Microstructural and XRD analysis and study of the properties of the system Ti-TiAl-B4C processed under different operational conditions

High specific modulus materials are considered excellent for the aerospace industry. The system Ti-TiAl-B4C is presented herein as an alternative material. Secondary phases formed in situ during fabrication vary depending on the processing conditions and composition of the starting materials. The final behaviors of these materials are therefore difficult to predict. This research focuses on the study of the system Ti-TiAl-B4C, whereby relations between microstructure and properties can be predicted in terms of the processing parameters of the titanium matrix composites (TMCs). The powder metallurgy technique employed to fabricate the TMCs was that of inductive hot pressing (iHP) since it offers versatility and flexibility. The short processing time employed (5 min) was set in order to test the temperature as a major factor of influence in the secondary reactions. The pressure was also varied. In order to perform this research, not only were X-Ray Diffraction (XRD) analyses performed, but also microstructural characterization through Scanning Electron Microscopy (SEM). Significant results showed that there was an inflection temperature from which the trend to form secondary compounds depended on the starting material used. Hence, the addition of TiAl as an elementary blend or as prealloyed powder played a significant role in the final behavior of the TMCs fabricated, where the prealloyed TiAl provides a better precursor of the formation of the reinforcement phases from 1100 °C regardless of the pressur

Fabricación mediante innovadoras técnicas pulvimetalúrgicas de materiales compuestos de matriz ligera

Hoy en día el interés por desarrollar nuevos materiales que satisfagan las necesidades tecnológicas, conlleva a un estudio continuo en la innovación de los procesos de fabricación. La ventaja que ofrecen las técnicas pulvimetalúrgicas de procesado en caliente convencional (HP) y directa (dHP), suponen un ahorro en tiempo que puede favorecer la viabilidad de nuevos materiales fabricados por estas técnicas El potencial que presentan en cuanto a sus propiedades los materiales compuestos de matriz de titanio (TMCs), es muy valorado por el sector aeroespacial. La gran limitación de uso de estos materiales en su aplicación en otros sectores se debe en gran medida al alto coste. La línea de investigación creada por este grupo en colaboración con la empresa austríaca RHP-Technology, promueve el estudiofabricación-caracterización de TMCs fabricados mediante técnicas pulvimetalúrgicas avanzadas de compactación en caliente. Esta colaboración ofrece la posibilidad de producir materiales a la carta desde un punto de vista pulvimetalúrgico. Los materiales estudiados principalmente son materiales compuestos de matriz titanio (TMCs) reforzados con partículas cerámicas como son el boro amorfo (B), el carburo de boro (B4C) y el diboruro de titanio (TiB2), con el objetivo de promover reacciones entre la matriz de titanio y las partículas de cerámicos que consoliden nuevos compuestos que actúan reforzando la matriz in situ.Nowadays, the interest in developing novel materials to achieve the technological needs, leads to an ongoing study on innovation of manufacturing processes. The advantages of conventional Hot Pressing technique (HP) and direct Hot Pressing (dHP) involve savings in time in order to promote the viability of new materials manufactured by hot consolidation processes. Titanium Metal matrix Composites (TMCs) offer interesting properties, which are highly valued by the aerospace sector. However, there are some use limitations of these materials in other sectors due to their high cost. The research created by this group in collaboration with the Austrian research-company RHP-Technology, promotes the study-manufacturingcharacterization of these TMCs. This collaboration provides the possibility of manufacturing materials “à la carte” from a point of view of Powder Metallurgy (PM). The materials studied are primarily TMCs reinforced with ceramic particles as boron amorphous (B), boron carbide (B4C) and titanium diboride (TiB2). By the addition of these ceramic materials to the matrix, in situ reactions between the matrix and the ceramic reinforcement are expected. In this respect, the titanium matrix becomes reinforced

Estudio comparativo del comportamiento de diversos materiales de refuerzo en matrices de titanio fabricados mediante compactación por sinterización rápida

