel powder via prior ball milling and then raising both the pressure of cold compaction (1.6 GPa) and sintering temperature (1275 °C), the porosity could be reduced considerably. In our novel powder metallurgical (PM) experimental process, an exceptionally high green density of 92% could be reached by employing die wall lubrication instead of internal lubrication and utilizing induction heating for rapid sintering. After sintering (at temperatures of 1200, 1250, and 1275 °C), the samples aged in the H900 condition were then mechanically tested (Charpy impact, HV hardness, and tensile tests) as a function of porosity. Sintering at 1275 °C for one hour enabled porosity reduction to below 4%, resulting in 1200 MPa yield strength and 1350 MPa ultimate tensile strength with significant (16%) fracture strain. These values are comparable to those of the same alloy products fabricated via ingot metallurgy (IM) or additive manufacturing (AM).

Advances in Powder-based Technologies for Production of High-Performance Sputtering Targets

Abstract The sputtering method has been extensively adopted for the production of high-performance thin films and coatings. This can be attributed to its versatility and flexibility, which allows easier tailoring of the properties and characteristics of the sputtered films and coatings for the desired application and performance. Contrary to thermal spray and chemical techniques, sputtering can be performed at room temperature for a wide range of targets, thus overcoming the challenges, such as residual stresses and degradation of the substrates, associated with high-temperature processes. The most important aspect of the sputtering is the target from which the thin film material is derived. The quality of the target determines the properties and performance of the resulting film and coating. Published data reveal that the quality of the targets depends mainly on the method of production. Although different manufacturing techniques have been used to produce these targets, consolidation of powders has been shown to provide outstanding results. The production of these targets through powder metallurgy depends on the compaction or sintering methods and associated processing parameters. With the increasing demand for high-performance thin films and coatings, such as high-entropy alloy films, the quality of the targets used for sputtering is crucial for application in various fields that include medical, electronics, and energy. In this article, progress on the powder metallurgy on the manufacturing of sputtering targets is detailed. Advances in various powder technologies, process parameters, and conditions, and their interrelationships with properties and performance of targets and sputtered thin films will be discussed, synthesized, and general/specific trends will be derived. This article will serve as a resource for metallurgists in the optimization and development of advanced targets for industry 4.0.

Experimental Investigation on the Forming of Additively Manufactured Components with Regard to Forming Behavior and Component Properties

Additive Manufacturing is an established process group that includes various technologies. In contrast to subtractive methods, complex components can be produced by applying layers of construction materials. In accordance with the standard VDI Guideline 3405, additive manufacturing technologies can be differentiated into wire- and powder-based technologies. The basis for these experimental investigations is a Wire Arc Additive Manufacturing (WAAM) process with a high build-up rate (Cold Metal Transfer - CMT) to produce a rectangular thin-walled component made of G4Si1 (1.5130). In order to analyze the influence of a subsequent forming process on the microstructural properties and the forming behavior of the components, compression tests were carried out. Therefore, cylindrical specimens were made out of the additively manufactured components by machining. To be able to take a possible anisotropy in the workpiece caused by the multi-layer welding into account, the samples were taken both along and across the welding direction. To evaluate the inhomogeneous component properties, cast specimens with a representative microstructure were produced by inductive melting of the filler material and subsequent a solidification with an appropriate cooling rate. In addition to the cold forming of the additively manufactured components, the investigation also includes hot forming and the influence of a corresponding heat treatment. The experimental examination was completed by the analysis of the microstructure of each material state.The aim of the research work was to prove the homogenization and optimization of the mechanical properties of additive manufactured components due to a subsequent forming process.

Development of a Coated-Micro-Particle Neutron Detector Based on LiF/ZnS Scintillator

6LiF:ZnS(Ag) micro-particle neutron detectors are a promising technology to further improve neutron detection capabilities for a variety of applications. Specifically, we have been investigating 6LiF micro-particles coated with ZnS(Ag) to increase the neutron detection efficiency, light production, and light collection efficiency when compared to the existing powder-based technology (EJ-426 from Eljen Technology). Extensive radiation and light transport simulations with single micro-particles have been performed to find the optimal 6LiF diameter and ZnS(Ag) coating thickness. Full-scale multi-particle simulations also have been performed to determine the optimal pitch (particle-to-particle distance) and detector thickness. Randomizations of 6LiF radius, ZnS(Ag) coating thickness, position of particles, as well as shape of particles and partial coating have been performed to account for possible manufacturing imperfections. EJ-426 sheets have been modeled for reference purposes by defining spherical grains of 6LiF and ZnS(Ag) and compared against experiments. The simulation results show that the coated micro-particles should dramatically increase the neutron detection efficiency, light production, and light collection efficiency when compared to the existing EJ-426 technology.