Search Results (47)

This study examines the high-temperature degradation of Hastelloy C276, a corrosion-resistant nickel-based alloy, during exposure to combustion products generated by methane and 99% cracked ammonia. Using a high-pressure optical combustor (HPOC) at 4 bar and exhaust temperatures of 815–860 °C, standard tensile specimens were exposed for five hours to fully developed post-flame exhaust gases, simulating real industrial turbine or burner conditions. The surfaces and subsurface regions of the samples were analysed using scanning electron microscopy (SEM; Zeiss Sigma HD FEG-SEM, Carl Zeiss, Oberkochen, Germany) and energy-dispersive X-ray spectroscopy (EDX; Oxford Instruments X-MaxN detectors, Oxford Instruments, Abingdon, United Kingdom), while mechanical properties were evaluated by tensile testing, and the gas-phase compositions were tracked in detail for each fuel blend. Results show that exposure to methane causes moderate oxidation and some grain boundary carburisation, with localised carbon enrichment detected by high-resolution EDX mapping. In contrast, 99% cracked ammonia resulted in much more aggressive selective oxidation, as evidenced by extensive surface roughening, significant chromium depletion, and higher oxygen incorporation, correlating with increased NO_x in the exhaust gas. Tensile testing reveals that methane exposure causes severe embrittlement (yield strength +41%, elongation −53%) through grain boundary carbide precipitation, while cracked ammonia exposure results in moderate degradation (yield strength +4%, elongation −24%) with fully preserved ultimate tensile strength (870 MPa), despite more aggressive surface oxidation. These counterintuitive findings demonstrate that grain boundary integrity is more critical than surface condition for mechanical reliability. These findings underscore the importance of evaluating material compatibility in low-carbon and hydrogen/ammonia-fuelled combustion systems and establish critical microstructural benchmarks for the anticipated mechanical testing in future work. Full article

The dissimilar joining of solid-solution-strengthened superalloys and precipitation-strengthened superalloys enables complementary performance synergy, holding significant application potential in the aerospace industry. This study investigated the transient liquid phase bonding of Hastelloy X and IN738 using a BNi-2 interlayer, focusing on the effects of bonding temperature and time on interfacial microstructure evolution and mechanical properties. The results demonstrated that achieving complete isothermal solidification is paramount for joint properties, a process governed by the synergistic control of bonding temperature and time. At lower temperatures (e.g., 1050 °C), the joint centerline contained an athermal solidification zone (ASZ) rich in hard and brittle Cr-rich (∼15.9 GPa) and Ni-rich borides, which served as the failure initiation site. As the ASZ was progressively eliminated with increasing temperature, a fully isothermal solidified zone (ISZ, ∼52 μm wide) consisting of γ-Ni formed at 1100 °C. Concurrently, Cr-Mo borides (∼9.8 GPa) precipitated within the diffusion-affected zone (DAZ) on the Hastelloy X side, becoming the new potential sites for crack initiation. Prolonging the holding time at 1100 °C not only ensured complete isothermal solidification but also promoted Mo diffusion, which improved the plasticity of the Cr-Mo borides and their interfacial bonding with the γ-Ni matrix (∼5.9 GPa). This synergistic optimization resulted in a significant increase in joint shear strength, achieving a maximum value of 587 MPa under the optimal condition of 1100 °C/40 min. Full article

Hastelloy X exhibits outstanding thermal fatigue resistance, making it a promising material for repairing 50CrVA landing gear via directed energy deposition (DED). However, the substantial differences in composition and thermophysical properties between 50CrVA and Hastelloy X pose challenges by affecting interfacial microstructure and surface quality. This study investigates the effect of DED process parameters (laser power p, powder feed rate f, scanning speed v, and overlap rate) on the dilution ratio (η), microscopic morphology, surface flatness (ζ), and porosity of Hastelloy X claddings on a 50CrVA substrate. An optimization methodology integrating thermal–flow coupled simulation models and orthogonal experiments is developed to fabricate high-quality claddings. Furthermore, the corrosion–wear performance of the claddings is evaluated. The results indicate that the η of a single track increases with higher p or lower f, while it first increases and then decreases with the increase in v. Ablation marks tend to occur at excessive p or insufficient f, while low v causes surface ripples. The ζ of a single layer initially improves and subsequently deteriorates with increasing overlap rate. Porosity is significantly influenced by p and f. The optimal p, f, v, and overlap rate are 1600 W, 2.4 g/min, 240 mm/min, and 55%, respectively. The wear resistance of the cladding is nearly identical to that of the substrate, while corrosion resistance is significantly improved. This work provides a theoretical foundation for high-performance repair of 50CrVA landing gear in aircraft. Full article

