Examinando por Autor "Rodrigo, Pilar"

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Additively Manufactured Al/SiC Cylindrical Structures by Laser Metal Deposition
(Mdpi, 2020) Riquelme, Ainhoa; Rodrigo, Pilar; Escalera-Rodríguez, María Dolores; Rams, Joaquín
Preliminary characterization of the microstructure of Al/SiCp composites prepared by Laser Metal Deposition (LMD) was analyzed, and the microhardness and wear behavior of the materials manufactured have been evaluated. It has been determined that the combined e ect of the laser speed and power is decisive for the fabrication process. The microstructure characterization shows that the presence of hygroscopic Al4C3 can be avoided by adding Ti to the composite matrix. The wear behavior of the LMD samples and their microhardness have been compared with Powder Metallurgy samples with the same composition. The LMD samples showed higher hardness and wear resistance.
Carrying Gas Influence and Fabrication Parameters Impact in 3D Manufacturing of In Situ TiN-Ti Composites by Direct Laser Deposition
(Springer, 2022) Sánchez de Rojas Candela, Carmen; Riquelme, Ainhoa; Rodrigo, Pilar; Rams, Joaquín
The difculty of getting a correct distribution of the reinforcement in the metal matrix and the complexity for achieving a good-metallurgy matrix-reinforcement bonding has limited the development of additive manufacturing of metal matrix composites. This research proposes the use of a reactive atmosphere during the fabrication process to obtain titanium matrix composites reinforced with TiN. The relation between the carrying gas and the process parameters used with the presence of porous and defects, the microstructure, and microhardness has been obtained. Nitrogen was used as the carrying gas of the titanium powder. Under laser irradiation, the particles melt and react with nitrogen, resulting in the formation of a titanium matrix composite highly reinforced with TiN. The composite obtained had a microhardness increase between 50 and 100% in comparison with titanium samples fabricated in the same conditions in an argon atmosphere. Three reaction mechanisms have been proposed to take place in the microstructure, depending on the amount of nitrogen in the titanium particles, and its difusion in them during the manufacture.
Characterisation and mechanical properties of Al/SiC metal matrix composite coatings formed on ZE41 magnesium alloys by laser cladding
(Elsevier, 2019) Riquelme, Ainhoa; Rodrigo, Pilar; Escalera-Rodríguez, María Dolores; Rams, Joaquín
Metal matrix composite coatings on light alloys are in high demand in the transport industry to reduce the weight of vehicles without a reduction in mechanical properties. Composite coatings with various mixtures of Al, Si, Ti and SiC could be a good option for this application but the high reactivity between the melted aluminium and the reinforcement must be avoided. This study provides a solution for this problem for laser cladding composite coatings on ZE41 magnesium alloys. The method employed consists of the addition of different alloying elements (silicon or titanium) to the composite matrix to avoid Al4C3 formation. A dilution of magnesium from the substrate in the aluminium coating matrix takes place and it produces an important effect in the matrixreinforcement reactions. The microstructure and mechanical properties of the coatings are analysed. The reaction mechanisms are also determined. Al4C3 formation is avoided and the mechanical properties are improved. Introduction The increased awareness of the need to save energy is one of the most important reasons for the development and research of magnesium alloys. The interest in this topic has increased since the 1990s [1,2] because of the oil crisis. Environmental legislation related to polluting gas emission from transport vehicles is becoming more restrictive. For this reason, the aeronautic and automotive transport sectors have been forced to reduce the weight of their components by employing lighter materials [3–5]. Lights alloys, like magnesium, are attracting high attention due to their reduced density, which provides them with high specific values of stiffness and strength. Nevertheless, the use of these alloys is limited because of their low superficial properties. The superficial property modification in these alloys could increase the variety of applications in which they could be used. This study provides a solution for this problem by fabricating aluminium matrix composite (Al-MMC) coatings on magnesium alloys. In previous research, laser cladding with Al/SiC particles (SiCp) on aluminium alloys was successfully carried out [6]. SiC, in the shape of particles, is an excellent reinforcement
