Search Results (36)

This work investigates the effect of the addition of tungsten carbide (WC) particles as reinforcements to Ni (Inconel 625) versus Co (Stellite 6) alloys during deposition by laser cladding to form wear-resistant metal matrix composite (MMC) coatings. While the related literature often associates the presence of WC with the enhanced wear performance of MMC coatings, this work shows that such an effect is not universal as it may critically depend on the metallic matrix employed. Thus, to demonstrate whether the reinforcement and matrix act synergically in such a scenario or not, MMC coatings formed by Inconel 625 and Stellite 6, both with WC content ranging from 10% to 40%, were deposited under the same laser cladding setup on AISI 304 stainless steel substrates, being WC-free samples produced together for comparison basis. As expected, the hardness levels increased with more WC presence in both matrices, but the wear resistance was specifically evaluated by means of the metal wheel abrasion test (ASTM B611). The results revealed that the use of WC as a reinforcement indeed affects the matrix materials differently; for Stellite 6, the wear resistance increased with up to 20% of WC (in contrast to the hardness indication), whereas for Inconel 625, the wear resistance progressively decreased with more WC content. It was observed via scanning electron microscopy (SEM) that the WC particles within the Inconel 625 alloy tended to intensive cracking, being in this way more prone to detach from the matrix and hence representing a weakening factor for the effectiveness of the coatings produced. Thus, it is concluded that the addition of WC particles, as potential reinforcements for MMC coatings, is not always effective (synergic with the matrix) in providing wear resistance, hence, opposing the prevailing consensus. This outcome and its reasons will certainly help with insights into proper design of MMC coatings, starting with the importance of matrix material selection. 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

In this study, Inconel 625 coatings were deposited onto the surface of 2Cr13 stainless steel via laser cladding technology to ensure their corrosion resistance and mechanical properties. The microstructure and characteristics of coatings were adjusted by varying laser power (1200, 1500, and 1800 W), scanning speed (10, 15, and 25 mm/s), and overlap rate (40%, 50%, and 70%). The results showed that the impact resistance of blades was improved by 23% to 30% compared to the substrate, whereas the self-corrosion current density was reduced by 94%–98%, which indicated the outstanding resistance of specimens to damage and corrosion. At the same time, the appropriate processing parameters enabled the surface hardness of the 2Cr13 substrate to be improved. This study provides practical technical guidance for the repair of 2Cr13 blades and a comprehensive enhancement of their corrosion resistance and mechanical properties through parameter optimization. Full article

High-temperature corrosion within waste incineration boilers leads to the thinning of their four-tube heating surfaces and frequent tube ruptures, posing a formidable challenge to the development of the waste-to-energy sector. This predicament critically constrains the advancement of China’s waste management and environmental protection sectors. This study focuses on elucidating high-temperature corrosion mechanisms and exploring coating protection methodologies relevant to waste boilers. For corrosion mechanisms, the study comprehensively reviews various factors such as the characteristics of high-temperature chlorine-induced corrosion, gaseous- and molten-chloride-induced corrosion, and sulfidation and multiphase-coupled corrosion; the influence of wall temperature on corrosion; and temperature effects on corrosion. Regarding coating protection technologies, this study traces the historical progression of various coating techniques, providing an overview of methods such as supersonic flame spraying, Inconel 625 surfacing, laser cladding, induction melting, thermosetting-reaction nanoceramic coating, and aluminizing. Special emphasis is placed on the mechanisms and principles of the widely adopted surfacing and induction melting techniques. Overall, the study ventures into the prevailing challenges and envisions the future trajectories of high-temperature anticorrosion mechanisms and coating protection technologies for China’s waste boiler sector. Full article

