Examinando por Autor "Poza, Pedro"

Mostrando 1 - 12 de 12

A study of the parameters affecting the particle velocity in cold-spray: Theoretical results and comparison with experimental data
(Elsevier, 2023) Alonso, Luis; Garrido Maneiro, Miguel Ángel; Poza, Pedro
Within coating applications, cold-spray is nowadays an extended technique commonly used in environments such as the additive manufacturing or repair industries. The differential factor that leads this approach to be chosen over others is its low deposition temperature. The need for ensuring the resistance and durability of the free-standing components has led to the development of models that can predict the kinetic energy of the particles, which is the main driving parameter affecting the deposit performance. In this study, an optimisation theoretical model, previously developed by the authors, is validated with the experimental exit particle velocity data taken from commercial geometries and using Fluent simulations available in literature. The aim of this work is to relate fundamental parameters in the cold-spray process such as the stagnation conditions, nozzle geometry, powder size or particle velocity. This objective is achieved by creating novel interdependent maps connecting these pivotal data by virtue of the model presented. Several graphs describing the final particle velocity depending on the stagnation pressure and temperature are obtained along with the optimal geometry for a wide range of materials (aluminium, titanium, steel, Inconel 625 and copper). In addition, the analytical model is able to hand over a deposition window of particle sizes and velocities that can be achieved using a specific cold-spray equipment. Both set of maps combined together can be a powerful tool which users and manufacturers can benefit from on the grounds that they do not only provide information about whether a deposition can be achieved or not with a cold-spray equipment but also about the stagnation conditions needed. The results obtained with this methodology reflect the limitations of low and medium-pressure equipment in terms of the maximum particle diameter that can be deposited and constitute a novel advance in the state of art of cold-spray. Moreover, the fundamental parameter regarding the geometry, namely the ratio between the nozzle exit and the nozzle throat diameters, is represented as a function of the above-mentioned parameters.
Alternative low-power plasma-sprayed inconel 625 coatings for thermal solar receivers: Effects of high temperature exposure on adhesion and solar absorptivity
(Elsevier, 2022) Merino-Millan, David; Múnez, Claudio J.; Garrido-Maneiro, Miguel Ángel; Poza, Pedro
Over recent years, renewable energy technologies have focused on increasing performance and efficiency, and on the reduction of maintenance costs. In this work, thermal-sprayed Inconel 625 coatings have been studied as an alternative for concentrated solar power plants receivers. A low-power compact plasma spray system was used to deposit coatings onto two substrates: grade 22 ferritic steel and AISI 316 L austenitic steel. This system may be used for in-situ maintenance or repair purposes. The coatings were heat-treated at two temperatures: 520 ◦C and 800 ◦C, at different exposure times. The aim of this work was to evaluate the effect of this treatment on the adherence and solar absorptivity of the Inconel 625 coatings. The results showed that, at higher temperatures and longer exposure times, better adherence and absorptivity are achieved. Adherence values above 60 MPa were obtained due to diffusion in the coating-substrate interface. Additionally, absorptivity values above 93% were measured due to oxide formation on the coating surface during heat treatment. Furthermore, the highest temperature of the oxidized treatment reported the highest values of absorptivity. These results show that the developed Inconel 625 coatings could be considered as a possible alternative to improve the performance of concentrated solar power plants.