Comparison of Different Additive Manufacturing Methods for 316L Stainless Steel
(MDPI, 2021-10-29) Bedmar, Javier; Riquelme, Ainhoa; Rodrigo, Pilar; Torres, Belén; Rams, Joaquín
In additive manufacturing (AM), the technology and processing parameters are key elements that determine the characteristics of samples for a given material. To distinguish the effects of these variables, we used the same AISI 316L stainless steel powder with different AM techniques. The techniques used are the most relevant ones in the AM of metals, i.e., direct laser deposition (DLD) with a high-power diode laser and selective laser melting (SLM) using a fiber laser and a novel CO2 laser, a novel technique that has not yet been reported with this material. The microstructure of all samples showed austenitic and ferritic phases, which were coarser with the DLD technique than for the two SLM ones. The hardness of the fiber laser SLM samples was the greatest, but its bending strength was lower. In SLM with CO2 laser pieces, the porosity and lack of melting reduced the fracture strain, but the strength was greater than in the fiber laser SLM samples under certain build-up strategies. Specimens manufactured using DLD showed a higher fracture strain than the rest, while maintaining high strength values. In all the cases, crack surfaces were observed and the fracture mechanisms were determined. The processing conditions were compared using a normalized parameters methodology, which has also been used to explain the observed microstructures.
Corrosion Resistance of Al/SiC Laser Cladding Coatings on AA6082
(Mdpi, 2020) Riquelme, Ainhoa; Rodrigo, Pilar; Escalera-Rodríguez, María Dolores; Rams, Joaquín
Aluminum matrix composites reinforced with silicon carbide particles (SiCp) were deposited by laser cladding on AA6082 aluminum alloy. Di erent compositions of the matrix of the composites coating were used and di erent amounts of Si and Ti were added to a base of Al-12Si in order to control the reactivity between molten aluminum and SiCp during laser cladding. The corrosion behavior of the coatings deposited was evaluated in 3.5 wt.% NaCl solution using gravimetric analyses and electrochemical polarization tests. The corrosion products observed were Al(OH)3 and Al2O3, and they formed a layer that limited the evolution of corrosion. However, the presence of discontinuities in it reduced the corrosion resistance of the coating. The corrosion mechanisms were di erent depending on the coating composition. The addiction of Ti to the alloy allowed for better corrosion behavior for the composite coating than that of the aluminum substrate.
Effect of the process parameters in the additive manufacturing of in situ Al/AlN samples
(Elsevier Sci Ltd, 2019) Riquelme, Ainhoa; Rodrigo, Pilar; Escalera-Rodriguez, María Dolores; Rams, Joaquín
Additive manufacturing has revolutionized the manufacturing industry. Researchers have investigated various techniques for increasing the reliability of the metal Additive Manufacturing processes. However, there are few studies about Additive Manufacturing of metal matrix composite components, so, it is necessary increase the research about this topic. In situ Al/AlN composite was synthesized using Direct Laser Deposition equipment in which aluminum powder was deposited through a laser beam using N2 as carrying and reactive gas. This composite powder has been melted and directly deposited layer by layer to form an additive structure. The effect of the laser parameters on the geometry, microstructure and properties of the fabricated structures have been analysed. This allowed the development of a process map for Al and Al/AlN pieces fabricated by Direct Laser Deposition. In situ Al/AlN samples have higher mechanical properties than Al samples.
