High Velocity Oxy-Fuel (HVOF) thermal spraying enables the deposition of dense coatings with low porosity, high hardness, and good fracture resistance. Tungsten carbide-cobalt (WC-Co) coatings are widely used in industrial and aerospace applications due to their excellent wear resistance; however, improving crack resistance and coating-substrate adhesion remains a key challenge. In this study, WC-Co+Ni composite coatings were deposited on ductile cast iron, with emphasis on the role of Ni addition in controlling microstructure development under HVOF conditions. Microstructural characterization was performed using optical, scanning, and transmission electron microscopy (OM, SEM, TEM), while phase composition and chemical analysis were determined by X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS). The coatings exhibited a dense, low-porosity microstructure composed of fine WC and W2C carbides embedded in a Co-Ni binder, with locally nanocrystalline regions. XRD analysis confirmed WC and W2C as the dominant phases, with weak reflections corresponding to the η-phase (Co6W6C), indicating local decarburization. The addition of Ni increases the fraction of the transient liquid phase during particle flight, enhancing carbide dissolution and mass transport in the binder, which accelerates decarburization kinetics and promotes η-phase formation. Simultaneously, Ni modifies the binder into a more ductile Co-Ni matrix, reducing the detrimental effect of brittle η-phase on coating integrity. Mechanical and tribological testing (instrumented indentation and scratch testing) demonstrated improved crack resistance, wear resistance, and adhesion. The results show that Ni addition enables process-driven microstructural tailoring of HVOF-sprayed WC-Co coatings, leading to enhanced performance despite the presence of η-phase.

CT images of castings made of ductile iron were analyzed in the paper. On these images, objects can be identified that can be considered as graphite precipitates or indicate the presence of a defect in the casting. Research conducted in this area is described, based on experimental data that allows to determine whether the indicated components present in the casting are graphite precipitation. Analyzing the results, a conclusion was drawn that the classification based solely on the input data used is insufficient. Such action allowed to obtain information that there are particles in the casting that can be both graphite separation and imperfections (in particular voids, porosities, discontinuities). These results are subjected to further analysis (pictures) to help decide whether the object is a separation or a discontinuity. The available (experimental) data make it possible to unequivocally identify belonging to one of these groups. The use of machine learning methods to recognize the relationships between the physical parameters of particles helps to improve the analysis process. An important aspect was the determination of three ranges in the scale of shades of gray, which were used to determine the labels for the input data. Lighter shades in the first range indicate slight differences in the density of the particle, and thus suggest the occurrence of cast fineness. The middle range corresponding to the darker shades of gray was assigned to particles that could be shrinkage porosities. The darkest shades corresponded to occurrences of gas porosities (voids). Shades of gray cannot be the only determinant of the type of microstructure component, because apart from imperfections, there are also graphite precipitations in the casting (shape and shade of gray resembling emptiness). It cannot be assumed that specific types of defects will occur in the tested object (e.g. only gas porosities), which requires additional analysis of the microstructure image.

This article presents the results of testing the suitability of X-ray computed tomography for the quality control of the casting moulds used for producing turbine blades. The research was focused on the analysis of cross-sectional images, spatial models and the porosity of moulds using a Phoenix L 450 microtomograph. The research material consisted of samples from three mixtures of ceramic materials and binders intended for producing casting moulds using the lost wax method. Various configurations of filling materials (Molochite and quartz flours) and binder (Remasol, Ludox PX 30 and hydrolysed ethyl silicate) mixtures were considered. X-ray computed tomography enabled the detection of a number of defects in the ceramic mass related to the distribution of mass components, porosity concentration and defects resulting from the specificity of the mould production. It was found that casting mould quality control on cross-sectional tomographic images is faster and as accurate as the analysis of three-dimensional models and allows for the detection of a whole range of ceramic defects, but the usefulness of the images is greatest only when the cross-sections are taken at an appropriate angle relative to the object being examined.