This study investigates the effects of Hot Isostatic Pressing (HIP) treatment on the microstructural evolution and mechanical properties of Laser Powder Bed Fusion (LPBF)-manufactured Hastelloy H. This research evaluates the trade-offs between defect elimination, anisotropy reduction, and strength retention in well-optimized LPBF components. Specimens were manufactured using optimized LPBF parameters, achieving 99.85% density, and then subjected to HIP treatment at 1160 °C/100 MPa for 4 h. The analysis includes porosity analysis, grain size measurement, crystallographic texture evaluation, and tensile tests in two principal orientations. The results show that HIP treatment provides minimal benefits for defect elimination in already high-quality LPBF material, reducing porosity from 0.15% to <0.01%—a negligible improvement that does not translate to proportional mechanical enhancement. Tensile tests show that as-built specimens exhibited orientation-dependent strength, with XY-oriented samples reaching a yield strength (YS) of 682 MPa, ultimate tensile strength (UTS) of 864 MPa, and elongation of 17%, while XZ-oriented samples showed lower strength (YS = 621 MPa, UTS = 653 MPa) but superior ductility (elongation = 47%). After HIP treatment, anisotropy was largely removed, with both XY and XZ orientations showing comparable strength (YS ≈ 315–317 MPa, UTS ≈ 682–691 MPa) and elongation (38–41%). This indicates that HIP significantly improves ductility and isotropy at the cost of reduced strength. HIP treatment effectively eliminates the anisotropy of LPBF components, achieving uniform hardness across all orientations while reducing crystallographic texture intensity from 12.3× to 3.2× random orientation. This isotropy improvement occurs through grain-coarsening mechanisms that increase the average grain size from 7.5 μm to 13.5 μm, eliminating cellular–dendritic strengthening structures and reducing hardness by 32% (254 HV2 to 170 HV2) following Hall–Petch relationships. The conducted research confirms that HIP treatment allows for modification of the microstructure of Hastelloy X alloy, which may lead to the improvement of its mechanical properties in high-temperature applications and a significant increase in the isotropy of the material. Full article

Hastelloy is widely used in the manufacturing of high-temperature components in the aerospace industry because of its high strength and corrosion-resistant physical properties, as well as its ability to maintain excellent mechanical properties at high temperatures. However, with developments in science and technology, the amount of available components for use in high-temperature and corrosive environments is increasing, their structures are becoming more complex and varied, and requirements with regard to the surface quality of the components has also become more stringent. The integration of cold plasma (CP) and nano-lubricant minimum quantity lubrication (NMQL), within a multi-physics coupling-assisted micro-grinding process (CPNMQL), presents a promising strategy to overcome this bottleneck. In this paper, micro-grinding of Hastelloy C-276 was performed under dry, CP, NMQL, and CPNMQL conditions, respectively. Contact angle testing, X-ray photoelectron spectroscopy (XPS) analysis, and nano-scratch experiments were used to investigate the mechanism of CPNMQL and to compare the micro-milling performance under different cooling and lubrication conditions employing various characteristics such as grinding temperature, surface roughness, and 3D surface profile. The results showed that at different micro-grinding depths, the micro-grinding temperature and surface roughness were significantly reduced under CP, NMQL, and CPNMQL conditions compared to dry friction. Among them, CPNMQL showed the best performance, with 53.4% and 54.7% reductions in temperature and surface roughness, respectively, compared to the dry condition. Full article