Evaluation of the Wear Resistance and Corrosion Behavior of Laser Cladding Al/SiC Metal Matrix Composite Coatings on ZE41 Magnesium Alloy
(MDPI, 2021-05-27) Riquelme, Ainhoa; Rodrigo, Pilar; Escalera-Rodriguez, María Dolores; Rams, Joaquín
Aluminum matrix composites reinforced with SiC particles (SiCp) were deposited on ZE41 magnesium substrates by laser cladding in order to improve their tribological performance. Silicon and titanium were added to the matrix in order to avoid Al-SiC reactivity. The addition of these elements to avoid Al4C3 formation during the laser cladding fabrication was successfully explored in previous research, but the effect of these elements on the wear behavior and the corrosion resistance of these coatings has not been studied. During the fabrication process, there is dilution with the substrate that forms an Al-Mg matrix, which has an influence on the wear and corrosion behavior. Electrochemical polarization and impedance measurements in a 3.5% NaCl solution and the dry sliding conditions on a pin-on-disc tribometer were used to evaluate the different compositions of Al/SiCp coatings on the ZE41 magnesium alloy and uncoated ZE41. All of the composite coatings had lower wear rates than the substrate. However, the coatings showed worse corrosion behavior than the ZE41 substrate, although the addition of Si or Ti improves the corrosion behavior and the wear resistance.
Influence of the Feed Powder Composition in Mechanical Properties of AlN-Nano-Reinforced Aluminium Composites Coatings Deposited by Reactive Direct Laser Deposition
(Mdpi, 2020) Riquelme, Ainhoa; Rodrigo, Pilar; Escalera-Rodriguez, María Dolores; García-Fogeda, Pablo; Rams, Joaquín
Aluminium matrix composite coatings reinforced with AlN nanopaticles have been manufactured by direct laser deposition on an AA6082 alloy substrate. The reinforcement of the composite has been generated by the direct nitridation reaction of the feed powder with the carrier gas (N2) heated by an HPDL beam during the fabrication of the coating. The coating obtained consists of nano-sized AlN particles in an aluminium matrix, and the crystalline structure of the obtained AlN depends on the characteristics of the powder used. In this work, the influence of the feed powder composition is studied by comparison among pure aluminium, Al12-Si alloy, and AA6061 alloy, on the formation ofAlNand its crystalline structure. Acorrelationwas established between the temperature distribution reached by the particles, their composition, and the nitridation reaction mechanisms. The effect of the reinforcement was evaluated by comparing the microstructure and mechanical properties (microhardness, nanoindentation) of the composite costing with non-reinforced Al coatings and uncoated AA6082. Al/AlN composite coatings with improved properties were achieved, reaching hardness values that were 65% higher than coatings without reinforcement.
Mg–1Zn–1Ca alloy for biomedical applications. Influence of the secondary phases on the mechanical and corrosion behaviour
(Elsevier, 2020-08-05) Pulido-González, Nuria; Torres, Belén; García-Rodríguez, Sonia; Rodrigo, Pilar; Bonache, Victoria; Hidalgo-Manrique, Paloma; Mohedano, Marta; Rams, Joaquín
An as-cast Mg–1Zn–1Ca alloy has been soundly characterized to be used as a biodegradable material in biomedical applications. Ca and Zn additions have a great influence in the microstructure, mechanical properties and corrosion behaviour of Mg alloys. SEM examinations revealed that most of the Ca and Zn atoms form Mg2Ca and Ca2Mg6Zn3 precipitates, which distribute preferentially along the grain boundaries forming a continuous network of secondary phases. The results of nanoindentation tests show differences in hardness and elastic modulus between the α-Mg matrix and the secondary phases. The results of three-point bending tests shows that cracks propagate following the network formed by the intermetallic compounds at the grain boundaries (GBs). The evolved hydrogen after immersion in Hank’s solution of the alloy has been also estimated, showing a change in the corrosion mechanism after 160 h. The intermetallic compounds act as a barrier against corrosion, so that it progresses through the α-Mg matrix phase.