The deposition of agglomerated hydroxyapatite (HAp) powders by low-pressure cold spray has been a topic of interest in recent years. Key parameters influencing the deposition of HAp powders include particle morphology and impact kinetic energy. This work examines the deposition of HAp powders on various metal surfaces to assess the impact of substrate properties on the formation of HAp deposits via cold spray. The substrates studied here encompass metals with varying hardness and thermal conductivities, including Al6061, Inconel alloy 625, AISI 316 stainless steel, H13 tool steel, Ti6Al4V, and AZ31 alloy. Single-track experiments offer insights into the initial interactions between HAp particles and different substrate surfaces. In this study, the results indicate that the ductility of the substrate may enhance HAp particle deposition only at the first deposition stages where substrate/particle interaction is the most critical factor for deposition. Features on the substrate associated with the first deposition sprayed layer include localized substrate deformation and the formation of clusters of HAp agglomerates, which aid in HAp deposition. Furthermore, after multiple spraying passes on the various metallic surfaces, deposition efficiency was significantly reduced when the build-up process of HAp coatings shifted from ceramic/metal to ceramic/ceramic interactions. Overall, this study achieved agglomerated HAp deposits with high deposition efficiencies (30–60%) through single-track experiments and resulted in the preparation of HAp coatings on various substrates with thickness values ranging from 24 to 53 µm. These coatings exhibited bioactive behavior in simulated body fluid. Full article

Water-cooled wall tubes are susceptible to high-temperature corrosion during service. Applying high-performance coatings via laser cladding on the tube surfaces can significantly enhance corrosion resistance and extend the service life of the tubes, providing substantial economic advantages. This paper prepared Y₂O₃/IN625 composite coating by means of high-speed laser cladding. Furthermore, the effects of Y₂O₃ addition on the microstructure evolution, hardness, as well as the high-temperature corrosion behaviors have been systematically investigated. The results show that Y₂O₃ addition can effectively refine the microstructure of the Inconel 625 coating, but the phase composition has little change. The coating’s hardness can also be improved by about 7.7%, reaching about 300 HV. Compared to Inconel 625 coating, the Y₂O₃-added composited coating shows superior high-temperature corrosion resistance, with the corrosion mass gain decreased by about 36.6%. The denser and tightly bonded Cr-rich oxides layer can be formed adjacent to the coating surface, which plays a predominant role in improving the coating corrosion resistance. 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

Good-quality metallurgical bonding and a high degree of automation are critical for using laser cladding technology in on-site repairs. At present, most of the on-site repairs are carried out manually, which can bring about problems such as complicated operation procedures, uneven repair quality, and personnel injuries. In this study, a surface repair method that combined laser cleaning with cladding (LCC) was proposed. First, the plates were scanned with a high-frequency pulsed laser to remove the surface impurity layer. The surface was then coated with Inconel 625 powder while irradiated with a continuous laser for the cladding. Both the macro-morphology and microstructure of the surface were examined, and mechanical property tests were also conducted. The metallographic and scanning electron microscope images indicated that, compared to the manual polishing and laser cladding process, the LCC specimens had a better metallurgical bonding quality and a thicker clad layer. The average hardness of the clad layer on the LCC specimens was high at 256.47 HV, 36.2% higher than that of the Q345R substrate. Compared to the Q345R specimens of the same size, the LCC specimens showed an increased impact on the energy absorption, yield strength, and tensile strength. This study provides a new approach for improving the automation and cladding quality of on-site repairs. Full article

Friction, wear, and corrosion of engineering components operating in harsh environments can be substantially improved by applying hard, corrosion-resistant coatings to prolong their useful lives. Nickel superalloys are particularly relevant due to their excellent mechanical properties and corrosion resistance at elevated temperatures. Among the various coating techniques, arc welding processes are suitable due to their good deposition rate and reliability. This work aimed to evaluate the effect of the shielding gas and after-deposition heat treatment on the microstructure and mechanical properties of Inconel 625 coatings deposited by the GMAW process. The coatings were deposited onto carbon steel plates using two mixtures of shielding gases (Ar+25%CO₂ and Ar+25%He) without interpass temperature control. The specimens were analyzed both as welded and after heat treatment (heating for 1 h at 1000 °C and air cooling) using Vickers hardness tests, scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDS), and wavelength dispersion spectrometry (WDS). The coatings that used Ar+25%He-shielding gas were harder and showed more precipitate formation, which was associated with the higher cooling rates involved. As for the heat treatment, it led to a reduction in the segregation of the alloying elements in the interdendritic region via diffusion and a reduction in surface hardness. Full article