The purpose of this study is to investigate the effects of process parameters on the microstructure and mechanical properties of the Hastelloy X (HX) alloy using a laser powder bed fusion (L-PBF) process. A combined experimental and numerical approach was used to evaluate the influence of the energy density distribution and temperature evolution on the microstructure, defects, and mechanical properties. After the specimens were built on SUS304 substrate by the L-PBF, the microstructure and defects in the specimens were analyzed by SEM and EBSD analysis methods, and then the hardness and the tensile tests were performed. The cooling rate under different laser conditions was obtained by the finite element method (FEM). The results show that a low volume energy density (VED) was applied to the unmelted powder particles, and a high energy density resulted in spherical defects. In addition, the microstructures were found to coarsen with increasing the energy density along with a tendency to strengthen the (001) texture orientation in both x–y and x–z planes. Compared to the parts with the thermal history from numerical results, the low cooling rate with high energy density had larger crystal grains elongated along the building direction, coarser sub-grains, resulting in a reduction in microhardness and yield strength together with an increase in elongation for the L-PBF HX alloy. The presented results provide new insights into the effects of parameters and the cooling rates. It can play an important role in optimizing the L-PBF processing parameters, identifying the cause of defects, and controlling the cooling rates for the crystallographic texture in such a way as to guide the development of better metrics for designing processing parameters with the desired mechanical properties. Full article

This study addresses the crack formation problem when laser cladding CoCrFeNiAl high-entropy alloy onto H13 hot-work die steel, aiming to identify suitable transition layer materials. Five nickel-based alloys—Inconel 718, Inconel 625, Hastelloy X, FGH4096, and FGH4169—are selected as alternatives. Three-point bending and hot tensile tests are conducted to assess performance under different stress directions. Test results show that the FGH4096 and FGH4169 coatings fail due to insufficient element diffusion and weak interfacial bonding. Cracks appear at the coating–substrate interface of Inconel 625 and Hastelloy X. In contrast, Inconel 718 performs best, with excellent thermal expansion matching and strong stress resistance. In the three-point bending test, the specimens with Inconel 718 transition layers did not show cracks during the loading process, while specimens with some other alloy transition layers cracked or fractured, which proves that Inconel 718 can effectively enhance the bonding force between the coating and the substrate and improve the material’s performance under bending stress. In the hot tensile test, the stress–strain curve of Inconel 718 is at a high position with a high yield strength, showing excellent resistance to plastic deformation and significantly improving the performance of the nickel-based layer under hot tensile conditions. Therefore, Inconel 718 is identified as the optimal transition layer material. Full article

Hybrid layered reinforced materials are able to increase the reliability, durability, and expand the functionality of high-temperature components in supercritical and ultra-supercritical power plants and in oil, gas, and petrochemical equipment operating under conditions with multifactorial influences (temperature, force, deformation). As a result of this research, surface reinforced ceramic composite materials with a gradient distribution of properties have been developed. These materials include thermal barrier layers (Gd₂O₃-Yb₂O₃-Y₂O₃-ZrO₂) and Ni-based layers reinforced with ceramic carbide and oxide particles. They are strong, have a high heat and wear resistance, and provide the specified functional and mechanical properties. The formation technology for the hybrid composites has also been developed. This technology includes the mechanical alloying of powder compositions, which is followed by vacuum plasma spraying. The structure of the powder compositions and composite layers, the density of the obtained composite materials, and the heat and wear resistance of the composites have also been investigated. The microhardness of the alloy layers of the hybrid composite materials Hastelloy X–GYYZO–material 1 and Hastelloy X–GYYZO–material 2 was as follows: super alloy Hastelloy X, HV_0.2 = 3.8–3.95 GPa; layer GYYZO, HV_0.3 = 16.1–16.7 GPa; layer material 1, HV_0.3 =18.3–18.8 GPa; layer material 2, HV_0.3 =19.1–19.6 GPa. The influence of the refractory phase of HfC and TaC on the strength of the composites was studied. It was found that the maximum strength (710–715 MPa) in the composites Hastelloy X—GYYZO—material 1 and Hastelloy X–GYYZO–material 2 is achieved with a content of HfC and TaC–27–28%. Full article