Recent studies have highlighted the beneficial role of rhenium in enhancing the properties of superalloys. Even a slight alloying addition of rhenium can lead to a significant improvement in mechanical properties, particularly at elevated temperatures. This finding is particularly intriguing in the context of powder-based additive manufacturing techniques, which enable the utilization of powder mixtures to create metal matrix composites (MMCs) or facilitate in situ alloying. The primary objective of the current research was to examine the impact of rhenium on the powder bed fusion-laser beam (PBF-LB) process of IN 625, a specific alloy. Despite its limited solubility in the as-built state, the addition of rhenium was found to have a notable influence on increasing the ultimate tensile strength (UTS). This effect became even more pronounced after heat treatment (solution treatment), which induced a higher dispersion of rhenium and other precipitates within the material. The experimental results demonstrated that the specimen with the addition of rhenium exhibited a remarkable UTS of 900 MPa, in contrast to the 700 MPa exhibited by the wrought material. This research clearly showcases that, despite its poor dispersion characteristics, the incorporation of rhenium can lead to a substantial increase in the strength of the material.

Silicon boron alloys have been recognized as important materials for e.g. a direct usage in ultra-high temperature latent heat thermal energy storage systems or as a batch materials for processing boron en-hanced silicide-based composites. In this work, we put new experimentally driven insights on a structure of selected Si-B binary alloys. For this reason, four Si-xB alloys (x = 2.5; 8, 13.5; 86 (at%)) were fabricated from pure elements by using a crucible-less electric arc melting technique. Nominal compositions of the alloys were selected in accordance to Si-B phase diagram as hypoeutectic, eutectic, hypereutectic and corre-sponding to the stoichiometric composition of SiB6 intermetallic phase, respectively. The fabricated Si-xB alloys were subjected to a detailed structural characterization. Additionally, a hardness, elastic moduli and fracture toughness of each phase constituent were examined through a micro-indentation technique. A co-existence of various silicon borides, namely SiB4, SiB6 and SiBn, has been experimentally documented. Obtained results allows receiving a description of each alloy in terms of microstructure, crystal structure and mechanical properties of involved phases. It was found that mechanical properties (both microhardness and Young modulus) increases with raising boron content in recognized Si-B phases. The fracture toughness of silicon borides assessed through indentation experiments was found to be in the rage of 2.13-3.29 MPa center dot m1/2. (c) 2022 Published by Elsevier B.V.

Selective laser melting (SLM) process is a promising additive manufacturing technique for the fabrication of 3D metallic components with complex geometries. When applied to a porous structure made of a low-alloyed copper, the results show a good producibility and malleability for structures made of CuNi2SiCr. On the other hand, powder metallurgy proposes spark plasma sintering (SPS) process to introduce diamond particles (resin -bonded micron-size and crystalline with 50 % coating) into a 3D-built copper structure to achieve fast and highly densified fabrication. The present work aims to achieve better positioning, consolidation and densification of the diamond particles at the desired location of the structure, which includes both the lattice and the bulk. This paper studies an additively manufactured diamond-reinforced copper structure developed for fabricating heatsinks by SLM and SPS. These metal-diamond hybrid composites can potentially be used for electro-thermal applications, refractory composites or bio/tribological applications. The demonstrated privileges include i) AM techniques using SLM with low laser power, ii) larger layer thicknesses with higher productivity and iii) rapid fabrication of porous structures with successively applying plasma sintering to fill them with hard materials like diamond particles.

This paper presents an assessment of the possibility of using digital image classifiers for tomographic images concerning ductile iron castings. The results of this work can help the development of an efficient system suggestion allowing for decision making regarding the qualitative assessment of the casting process parameters. Special attention should be focused on the fact that automatic classification in the case of ductile iron castings is difficult to perform. The biggest problem in this aspect is the high similarity of the void image, which may be a sign of a defect, and the nodular graphite image. Depending on the parameters, the tests on different photos may look similar. Presented in this article are test scenarios of the module analyzing two-dimensional tomographic images focused on the comprehensive assessment by convolutional neural network models, which are designed to classify the provided image. For the purposes of the tests, three such models were created, different from each other in terms of architecture and the number of hyperparameters and trainable parameters. The described study is a part of the decision-making system, supporting the process of qualitative analysis of the obtained cast iron castings.