The presented research determined the performance of the protective coatings against the corrosion process under biomass and refuse-derived fuel (RDF) ash deposits. High-temperature corrosion tests were performed on steel grades intended for use in the fabrication of pressure parts working in elevated temperatures such as superheaters in power boilers. Two steel grades were investigated, P235GH and 16Mo3, and two protective coatings were applied, Inconel 625 and Alloy 310. The samples were sourced from the industrial boiler manufacturing company. The samples were exposed to two ashes originating from biofuels and one ash originating from RDF for comparison, all collected from Polish heat plants and power plants. Exposures were carried out in an oxidizing atmosphere for a maximum time of 504 h. The test temperatures of 480, 520, and 580 °C simulated superheater conditions of biofuel- and waste-fired power boilers. The corrosion kinetics were determined by weight change measurements conducted after 24, 168, and 504 h of the exposure. Regardless of the exposure temperature and the type of ash under which the samples were investigated, the use of 2.0 mm thick protective coatings resulted in smaller increases in the weight of the tested coupons which proves that alloy coatings give measurable results and are good remedies for chlorine-induced corrosion. Full article

This study investigates the microstructure and tribological behavior of Inconel 625 overlays applied via GMAW (Gas Metal Arc Welding) with and without a 316LSi stainless-steel intermediate layer on top of A36 steel. The microstructural characterization was conducted via FESEM with EDS. The tribological behavior was evaluated using a tribometer in a reciprocating configuration. The results showed that the wear rate of the Inconel 625 weld overlay with the 316LSi intermediate layer was higher than without it. However, no variations were observed in terms of hardness and the friction coefficient of the Inconel 625 weld overlays. The difference in the behavior of the two coatings was justified due to the microstructure morphology found in each case and chemical composition. When applied without the intermediate layer, Inconel 625 coating’s structure was dendritic, whereas it was cellular otherwise. An increase in the amount of Nb was observed in the layer deposited over 316LSi. This rise likely led to an increase in the number of precipitates and/or Laves phase formation. Thus, the results indicated that the difference in thermal conductivity and dilution between the stainless and carbon steels modifies the morphology of the microstructure of the Inconel 625 weld overlay, decreasing wear resistance when deposited on top of the stainless steel. Full article

Zirconates of rare earth elements have emerged as promising candidates for thermal barrier coatings (TBC). This study investigates the hot corrosion resistance of single-layered ceramic coatings composed of Gd₂Zr₂O₇, Sm₂Zr₂O₇, and Nd₂Zr₂O₇. The coatings were prepared using air plasma spraying and applied to an Inconel [IN] 625 substrate. Experimental assessments were conducted to examine the hot corrosion behaviour by subjecting the coatings to pure magnesium sulfate (MgSO₄) salt at 1000 °C for 24 h and a 50/50 mole percent Na₂SO₄ and MgSO₄ mixture at 900 °C for cyclic durations of 5, 10, 15, and 20 h. This combination of salts creates a highly corrosive environment. This short test was carried out due to the necessity of the initial stages of the destruction process characterization. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersion spectroscopy (EDS) techniques were utilized to identify and analyse the reaction products. At 1000 °C, no chemical reaction products were observed between MgSO₄ and Gd₂Zr₂O₇, Sm₂Zr₂O₇, and Nd₂Zr₂O₇. However, in the presence of the MgSO₄ + Na₂SO₄ mixture, the zirconate coatings reacted, resulting in the formation of reaction products such as Gd(SO₄)₃, Gd₂O₂SO₄, Gd₂O₃, Sm₂O₂SO₄, Sm₂(SO₄)₃, Sm₂O₃, MgO, Nd₂(SO₄)₃, Na₂O, and m-ZrO₂. These compounds are formed due to the interaction of rare earth oxides with a low-temperature-melting eutectic Na₂SO₄+ (3MgSO₄ × Na₂SO₄) melted at 666 °C. Despite the aggressive nature of the corrosive environment, the decomposition of rare earth zirconates was relatively limited, indicating satisfactory resistance to hot corrosion. Among the zirconate systems studied, Gd₂Zr₂O₇ exhibited the lowest resistance to the MgSO₄ + Na₂SO₄-based corrosive environment, while Sm₂Zr₂O₇ and Nd₂Zr₂O₇ demonstrated better corrosion resistance. Full article

