Selective electron beam melting (EBM) is a powder-bed based additive manufacturing technique for the fabrication of dense metallic parts. As a free-form deposition process EBM offers a high degree of freedom in design and a highly efficient utilization of material. For a widespread industrial application the achievable build rate is a critical factor. In this paper the process window for Ti-6Al-4V is explored by varying beam current and scan speed in a wide range. The EBM specimens were characterized by their density, porosity size and distribution, chemical composition, microstructure, hardness and tensile strength. Key findings include: (1) the minimum line energy necessary to achieve full density, (2) parameter sets for increased build rates at full density, and (3) formation of α'-martensite at high scan rates.

Additive manufacturing (AM) of metals is stimulating the tool making industry. Moreover, besides the production of lost forms, AM processes are now being used to directly generate tools, molds or parts, leading to massive time savings. In the case of material development for AM, the challenge is to operate with carbon-containing iron-based materials distinguished by high strength and hardness, as well as high corrosion resistance and thermal conductivity. Often, those materials are susceptible to crack formation during processing. Using Electron Beam Powder Bed Fusion (PBF-EB), the challenge of crack formation can be overcome by using high process temperatures in the range 800–900 °C. In this paper, results on the processing of a cold-working tool steel (X65MoCrWV3-2) and a hot-working steel (X37CrMoV5-1) will be presented. These include the processing window, processing strategies to minimize the density of cracks and properties with respect to microstructure and hardness.

Due to the small variety of materials, the areas of application of additive manufacturing in the toolmaking industry are currently still limited. In order to overcome these material restrictions, AM material development for high carbon-containing iron-based materials, which are characterized by high strength, hardness, and wear resistance, must be intensified. However, these materials are often susceptible to crack formation or lack of fusion defects during processing. Therefore, these materials are preferentially suited for electron beam powder bed fusion (PBF-EB). In this paper, an Fe-Cr-V alloy with 10% vanadium is presented. Investigations were carried out on the PBF-EB system Arcam A2X. Specimens and demonstrators are characterized by a three-phase microstructure with an Fe-rich matrix and VC and M₇C₃ reinforcements. The resulting microstructures were characterized by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Furthermore, mechanical and physical properties were measured. A final field test was conducted to evaluate durability in use.

Current metal additive manufacturing (AM) technologies imply complicated processes, with many variable parameters determining their performance and the quality of the resulting product. Process optimisation requires feedback from nondestructive evaluation (NDE) of the additively manufactured parts. The presence of a complicated internal structure and complex shapes and geometries are limiting factors in the application of standard, preferably online, NDE techniques for quantitative assessment of process-related defects such as irregular internal structure, porosity, etc. In this study, potential non-linear elastic wave spectroscopy (NEWS) methods were tested to classify two types of artificially created defect in Ti-6Al-4V prismatic samples fabricated by an electron beam melting (EBM) system. Two series of samples with variable internal defects were tested: samples with central circular defects (missing material gaps) and samples with gradually growing stochastic porosity. Each group of samples also contained a fully compact sample for comparison. Additional ultrasonic NEWS procedures were then tested to classify the variability of defects. A relatively simple experimental facility with two piezoelectric transducers allowed samples to be analysed and the results recorded. The best results, documented in this paper, were obtained using two modifications of the non-linear wave modulation spectroscopy (NWMS) procedure. One group was successfully classified with two mixed excitation frequencies; slopes of amplitude-dependent inter-modulation sidebands identified samples with growing defect thickness. For the second group, longer chirp excitation was used mixed with signals of constant frequency and/or without any mixing. Growing dispersed stochastic porosity was successfully classified using these methods. The results of NEWS tests indicate that selected NEWS procedures can also be used for online AM monitoring.

In the present state of the art, highly spherical alloy powders are employed as feedstock in powder bed fusion processes. These powders are characterized by high flowability and apparent density. Their elaborate fabrication process is reflected in high powder price, adding a significant fraction to the cost of additively manufactured parts. Thus, the use of non-spherical powders, such as water atomized material, can lower costs significantly. Here, the electron beam powder bed fusion (PBF-EB) of standard water atomized iron powder used for press-and-sinter is studied. Despite raking problems, using the coating mechanism in standard configuration samples with densities exceeding 99% were fabricated. In a further step, the addition of alloying elements by powder blending is explored. Important powder properties of feedstock blended from irregular and spherical powders are characterized. The PBF-EB processing of two alloys is presented. The first represents a low carbon steel. Samples were characterized by metallographic cross-section, energy dispersive X-ray (EDX) mapping, and mechanical testing. The second alloy system is a FeCrAl. After PBF-EB processing of the powder mixture, chemical homogeneity was achieved. Besides the low cost, this approach of using water atomized powder mixed with master alloy offers the advantage of high flexibility for potential application.

Manufacturing of Net-Shape and Wear-Resistant Composite Components via the Combination of Additive Manufacturing and Hot Isostatic Pressing Markus Mirz, Mar