A good thermochemical compatibility of ceramics intended to be applied as a vessel with the preselected phase change materials (PCMs) is crucial regarding development of novel ultra-high temperature latent heat thermal energy storage (LHTES) systems. The selection of proper refractories, that will ensure long life-time and reliable service of the system, should be preceded by the experimental verification of candidate materials upon contact heating/cooling cycles. In this chapter, we focus on the characterization of a solid/liquid interaction between Si-based PCMs and potential container materials under conditions specified by the predicted LHTES application. In this regard, new experimental procedures based on the sessile drop method were developed to examine temperature applicability limits of selected PCM/refractory couples and their thermocycling behavior upon consecutive melting/solidification cycles.

Alumina oxide coatings are widely used in many industrial applications to improve corrosion protection, wear and erosion resistances, and thermal insulation of metallic surfaces. The paper presents study of the microstructure, mechanical, and wear properties of HVOF (high velocity oxy-fuel process) sprayed of Al2O3-15 wt.% TiO2 coating with the NiAl interlayer on the surface of Al-Si alloy castings. The microstructure of Al2O3-15 wt.% TiO2/NiAl coating was characterized by light microscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDS). The analysis of the microstructure showed the formation of coating with low porosity, compact structure, good adhesion to the substrate with typical lamellar structure composed of a solid phase consisting of compounds included in the coating material and their phase variations. For analysis of the adhesion of coatings to the substrate, the scratch test was applied. An assessment of the erosive wear resistance of coatings was also carried out, confirming the significant impact of the interlayer as well as the microstructure and phase composition of the oxide coating on the wear resistance of the tested coating system. Moreover, the results were discussed in relation to the bending strength test, including cracks and delamination in the system of the Al2O3-15 wt.% TiO2/NiAl/Al-Si alloy as microhardness and erosion resistance of the coating. It was found that the introduction of the NiAl metallic interlayer significantly increased resistance to cracking and wear behavior in the studied system.

This paper presents research of the microstructure and mechanical properties of HVOF (high velocity oxy-fuel process) sprayed Cr3C2-25(Ni20Cr) coating on the surface of castings made from Al-Si alloy in the presence of NiAl transition interlayer to examine dominant microstructural factors in erosive wear of the coatings. The microstructure of ceramic coating/interlayer/metallic substrate system was characterized by light (MO) and scanning (SEM) microscopies as well as the analysis of chemical and phase composition in microareas (EDS, XRD). For analysis of quality and adhesion of coating, the scratch test was applied. The results were discussed in reference to examination of bending strength considering cracking and delamination in the system of (Cr3C2-NiCr)/NiAl/Al-Si alloy as well as hardness and erosive resistance of the coating.

In the present work Cr3C2-NiCr powder containing Al particles was deposited on ductile cast iron with high-velocity oxy-fuel (HVOF) thermal spray coating technique. An investigation was conducted to determine the role of Al particles in the Cr3C2-NiCr coating produced with HVOF technique on microstructure, mechanical and wear properties in a system Cr2C3-NiCr coating/ductile cast iron. The microstructure of the HVOF-sprayed Cr3C2-NiCr+Al coating was characterized by light microscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive X-ray spectroscopy (EDS). Microstructure analysis reveals the formation of coating with low porosity, good adhesion to the substrate and dense structure with irregularly shaped particles of Al arranged in strips and finely fragmented Cr3C2 particles embedded in a nanocrystalline Ni-Cr alloy matrix. In addition, the results were discussed in reference to examination of bending strength considering cracking and delamination in the system of (Cr3C2-NiCr+Al)/ductile cast iron as well as microhardness and wear resistance of the coating. It was found that the addition of Al particles significantly increased resistance to cracking and wear behaviour in the studied system.