An optimisation method for the cold-spray process: On the nozzle geometry
(Elsevier Ltd., 2022-01-08) Alonso, Luis; Garrido, Miguel Ángel; Poza, Pedro
Actualmente, el proceso de proyección en frío es una técnica muy utilizada en aplicaciones de deposición de recubrimientos. La baja temperatura del proceso de deposición es la característica distintiva que lo hace adecuado para muchas actividades de fabricación aditiva, como la reparación y restauración de componentes dañados. La fiabilidad de los recubrimientos depende en gran medida de la velocidad del polvo durante su impacto sobre la superficie objetivo. Las condiciones de proyección, como la presión y la temperatura del gas portador y la geometría de la boquilla, controlan la aceleración de las partículas de polvo. En consecuencia, existe un interés creciente en la optimización de la geometría de la boquilla para maximizar la aceleración de las partículas a través de la trayectoria que siguen a lo largo de dicha boquilla. En contraste con varios enfoques existentes para lograr este objetivo (modelado de elementos finitos, enfoque experimental y métodos analíticos), en este estudio se desarrolló un modelo alternativo basado en la teoría isoentrópica unidimensional que explica la dinámica del flujo diluido de dos fases. En primer lugar, se llevó a cabo un análisis de las hipótesis habituales utilizadas para obtener la ecuación de movimiento de la partícula. Posteriormente, con los nuevos conocimientos obtenidos en el análisis anterior, se realizó un nuevo modelo teórico para la optimización de la parte divergente de la boquilla, considerando una restricción de ángulo geométrico. Este modelo se basa en la integración numérica de la ecuación de movimiento de la partícula, asegurando la maximización de la fuerza de arrastre de la partícula mediante el método del multiplicador de Lagrange. Una vez formulado el modelo analítico, se obtiene un conjunto de curvas que describen los parámetros geométricos óptimos para diferentes condiciones. Además, se presentan algunas geometrías óptimas que demuestran la baja influencia de la restricción del ángulo. Además, se muestra la relación inversamente proporcional entre la presión de proyección y la temperatura.
Cold-sprayed coatings: Microstructure, mechanical properties, and wear behaviour
(Elsevier, 2021) Poza, Pedro; Garrido-Maneiro, Miguel Ángel
Deposition of coatings on the surface of a bulk material is a versatile, economical, and effective strategy to provide additional features to the bulk material, mainly to improve its functionality and extend its service life. Among all the thermal deposition techniques, cold spray (CS) is the only technique in which particles are deposited below their melting point, and therefore, it is a solid-state processing technique. Coatings generated via CS exhibit different characteristics from those of the coatings produced by other methods; this may make CS a competitive technique for the repair and even for the manufacture of self-standing components. This study presents a basic description of CS and a review of its applications in the deposition of metallic coatings, specifically those based on materials such as Al- and Ti-based alloys, used in aeronautical components. CS is a thermal spray technique that enables the production of coatings with properties and behaviours similar to those of bulk materials with similar compositions.
Erosion behaviour of cold sprayed stainless-steel coatings for civil infrastructures: An energetic approach
(Elsevier, 2024-06) Cortés, Rocío; Garrido-Maneiro, Miguel Ángel; Poza, Pedro
Along with corrosion, erosion is one of the main causes of damage to civil infrastructures. The continuous impact of fine particles carried by the air produces a deterioration in the elements of these structures. When this damage is significant, these elements are replaced by new ones. In this work, the possibility of extending the useful life of these components by spraying coatings on the damaged areas is proposed. In this sense, repair techniques such as cold spray deposition are possibilities for this purpose. Therefore, this study focuses on evaluating the erosion behaviour of stainless-steel coatings deposited on structural steel. In addition, the erosion results have been correlated with the model proposed by Hutchings, and an energetic interpretation of the erosion process through this model has been proposed. To carry out this study, stainless steel coatings have been deposited on carbon steel substrates to improve their resistance to corrosion. Different spraying temperatures, from 800 °C to 1100 °C, combined with different pressures of the carrier gas, from 40 to 70 bar, have been analysed. The elastic moduli of the coatings, and their stress-strain curve, have been determined by depth sensing indentation tests with Berkovich and spherical tips, respectively. Erosion tests with normal incidence have been programmed to obtain the corresponding erosion rates. From the results of this work, the optimal projection conditions of stainless steel on carbon steel substrates for the repair of civil infrastructures subjected to erosion processes could be identified
Evaluating the effect of deposition conditions on the local wear resistance of cold sprayed stainless steel coatings
(Elsevier, 2023) Cortés, Rocío; Garrido-Maneiro, Miguel Ángel; Poza, Pedro
The useful service life of metallic structures is affected by the exposure to the meteorological phenomena. In this sense, the continuous impact of particles suspended in the atmosphere could produce microscratches on the surfaces of these components, generating several wear degradations. These damaged surfaces can be repaired in order to increase their service life, avoiding component replacement and reducing the environmental impact. Recently, coatings deposition by cold spray has been revealed as a promising strategy for repairing damaged components. Therefore, the main objective of this work is focused on the analysis of wear resistance against micro-scratching in metallic coatings. For this purpose, 316L stainless steel powders were deposited onto low carbon steel S355J2 by cold spray, varying the pressure and temperature of the propellant gas. Nanoindentation tests were carried out to determine hardness and elastic modulus. The wear rates and the friction coefficients were measured through microscratch tests using a Berkovich tip. The wear mechanisms were analysed evaluating the scratch grooves in the scanning electron microscope. Finally, the relationship between hardness and wear rate was determined.
