Dataset for residual stress measurements via neutron diffraction of thermally sprayed Inconel 625 coating on 304 stainless steel.

Fundamental understanding of factors and mechanisms controlling the residual stress formation in material coatings is critical for selection of optimum synthesis and deposition parameters. This article contains data from the investigation of the residual stress properties of Inconel 625 coating measured at different coating thicknesses, 250 µm,300 µm, 350 µm and 400 µm, deposited on 304 stainless steel (SS) substrate using high-velocity oxy-fuel (HVOF) spraying technique. The neutron diffraction technique was employed to measure the residual stresses of the coated specimen. Data provided provides insights into the influence of coating thickness on the residual stress of the material and therefore on the overall mechanical performance and applicability of the component.

Additive manufacturing of alloys with programmable microstructure and properties.

In metallurgy, mechanical deformation is essential to engineer the microstructure of metals and to tailor their mechanical properties. However, this practice is inapplicable to near-net-shape metal parts produced by additive manufacturing (AM), since it would irremediably compromise their carefully designed geometries. In this work, we show how to circumvent this limitation by controlling the dislocation density and thermal stability of a steel alloy produced by laser powder bed fusion (LPBF) technology. We show that by manipulating the alloy's solidification structure, we can 'program' recrystallization upon heat treatment without using mechanical deformation. When employed site-specifically, our strategy enables designing and creating complex microstructure architectures that combine recrystallized and non-recrystallized regions with different microstructural features and properties. We show how this heterogeneity may be conducive to materials with superior performance compared to those with monolithic microstructure. Our work inspires the design of high-performance metal parts with artificially engineered microstructures by AM.

Texture-based residual stress analysis of laser powder bed fused Inconel 718 parts.

Although layer-based additive manufacturing methods such as laser powder bed fusion (PBF-LB) offer an immense geometrical freedom in design, they are typically subject to a build-up of internal stress (i.e. thermal stress) during manufacturing. As a consequence, significant residual stress (RS) is retained in the final part as a footprint of these internal stresses. Furthermore, localized melting and solidification inherently induce columnar-type grain growth accompanied by crystallographic texture. Although diffraction-based methods are commonly used to determine the RS distribution in PBF-LB parts, such features pose metrological challenges in their application. In theory, preferred grain orientation invalidates the hypothesis of isotropic material behavior underlying the common methods to determine RS. In this work, more refined methods are employed to determine RS in PBF-LB/M/IN718 prisms, based on crystallographic texture data. In fact, the employment of direction-dependent elastic constants (i.e. stress factors) for the calculation of RS results in insignificant differences from conventional approaches based on the hypothesis of isotropic mechanical properties. It can be concluded that this result is directly linked to the fact that the {311} lattice planes typically used for RS analysis in nickel-based alloys have high multiplicity and less strong texture intensities compared with other lattice planes. It is also found that the length of the laser scan vectors determines the surface RS distribution in prisms prior to their removal from the baseplate. On removal from the baseplate the surface RS considerably relaxes and/or redistributes; a combination of the geometry and the scanning strategy dictates the sub-surface RS distribution.

Influence of WC Particle Size on the Mechanical Properties and Residual Stress of HVOF Thermally Sprayed WC-10Co-4Cr Coatings.

Cermet coatings deposited using high-velocity oxy-fuel (HVOF) are widely used due to their excellent wear and corrosion resistance. The new agglomeration-rapid sintering method is an excellent candidate for the preparation of WC-Co-Cr feedstock powders. In this study, four different WC-10Co-4Cr feedstock powders containing WC particles of different sizes were prepared by the new agglomeration-rapid sintering method and deposited on steel substrates using the HVOF technique. The microstructures and mechanical properties of the coatings were investigated using scanning electron microscopy, X-ray diffraction, nanoindentation, and Vickers indentation. The through-thickness residual stress profiles of the coatings and substrate materials were determined using neutron diffraction. We found that the microstructures and mechanical properties of the coatings were strongly dependent on the WC particle size. Decarburization and anisotropic mechanical behaviors were exhibited in the coatings, especially in the nanostructured coating. The coatings containing nano- and medium-sized WC particles were dense and uniform, with a high Young's modulus and hardness and the highest fracture toughness among the four coatings. As the WC particle size increased, the compressive stress in the coating increased considerably. Knowledge of these relationships enables the optimization of feedstock powder design to achieve superior mechanical performance of coatings in the future.