The presented work deals with the investigation of mechanical tribological properties on Inconel 625 superalloy, which is welded on a 16Mo3 steel pipe. The wall thickness of the basic steel pipe was 7 mm, while the average thickness of the welded layer was 3.5 mm. The coating was made by the cold metal transfer (CMT) method. A supercritical bending of 180° was performed on the material welded in this way while cold. The mechanical properties evaluated were hardness, wear resistance, coefficient of friction (COF) and change in surface roughness for both materials. The UMT Tribolab laboratory equipment was used to measure COF and wear resistance by the Ball-on-flat method, which used a G40 steel pressure ball. The entire process took place at an elevated temperature of 500 °C. The measured results show that the materials after bending are reinforced by plastic deformation, which leads to an increase in hardness and also resistance to wear. Superalloy Inconel 625 shows approximately seven times higher rate of wear compared to steel 16Mo3 due to the creation of local oxidation areas that support the formation of abrasive wear and do not create a solid lubricant, as in the case of steel 16Mo3. Strain hardening leads to a reduction of possible wear on Inconel 625 superalloy as well as on 16Mo3 steel. In the case of the friction process, the places of supercritical bending of the structure showed the greatest resistance to wear compared to the non-deformed structure. Full article

Laser material deposition (LMD) is a widely used coating process in industry. However, to increase its economic appeal, higher process speeds are required. The solution to this challenge is an innovative modification known as extreme high-speed laser material deposition (EHLA). EHLA allows for an impressive increase in process speed from 2 m/min for conventional LMD to 500 m/min. With the ability to adjust process parameters, EHLA can generate tailor-made surface properties, expanding its potential application beyond current industrial uses. In this novel study, we explore the effects of relative positioning between tools (laser beam and powder–gas jet) and substrate on the surface properties of EHLA coatings. By laterally and axially offsetting the tools, the proportional energy coupling of the laser radiation into the powder–gas jet and substrate can be modified. Altering the position of the powder–gas jet can also affect the weld pool flow or number of particle attachments, thereby affecting surface properties. This approach allows for the adjustment of surface roughness over a wide range—from smooth, quasi-laser-polished surfaces to rough surfaces covered with particle adhesions. Full article

Nickel-based superalloys, namely INCONEL^® variants, have had an increase in applications throughout various industries like aeronautics, automotive and energy power plants. These superalloys can withstand high-temperature applications without suffering from creep, making them extremely appealing and suitable for manufactured goods such as jet engines or steam turbines. Nevertheless, INCONEL^® alloys are considered difficult-to-cut materials, not only due to their superior material properties but also because of their poor thermal conductivity (k) and severe work hardening, which may lead to premature tool wear (TW) and poor final product finishing. In this regard, it is of paramount importance to optimise the machining parameters, to strengthen the process performance outcomes concerning the quality and cost of the product. The present review aims to systematically summarize and analyse the progress taken within the field of INCONEL^® machining sensitively over the past five years, with some exceptions, and present the most recent solutions found in the industry, as well as the prospects from researchers. To accomplish this article, ScienceDirect, Springer, Taylor & Francis, Wiley and ASME have been used as sources of information as a result of great fidelity knowledge. Books from Woodhead Publishing Series, CRC Press and Academic Press have been also used. The main keywords used in searching information were: “Nickel-based superalloys”, “INCONEL^® 718”, “INCONEL^® 625” “INCONEL^® Machining processes” and “Tool-wear mechanisms”. The combined use of these keywords was crucial to filter the huge information currently available about the evolution of INCONEL^® machining technologies. As a main contribution to this work, three SWOT analyses are provided on information that is dispersed in several articles. It was found that significant progress in the traditional cutting tool technologies has been made, nonetheless, the machining of INCONEL^® 718 and 625 is still considered a great challenge due to the intrinsic characteristics of those Ni-based-superalloys, whose machining promotes high-wear to the tools and coatings used. Full article