Hardness and Young's modulus evolution of low-power plasma sprayed Inconel 625 coatings exposed to high temperatures
(Elsevier, 2024-10-30) Merino-Millán, David; Garrido-Maneiro, Miguel Ángel; Múnez, Claudio J.; Poza, Pedro
The use of renewable energy sources has been increasing in recent years as it aims to balance the production of fossil fuels by 2050. Among the various alternatives, concentrated solar power plants are considered the most feasible due to their capability of storing energy. Ongoing research is conducted to enhance the performance of third-generation plants by achieving higher temperatures. It makes necessary to explore new materials. This research is focused on concentrated solar power plants with central tower receivers, for which coatings used nowadays do not withstand the new requirements. For this reason, an alternative plasma sprayed Inconel 625 coating has been proposed. This study confidently presents an analysis of the high temperature exposure effects on the coating's mechanical properties at two temperatures, 520 and 800 °C. The study focuses on the Young's modulus and hardness, and the results demonstrate a significant improvement in these properties due to the formation of secondary phases. Coating hardness increased gradually from 4.12 GPa to 5.3 GPa during exposition at 520 °C. In contrast, the increment was attained quickly during the first 24 h exposure at 800 °C, reaching 4.5 GPa, and then maintained for all times studied. The microstructure was characterized using transmission electron microscopy, which identified the presence of carbides and intermetallic phases. The application of these coatings will significantly enhance the performance of solar receivers due to their superior properties compared to the currently available Pyromark coatings
Improving cold sprayed Ti-6Al-4V coatings controlling processing parameters: Effect on microstructure and scratch behaviour
(Elsevier, 2023) Sirvent, Paloma; Garrido-Maneiro, Miguel Ángel; Poza, Pedro
In this work, the local wear properties of cold-sprayed (CS) Ti-6Al-4V coatings were studied to evaluate their application for aeronautical components repair. Two different CS conditions were used, and one condition was also heat-treated. A thorough microstructural study was first done to correlate the microstructure with the wear properties. Then, microscratch tests were performed. The wear rates were calculated analytically, and this method was validated with confocal microscopy. Similar wear rates to that of the material to be repaired (substrate) were obtained for the CS coating sprayed at higher temperatures and for the heat-treated one. The wear resistance was related to the ability of the coating to plastically deform and thus, with the arrangements of different dislocations observed in the coatings.
Local wear resistance of Inconel 625 coatings processed by different thermal techniques: A comparative study
(Elsevier, 2023) Cortés, Rocío; Garrido-Maneiro, Miguel Ángel; Koivuluoto, Heli; Bolelli, Giovanni; Morelli, Stefania; Testa, Veronica; Lusvarghi, Luca; Kondas, Jan; Poza, Pedro
Ni-base superalloys, like Inconel 625, are extensively used in several applications due to their good performance at high temperature and their corrosion resistance. The high costs of these alloys promote their usage as coatings deposited onto cheaper materials. This practice improves the component performance without an excessive increment in price. Cold Spray (CS) deposition is a relatively new technology that could be considered as a real solid-state coating processing method. Consequently, no oxides are formed during CS deposition and the coatings do not lose their potential oxidation resistance. However, mechanical and tribological behaviour of CS materials is highly dependent on the processing parameters and powder feedstock properties. For these reasons, the aim of this work is to evaluate the mechanical properties and the local wear behaviour of high-pressure CS Inconel 625 coatings deposited under different spraying conditions by using different particle size distributions of powders. Nanoindentation tests were carried out on the coatings with a diamond Berkovich tip which determined the elastic modulus and hardness. Additionally, microscratch tests were also conducted to compute the local wear rate through the estimation of the removed volume. The cross profile of the residual grooves was recorded using the same tip as the one used to make scratch tests. These measurements were checked by Atomic Force Microscopy (AFM) analysis. The values obtained by both techniques were similar in the validation tests. The local wear rates were correlated with the mechanical properties and the scratch micromechanisms which were analysed in the scanning electron microscope. Finally, the results obtained were compared with those corresponding to coatings processed by more traditional methods.