Composite coatings reinforced with varying mass fractions of SiC particles were successfully fabricated on 316 stainless steel substrates via laser cladding. The phase compositions, elemental distribution, microstructural characteristics, hardness, wear resistance and corrosion resistance of the composite coatings were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Vickers hardness testing, friction-wear testing and electrochemical methods. The coatings have no obvious pores, cracks or other defects. The phase compositions of the Hastelloy C276 coating includes γ-(Ni, Fe), Ni₂C, M₆C, M₂(C, N) and M₂₃C₆. SiC addition resulted in the formation of high-hardness phases, such as Cr₃Si and S₅C₃, with their peak intensity increasing with SiC content. The dendrites extend from the bonding zone towards the top of the coatings, and the crystal direction diffuses from the bottom to each area. Compared with the dendritic crystals formed at the bottom, the microstructure at the top is mostly equiaxed crystals and cellular crystals with smaller volume. When SiC powder particles are present around the crystals, the microstructure of the cladding layer grows acicular crystals containing Si and C. These acicular crystals tend to extend away from the residual SiC powder particles, and the grain size in this region is smaller and more densely distributed. This indicates that both melted and unmelted SiC powder particles can contribute to refining the grain structure of the cladding layer. The optimal SiC addition was determined to be 9 wt%, yielding an average microhardness of 670.1 HV_0.5, which is 3.05 times that of the substrate and 1.19 times that of the 0 wt% SiC coating. The wear resistance was significantly enhanced, reflected by a friction coefficient of 0.17 (43.59% of the substrate, 68% of 0 wt%) and a wear rate of 14.32 × 10⁻⁶ mm³N⁻¹·m⁻¹ (27.35% of the substrate, 40.74% of 0 wt%). The self-corrosion potential measured at 315 mV, with a self-corrosion current density of 6.884 × 10⁻⁶ A/cm², and the electrochemical charge-transfer resistance was approximately 25 times that of the substrate and 1.26 times that of the 0 wt%. In this work, SiC-reinforced Hastelloy-SiC composite coating was studied, which provides a new solution to improve the hardness, wear resistance and corrosion resistance of 316L stainless steel. Full article

Additive manufacturing (AM) methods like powder bed fusion–laser beam (PBF-LB) enable complex geometry production. However, understanding and predicting the microstructural properties of AM parts remain challenging due to the inherent non-homogeneity introduced during the manufacturing process. This study demonstrates a novel approach for 3D microstructure representation and virtual testing of non-homogeneous AM materials using 2d electron backscatter diffraction (EBSD) data. By employing the representative volume element (RVE) method, we reconstruct the 3D microstructure from 2D EBSD datasets, effectively capturing the grain morphological characteristics of PBF-LB-produced Hastelloy X. Using validated RVE data, we artificially generate combinations of two grain textures to gain deeper insight into locally affected areas, particularly the stress distribution within the interfaces, as well as global material behavior, exploring non-homogeneity. Computational homogenization (CH) utilizing a crystal elasticity finite element (CEFE) method is used to virtually test and predict directional elastic properties, offering insights into relationships between microstructure evolution and property correlation. The experimentally validated results show a strong correlation, with only 0.5–3.5% correlation error for the selected grain tessellation method. This consistency and reliability of the methodology provide high confidence for additional virtual tests predicting the properties of non-homogeneous, artificially generated combined-grain structures. Full article

The results of experimental and numerical studies of plastic forming of sheets made of the difficult-to-deform Hastelloy X, a nickel-based alloy with a thickness of 1 mm, using layered elastomeric punches and steel dies, are presented in this publication. The elastomeric punches were characterized by hardness in the range of 50–90 Shore A, while the dies were made of 90MnCrV8 steel with a hardness of over 60 HRC. The principle of operating the stamping die was based on the Guerin method. The finite-element-based numerical modeling of the forming process for various configurations of polyurethane inserts was also carried out. The results obtained from numerical modeling were confirmed by the results of experimental tests. The drawpieces obtained through sheet forming were subjected to geometry tests using optical 3D scanning. The results confirmed that in the case of forming difficult-to-deform Hastelloy X, Ni-based alloy sheets, the hardness of the polyurethane inserts significantly affected the geometric quality of the obtained drawpieces. Significant nonuniform sheet metal deformations were also found, which may pose a problem in the process of designing forming tools and the technology of the plastic forming of Hastelloy X, Ni-based alloy sheets. Full article