Elucidating the relationship between nanoparticle morphology, nuclear/magnetic texture and magnetic performance of sintered SrFe12O19 magnets.

Several M-type SrFe12O19 nanoparticle samples with different morphologies have been synthesized by different hydrothermal and sol-gel synthesis methods. Combined Rietveld refinements of neutron and X-ray powder diffraction data with a constrained structural model reveal a clear correlation between crystallite size and long-range magnetic order, which influences the macroscopic magnetic properties of the sample. The tailor-made powder samples were compacted into dense bulk magnets (>90% of the theoretical density) by spark plasma sintering (SPS). Powder diffraction as well as X-ray and neutron pole figure measurements and analyses have been carried out on the compacted specimens in order to characterize the nuclear (structural) and magnetic alignment of the crystallites within the dense magnets. The obtained results, combined with macroscopic magnetic measurements, reveal a direct influence of the nanoparticle morphology on the self-induced texture, crystallite growth during compaction and macroscopic magnetic performance. An increasing diameter-to-thickness aspect ratio of the platelet-like nanoparticles leads to increasing degree of crystallite alignment achieved by SPS. Consequently, magnetically aligned, highly dense magnets with excellent magnetic performance (30(3) kJ m-3) are obtained solely by nanostructuring means, without application of an external magnetic field before or during compaction. The demonstrated control over nanoparticle morphology and, in turn, crystal and magnetic texture is a key step on the way to designing nanostructured hexaferrite magnets with optimized performance.

Evaluation of residual stress and texture in isotope based Mg11B2 superconductor using neutron diffraction.

Magnesium diboride (MgB2) superconducting wires have demonstrated commercial potential to replace niobium-titanium (NbTi) in terms of comparable critical current density. Its higher critical temperature makes MgB2 wire suitable for liquid-helium-free operation. We recently reported boron-11 isotope-based low-activation Mg11B2 superconducting wire with decent critical current density appropriate for low-cost superconducting fusion magnets. In this study, we have mainly focused on the neutron diffraction technique to measure the residual stress in Mg11B2 superconducting wire for the first time. The residual stress state was given qualitative and quantitative interpretation in terms of micro- and macrostress generation mechanisms based on the isotropic model confirmed by neutron texture measurements. The relationship between the stress/strain state in the wire and the transport critical current density is also discussed. This investigation could pave the way to further enhancement of the critical current density of low-activation Mg11B2 superconducting wires suitable for next-generation fusion grade magnets.

Improvement in the transport critical current density and microstructure of isotopic Mg11B2 monofilament wires by optimizing the sintering temperature.

Superconducting wires are widely used in fabricating magnetic coils in fusion reactors. In consideration of the stability of 11B against neutron irradiation and lower induced radio-activation properties, MgB2 superconductor with 11B serving as boron source is an alternative candidate to be used in fusion reactor with severe irradiation environment. In present work, a batch of monofilament isotopic Mg11B2 wires with amorphous 11B powder as precursor were fabricated using powder-in-tube (PIT) process at different sintering temperature, and the evolution of their microstructure and corresponding superconducting properties was systemically investigated. Accordingly, the best transport critical current density (Jc) = 2 × 104 A/cm2 was obtained at 4.2 K and 5 T, which is even comparable to multi-filament Mg11B2 isotope wires reported in other work. Surprisingly, transport Jc vanished in our wire which was heat-treated at excessively high temperature (800 °C). Combined with microstructure observation, it was found that lots of big interconnected microcracks and voids that can isolate the MgB2 grains formed in this whole sample, resulting in significant deterioration in inter-grain connectivity. The results can be a constructive guide in fabricating Mg11B2 wires to be used as magnet coils in fusion reactor systems such as ITER-type tokamak magnet.