Mechanical properties optimization of Cr3C2-NiCr coatings produced by compact plasma spray process
(Elsevier, 2023) Rubino, Felice; Merino, David; Silvestri, Alessia Teresa; Munez, Claudio; Poza, Pedro
Chromium carbides are widely used as functional coatings on steel structures in high-end applications, from energy to marine and aerospace sectors thanks to their corrosion and wear resistance at elevated temperatures. In the present work, a low-power compact plasma spray (CPS) equipment was used to deposit Cr3C2-based cermet coatings on carbon steel substrate. Design of experiment was applied to select and optimize the spraying parameters, namely current, stand-off distance, scanning speed, plasma gas rate and powder feeding rate. ANOVA analysis was conducted to estimate the effect of the spraying variables on morphology and mechanical properties of the coatings and evaluate the optimal spraying condition. Dense and compact coatings were fabricated by using the CPS. By optimizing the processing parameters, coating hardness equal to approximately 600 HV and average thickness ranging around 600 μm were obtained, while the adhesion strength was approximately equal to 14 MPa. Intermediate phases of Cr carbides were produced by the dissolution of the primary Cr3C2 induced by melting and re-solidification of the particles. The presence of weaker carbide phase, inter-lamellae different features and porosity also caused the scattered hardness values observed in the coatings.
Optimization of atmospheric low-power plasma spraying process parameters of Al2O3-50wt%Cr2O3 coatings
(ELSEVIER SCIENCE SA, 2018-09-18) Rico, Álvaro; Salazar, Alicia; Marlen Edith, Escobar; Rodríguez, Jesús; Poza, Pedro
The work is focused on the effect of the processing parameters of Al2O3-50wt%Cr2O3 coatings manufactured by low-power plasma spraying systems on the microstructure, mechanical properties, and tribological behaviour. Design of experiments followed by an optimization process using desirability functions has been applied for the selection of the processing parameters. The results indicate that power is the crucial parameter that controls the microstructure and consequently, the mechanical response of the coatings. At high powers, the highest volume of hard phases is attained, which leads to the highest hardness values and the best wear resistance at high applied loads. On the contrary, at low powers, the highest volume of spinels (tough phases) is observed, resulting in the highest indentation fracture toughness values and the best wear response at low applied loads. Therefore, the mechanical properties are directly related to the contents of the tough and hard phases.
Surface topography analysis in cold spray additive manufacturing
(Elsevier, 2025-03) Sirvent, Paloma; Lozano, Ana; Garrido-Maneiro , Miguel A.; Poza, Pedro; Vaz, Rordolpho F.; Albaladejo-Fuentes, Vicente; Cano, Irene G.
Additive manufacturing, and particularly the cold spray technology for additive manufacturing (CSAM), is fast becoming a key technology to produce components in an efficient and environmentally friendly manner. This method usually requires a final rectification to generate specific surface topographies. The novelty of this paper is related to the capabilities of the CSAM technique to control the surface topography of the samples. Thus, this work investigates the topography of CSAM samples and its correlation with the processing parameters. Pure Al and Ti samples were manufactured following two different deposition strategies: traditional and metal knitting. This last strategy constitutes a promising alternative for CSAM to obtain near-net-final shape components. The topography was analyzed by confocal microscopy considering the form, waviness, and roughness components. Moreover, the microstructure and mechanical properties of the samples were also investigated in order to assure reliable freestanding CSAM deposits. Results showed that the waviness was controlled by the spraying line spacing, and that the waviness and roughness profiles of the metal knitting samples presented the largest wavelengths regardless the material. The metal knitting method generated samples with higher thickness and porosity than the traditional strategy, while the mechanical properties at the local scale were not varied. The study highlights the CSAM technology potential for controlling the deposit’s surface topography