A critical review of powder-based additive manufacturing of ferrous alloys: Process parameters, microstructure and mechanical properties

Highly efficient and low-cost electrocatalysts are essential for water spitting via electrolysis in an economically viable fashion. However, the best catalytic performance is found with noble metal-based electrocatalysts, which presents a formidable obstacle for the commercial success of electrolytic water splitting-based H2 production due to their relatively high cost and scarcity. Therefore, the development of alternative inexpensive earth-abundant electrode materials with excellent electrocatalytic properties is of great urgency. In general, efficient electrocatalysts must possess several key characteristics such as low overpotential, good electrocatalytic activity, high stability, and low production costs. Direct synthesis of nanostructured catalysts on a conducting substrate may potentially improve the performance of the resultant electrocatalysts because of their high catalytic surface areas and the synergistic effect between the electrocatalyst and the conductive substrate. In this regard, three dimensional (3D) nickel foams have been advantageously utilized as electrode substrates as they offer a large active surface area and a highly conductive continuous porous 3D network. In this review, we discuss the most recent developments in nanostructured materials directly synthesized on 3D nickel foam as potential electrode candidates for electrochemical water electrolysis, namely, the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). We also provide perspectives and outlooks for catalysts grown directly on 3D conducting substrates for future sustainable energy technologies.

Nanostructured materials on 3D nickel foam as electrocatalysts for water splitting

This work gives an overview of the production, properties and industrial applications of metal foams. First, it classifies the most relevant manufacturing routes and methods. Then, it reviews the most important properties, with special interest in the mechanical and functional aspects, but also taking into account costs and feasibility considerations. These properties are the motivation and basis of related applications. Finally, a summary of the most relevant applications showing a large number of actual examples is presented. Concluding, we can forecast a slow, but continuous growth of this industrial sector.

Commercial Applications of Metal Foams: Their Properties and Production

Binder jet 3D printing—Process parameters, materials, properties, modeling, and challenges

Additive manufacturing (AM) is a new paradigm for the design and production of high-performance components for aerospace, medical, energy, and automotive applications. This review will exclusively cover directed energy deposition (DED)-AM, with a focus on the deposition of powder-feed based metal and alloy systems. This paper provides a comprehensive review on the classification of DED systems, process variables, process physics, modelling efforts, common defects, mechanical properties of DED parts, and quality control methods. To provide a practical framework to print different materials using DED, a process map using the linear heat input and powder feed rate as variables is constructed. Based on the process map, three different areas that are not optimized for DED are identified. These areas correspond to the formation of a lack of fusion, keyholing, and mixed mode porosity in the printed parts. In the final part of the paper, emerging applications of DED from repairing damaged parts to bulk combinatorial alloys design are discussed. This paper concludes with recommendations for future research in order to transform the technology from “form” to “function,” which can provide significant potential benefits to different industries.

https://www.mdpi.com/2079-6412/9/7/418/pdf

State of the Art in Directed Energy Deposition: From Additive Manufacturing to Materials Design

In this paper, the capability of the CVD technique to produce uniform foams of different properties, with cell size ranging from ∼ 450 to ∼ 3200 μm, porosity from ∼ 70 to ∼ 98 %, and nominal thickness up to 3 mm is presented. In addition to the established application as a battery electrode material, some other potential capabilities and applications are explored.

CVD Technique for Inco Nickel Foam Production

The invention provides a nickel foam and a method of forming a nickel foam for a nickel containing battery. An open-cell foam structure is placed in a nickel carbonyl gas containing structure. The foam structure is heated to a temperature at which nickel carbonyl decomposes. Nickel from the nickel carbonyl gas decomposes on the foam structure to form a nickel plated foam structure. The nickel plated foam structure is then sintered leaving an open-cell nickel network to form the nickel foam. The open-cells of the nickel foam comprise substantially hollow wires having a substantially uniform transverse cross-section. The nickel foam is further characterized by the conductivity through the nickel foam multiplied by a factor of 3.4 being equal to or greater than the theoretical conductivity of nickel.

Method of forming nickel foam

Strength and ductility of as-plated and sintered CVD nickel foams

The laser powder bed fusion (L-PBF) technology was adapted for use with non-spherical low-cost water-atomized iron powders. A simplified numerical and experimental modeling approach was applied to determine—in a first approximation—the operation window for the selected powder in terms of laser power, scanning speed, hatching space, and layer thickness. The operation window, delimited by a build rate ranging from 4 to 25 cm3/h, and a volumetric energy density ranging from 50 to 190 J/mm3, was subsequently optimized to improve the density, the mechanical properties, and the surface roughness of the manufactured specimens. Standard L-PBF-built specimens were subjected to microstructural (porosity, grain size) and metrological (accuracy, shrinkage, minimum wall thickness, surface roughness) analyses and mechanical testing (three-point bending and tensile tests). The results of the microstructural, metrological and mechanical characterizations of the L-PBF-built specimens subjected to stress relieve annealing and hot isostatic pressing were then compared with those obtained with conventional pressing-sintering technology. Finally, by using an energy density of 70 J/mm3 and a build rate of 9 cm3/h, it was possible to manufacture 99.8%-dense specimens with an ultimate strength of 330 MPa and an elongation to failure of 30%, despite the relatively poor circularity of the powder used.

https://www.mdpi.com/2504-4494/1/2/23/pdf

Laser powder bed fusion of water-atomized iron-based powders: process optimization

Although iron, as a basic metal, has been used commonly in industry, the use of an advanced technique such as additive manufacturing (AM) may offer more opportunities. For example, AM of iron-based powders for functional prototypes would likely be beneficial in the automotive industry, since this industry has commonly used iron alloys for prototypes and functional parts produced by conventional technologies. This paper presents Laser Directed Energy Deposition through Powder Feeding (LDED-PF), a class of AM, of irregular-shape inexpensive water-atomized iron powder. A setup with a lateral powder-fed nozzle was deployed to deposit single-tracks using different processing parameters. The experimental design and optimization model were implemented based on the response surface methodology when the regression model was tested by the variance analysis. The desirability function was used to identify the optimal processing window to obtain the single-tracks with a minimized dilution and a maximized bead height and high powder efficiency. The results showed that the geometrical characteristics of the single-tracks have a high dependency on the key LDED-PF processing parameters. In addition, the microstructure and phase composition of the single-tracks were investigated by SEM and EDS, revealing that the deposits were generally composed of the ferrite phase.

Vladimir Paserin

Papers

CVD Technique for Inco Nickel Foam Production

Method of forming nickel foam

Strength and ductility of as-plated and sintered CVD nickel foams

Laser powder bed fusion of water-atomized iron-based powders: process optimization

Laser directed energy deposition of water-atomized iron powder: Process optimization and microstructure of single-tracks