This review sets out to investigate the detrimental impacts of hydrogen gas (H₂) on critical boiler components and provide appropriate state-of-the-art mitigation measures and future research directions to advance its use in industrial boiler operations. Specifically, the study focused on hydrogen embrittlement (HE) and high-temperature hydrogen attack (HTHA) and their effects on boiler components. The study provided a fundamental understanding of the evolution of these damage mechanisms in materials and their potential impact on critical boiler components in different operational contexts. Subsequently, the review highlighted general and specific mitigation measures, hydrogen-compatible materials (such as single-crystal PWA 1480E, Inconel 625, and Hastelloy X), and hydrogen barrier coatings (such as TiAlN) for mitigating potential hydrogen-induced damages in critical boiler components. This study also identified strategic material selection approaches and advanced approaches based on computational modeling (such as phase-field modeling) and data-driven machine learning models that could be leveraged to mitigate potential equipment failures due to HE and HTHA under elevated H₂ conditions. Finally, future research directions were outlined to facilitate future implementation of mitigation measures, material selection studies, and advanced approaches to promote the extensive and sustainable use of H₂ in industrial boiler operations. Full article

The application potential of additive manufacturing nickel-based superalloys in aeroengines and gas turbines is extensive, and evaluating their mechanical properties is crucial for promoting the engineering application in load-bearing components. In this study, Hastelloy X alloy was prepared using the laser powder bed fusion process combined with solution heat treatment. The tensile and high cycle fatigue properties were experimentally investigated at room temperature as well as two typical elevated temperatures, 650 °C and 815 °C. It was found that, during elevated-temperature tensile deformation, the alloy exhibits significant serrated flow behavior, primarily observed during the initial stage of plastic deformation at 650 °C but occurring throughout the entire plastic deformation process at 815 °C. Notably, when deformation is small, sawtooth fluctuations are significantly higher at 815 °C compared to 650 °C. Irregular subsurface lack of fusion defects serve as primary sources for fatigue crack initiation in this alloy including both single-source and multi-source initiation mechanisms; moreover, oxidation on fracture surfaces is more prone to occur at elevated temperatures, particularly at 815 °C. Full article

The phase, mechanical properties, corrosion resistance, hydrophobicity, and interfacial contact resistance of Hastelloy X were investigated to evaluate its performance in proton exchange membrane fuel cells (PEMFCs). For comparison, the corresponding performance of 304 stainless steel (304SS) was also tested. Hastelloy X exhibited a single-phase face-centered cubic structure with a yield strength of 445.5 MPa and a hardness of 262.7 HV. Both Hastelloy X and 304SS exhibited poor hydrophobicity because the water contact angles were all below 80°. In a simulated PEMFC working environment (0.5 M H₂SO₄ + 2 ppm HF, 80 °C, H₂), Hastelloy X exhibited better corrosion resistance than 304SS. At 140 N·cm⁻², the interfacial contact resistance of Hastelloy X can reach as low as 7.4 mΩ·cm². Considering its overall performance, Hastelloy X has better potential application than 304SS as bipolar plate material in PEMFCs. Full article

H₂ production via membrane-assisted steam methane reforming (MA-SMR) can ensure higher energy efficiency and lower emissions compared to conventional reforming processes (SMR). Ceramic-supported Pd–Ag membranes have been extensively investigated for membrane-assisted steam methane reforming applications, with outstanding performance. However, costs, sealings for integration in the reactor structure, and resistance to solicitations remain challenging issues. In this work, the surface quality of a low-cost, porous Hastelloy-X filter is improved by asymmetric filling with α-Al₂O₃ of decreasing size and deposition of γ-Al₂O₃ as an interdiffusion barrier. On the modified support, a thin Pd–Ag layer was deposited via electroless plating (ELP), resulting in a membrane with H₂/N₂ selectivity >10,000. The permeation characteristics of the membrane were studied, followed by testing for membrane-assisted methane steam reforming. The results showed the ability of the membrane reactor to overcome thermodynamic conversion of the conventional process for all explored operating conditions, as well as ensuring 99.3% H₂ purity in the permeate stream at 500 °C and 4 bar. Full article