Microstructural, mechanical and corrosion characterization of an as-cast Mg–3Zn–0.4Ca alloy for biomedical applications
(Elsevier, 2020-06) Pulido-González, Nuria; Torres, Belén; Rodrigo, Pilar; Hort, Norbert; Rams, Joaquín
The as-cast Mg–3Zn–0.4Ca alloy shows a great potential to be used in biomedical applications due to its composition, mechanical properties and biodegradability. Zn and Ca appear naturally in the organism accomplishing vital functions. The alloy consists of an α-Mg matrix and a eutectic composed of α-Mg + Ca2Mg6Zn3. The eutectic product enhances the mechanical properties of the studied alloy, causing strengthening and providing superior hardness values. In this alloy, cracks initiate at the intermetallic compounds and progress through the matrix because of the open network formed by the eutectics. Attending to the corrosion results, the eutectic product presents a noble potential compared to the α-Mg phase. For this reason, the corrosion progresses preferentially through the matrix, avoiding the (α-Mg + Ca2Mg6Zn3) eutectic product, when the alloy is in direct contact to Hank's solution.
Wear behavior of additively manufactured 316L/SiCp composites with up to 60 wt% SiCp
(Elsevier, 2022) Sánchez de Rojas Candela, Carmen; Riquelme, Ainhoa; Rodrigo, Pilar; Torres, Belén; Rams, Joaquín
The wear behavior of 316L composites reinforced with up to 60% SiCp additively manufactured by LaserDirected Energy Deposition (DED) has been studied and the effect of adding different percentages of SiC particles (SiCp) has been evaluated and compared with 316L stainless steel. The wear tests were carried out on the pin-on-disc configuration. The microstructure and microhardness of the samples have been studied, and the friction coefficient, pin and disc mass loss, and wear rate have been correlated with them. The worn surfaces and the corresponding debris were observed under a scanning electron microscope (SEM) and 3D optic profilometer so that the wear mechanisms have been determined. Increasing the SiCp content results in a better wear performance in which the composite mass loss reduces while the disc mass loss increases. Composite with 40 wt% SiCp shows hardness that is five-fold that of the 316L and a ten-fold wear resistance. For 60 wt% SiC content, the presence of graphite also reduced the friction coefficient. The incorporation of SiCp changes the wear mechanisms from adhesive for unreinforced 316L to delamination, abrasive, and oxidative for reinforced composites.
Wear Resistance of Aluminum Matrix Composites' Coatings Added on AA6082 Aluminum Alloy by Laser Cladding
(MDPI, 2021-12-29) Riquelme, Ainhoa; Rodrigo, Pilar; Escalera-Rodríguez, María Dolores; Rams, Joaquin
Ceramic-reinforced metal matrix composites are known for their high wear resistance. A coating based on these materials would be helpful to improve the wear behavior of aluminum alloys. Laser cladding has been used to deposit a coating consisting of an aluminum alloy reinforced with SiC particles on an AA6082 aluminum alloy. Laser cladding is a very energetic technique that causes the SiC particles to react with the molten aluminum to form Al4C3, which degrades the particles and reduces the properties of the coating. The formation of this detrimental compound was successfully achieved with the addition of Silicon and Titanium to the composite matrix. The microstructures of the newly developed material were characterized and the wear behavior was studied under dry sliding conditions on a pin-on-disc tribometer. The relationship between the microstructure and wear behavior was identified. The absence of Al4C3 in the Al40Si/SiC and Al12Si20Ti/SiC coatings’ microstructures resulted in an abrasion mechanism instead of a delamination mechanism. The wear behavior changed along the sliding distances. During the first 200 m of sliding distances, the wear rate of all coatings was lower than the uncoated one due to their higher microhardness. For longer sliding distances, the wear resistance of the uncoated AA6082 was higher than the coated ones due to the formation of a lubricant oxide layer on the AA6082 worn surface. For 1000 m of wear distances, the wear behavior was different for each coating. The wear rate of the Al12Si/SiC coating continued growing due to the delamination mechanism and the presence of Al4C3 that acted as starting crack points. The wear rate of the Al40Si/SiC coating decreased due to the formation of a thin, superficial oxide layer. The wear rate of the Al12SiTi/SiC progressively decreased along the sliding distance to below the substrate wear rate.