Silicon-boron alloys have been recently pointed out as novel ultra-high temperature phase change materials for applications in Latent Heat Thermal Energy Storage (LHTES) and conversion systems. One of the emerging challenges related to the development of such devices is a selection of refractories applicable to build a vessel for storing molten Si-B alloys at high temperatures and under consecutive melting/solidification conditions. Previously, it has been documented that hexagonal boron nitride (h-BN) is the only one ceramic showing a non-wettability and limited reactivity with Si-B alloys at temperatures up to 1750 °C, what makes it a good candidate of the first selection for the predicted application. Nevertheless, pure h-BN shows a rather low mechanical strength that could affect a durability of the LHTES vessel. Therefore, the main purpose of this work was to examine high temperature behavior of commercial high strength h-BN composite having a nominal composition of h-BN-24ZrO 2 -6SiC (vol.%) in contact with a solid/liquid eutectic Si-3.2B alloy. Two types of sessile drop experiments were carried out: a step-contact heating up to 1750 °C, and a thermocycling at 1300 − 1450 °C composed of 15 cycles of the alloy melting/solidification. The obtained results showed a lack of wettability in the examined system at temperatures up to 1750 °C. The Si-3.2B alloy presented good repeatability of melting/solidification temperatures in consecutive thermal cycles, which was not affected by the interaction with the h-BN composite. However, due to reactions taking place between the composite’s components leading to structural degradation, it is not recommended to increase operational temperature of this material above 1450 °C.

The aim of the study was to present the possibilities of X-ray computed tomography to evaluate the internal discontinuities in multilayer ceramic moulds for precision casting critical parts of aircraft engines. Study for determination of internal discontinuities such as: porosity, micro-cracks and delamination at the ceramic moulds was carried out using the method of X-ray computed tomography. Using this method allowed to obtain a 3D virtual model of the ceramic form and, consequently, the measurement of porosity and thickness both the first layer and the constructional layer in the multilayer ceramic mould. The results are presented possibilities of computer tomography as a tool for microanalysis 3D, identify internal discontinuities and measurement of geometrical size for assessing the quality of ceramic mold in relation to the research of its technological structure.

An investigation was conducted to determine the role of Ni particles in the WC-Co coating produced with the supersonic method on microstructure, mechanical, and wear properties in a system of type: WC-Co coating/ductile cast iron. The microstructure of the thermal-sprayed WC-Co + Ni coating was characterized by scanning electron and transmission electron microscopes as well as the analysis of chemical and phase composition in microareas (EDS, XRD). The microstructure of the WC-Co + Ni coating consisted of large, partially molten Ni particles and very fine grains of WC embedded in cobalt matrix, coming to the size of nanocrystalline. Moreover, the results were discussed in reference to examination of bending strength considering cracking and delamination in the system of (WC-Co + Ni)/ductile cast iron as well as hardness and wear resistance of the coating. It was found that the addition of Ni particles was significantly increase resistance to cracking and wear behavior in the studied system.

The aim of the investigations was to compare the microstructure, mechanical, and wear properties of Cr3C2-NiCr+Ni and Cr3C2-NiCr coatings deposited by HVOF technique (the high-velocity oxygen fuel spray process) on ductile cast iron. The effect of nickel particles added to the chromium carbide coating on mechanical and wear behavior in the system of Cr 3 C 2 -NiCr+Ni/ductile cast iron was analyzed in order to improve the lifetime of coated materials. The structure with particular emphasis of characteristic of the interface in the system of composite coating (Cr 3 C 2 -NiCr+Ni)/ductile cast iron was studied using the optical, scanning, and transmission electron microscopes, as well as the analysis of chemical and phase composition in microareas. Experimental results show that HVOF-sprayed Cr3C2-NiCr+Ni composite coating exhibits low porosity, high hardness, dense structure with large, partially molten Ni particles and very fine Cr3C2 and Cr7C3 particles embedded in NiCr alloy matrix, coming to the size of nanocrystalline. The results were discussed in reference to examination of bending strength considering cracking and delamination in the system of composite coating (Cr 3 C 2 -NiCr+Ni)/ductile cast iron as well as hardness and wear resistance of the coating. The composite structure of the coating provides the relatively good plasticity of the coating, which in turn has a positive effect on the adhesion of coating to the substrate and cohesion of the composite coating (Cr3C2-NiCr+Ni) in wear conditions.

The Ag-doped Mg2Si–based materials are known for unstable thermoelectric behavior; however, the reasons are not sufficiently understood. In this work a range of experiments, analytical tools and calculations was used to unravel some questions related to the reactivity and diffusion properties of the Ag–Mg–Si system, which might contribute to the variations of thermopower. Among these, the most informative appeared quenching and diffusion experiments, calculations of phase evolution by Fact Sage and x-ray tomography of Ag-doped materials produced from powders.