Regarding titanium matrix composites (TMCs), their properties strongly depend on the reinforcement material employed for their manufacturing; this may lead to a multitude of investigations on TMCs. Considering the diverse typology of the reinforcement, six types of ceramic particles were tested in this investigation: B₄C, SiB₆ , TiB₂ , TiC, TiN, and BN. In order to compare their behaviour and their own influence on the properties of the TMCs, the same ratio was employed in the starting materials, 30% volume. Among the techniques for developing TMCs, a significant number of authors propose Powder Metallurgy as a favourable route. In this framework, the novel Rapid Sinter Pressing technique was employed to perform the present study, due to its flexibility, repeatability, and reproducibility, as well as short-run cycle times. The processing temperature (930 °C) was set with the intention of evaluating how the reinforcements behave differently depending on their reactivity with the Ti matrix. In this regard, the main objective of the research was to carry out a comparison on the behaviour of seven TMCs fabricated with similar operational parameters via RSP.En cuanto a los materiales compuestos de base titanio (TMC), sus propiedades dependen en gran medida del material de refuerzo empleado para su fabricación; dando lugar a una gran diversidad de investigaciones sobre los TMCs. Considerando la diversa tipología del refuerzo, en este estudio se trabajó con seis tipos de partículas cerámicas: B₄C, SiB₆,TiB₂ , TiC, TiN y BN. Para poder comparar su comportamiento e influencia sobre las propiedades de los TMCs, se empleó siempre la misma proporción con respecto al material de partida, 30% en volumen. Entre las técnicas que se conocen para desarrollar TMCs, la pulvimetalurgia ha sido propuesta como una vía favorable por un número significativo de autores. En este marco, para la realización del presente estudio, se utilizó la novedosa técnica Rapid Sinter Pressing, debido a su flexibilidad, repetibilidad y reproducibilidad, así como a sus reducidos tiempos de ciclo. La temperatura de procesamiento (930 °C) se estableció con la intención de evaluar cómo los refuerzos afectan de diferente manera, en función de su reactividad con la matriz de Ti. En este sentido, el objetivo principal de esta investigación ha sido realizar una comparativa del comportamiento de siete TMCs fabricados vía de Compactación por Sinterización Rápida (Rapid Sinter Pressing) bajo las mismas condiciones de procesado.Universidad de Sevilla VI PPIT-2020-I.

Sinterability, Mechanical Properties and Wear Behavior of Ti3SiC2 and Cr2AlC MAX Phases

MAX phases are a promising family of materials for several demanding, high-temperature applications and severe conditions. Their combination of metallic and ceramic properties makes MAX phases great candidates to be applied in energy production processes, such as high temperature heat exchangers for catalytic devices. For their successful application, however, the effect of the processing method on properties such as wear and mechanical behavior needs to be further established. In this work, the mechanical and wear properties of self-synthesized Ti3SiC2 and Cr2AlC MAX phase powders consolidated by different powder metallurgy routes are evaluated. Uniaxial pressing and sintering, cold isostatic pressing and sintering and hot pressing were explored as processing routes, and samples were characterized by analyzing microstructure, phase constitution and porosity. Wear behavior was studied by reciprocating-sliding tests, evaluating the wear rate by the loss of material and the wear mechanism.The authors would like to thank the funding provided for this research by the Regional Government of Madrid (Dra. Gral. Universidades e Investigación) through the project P2018/NMT4411 (ADITIMAT-CM), and the Spanish Government through the projects PID2019-106631GB-C43 and RTC2019-007049-4

Influence of sintering temperature on the microstructure and mechanical properties of in situ reinforced titanium composites by inductive hot pressing

This research is focused on the influence of processing temperature on titanium matrix composites reinforced through Ti, Al, and B4C reactions. In order to investigate the effect of Ti-Al based intermetallic compounds on the properties of the composites, aluminum powder was incorporated into the starting materials. In this way, in situ TixAly were expected to form as well as TiB and TiC. The specimens were fabricated by the powder metallurgy technique known as inductive hot pressing (iHP), using a temperature range between 900 °C and 1400 °C, at 40 MPa for 5 min. Raising the inductive hot pressing temperature may affect the microstructure and properties of the composites. Consequently, the variations of the reinforcing phases were investigated. X-ray diffraction, microstructural analysis, and mechanical properties (Young’s modulus and hardness) of the specimens were carried out to evaluate and determine the significant influence of the processing temperature on the behavior of the compositesJunta de Andalucía. TIC-752

Effect of processing atmosphere and secondary operations on the mechanical properties of additive manufactured AISI 316L stainless steel by Plasma Metal Deposition

Plasma metal deposition (PMD) is an interesting additive technique whereby diverse materials can be employed to produce end parts with complex geometries. This study investigates not only the effects of the manufacturing conditions on the final properties of 316L stainless steel specimens by PMD, but it also affords an opportunity to study how secondary treatments could modify these properties. The tested processing condition was the atmosphere, either air or argon, with the other parameters having previously been optimized. Furthermore, two standard thermal treatments were conducted with the intention of broadening knowledge regarding how these secondary operations could cause changes in the microstructure and properties of 316L parts. To better appreciate and understand the variation of conditions affecting the behavior properties, a thorough characterization of the specimens was carried out. The results indicate that the presence of vermicular ferrite (δ) varied slightly as a consequence of the processing conditions, since it was less prone to appear in specimens manufactured in argon than in air. In this respect, their mechanical properties suffered variations; the higher the ferrite (δ) content, the higher the mechanical properties measured. The degree of influence of the thermal treatment was similar regardless of the processing conditions, which affected the properties based on the heating temperature.European Union Horizon 2020 Program (H2020) grant agreement no 768612Universidad de Sevilla (España) VI PPIT-2019-I.

Processing by Additive Manufacturing Based on Plasma Transferred Arc of Hastelloy in Air and Argon Atmosphere

This research was carried out to determinate the effect of the atmosphere processing conditions (air and argon) and two specific thermal treatments, on the properties of specimens made from the nickel-based alloy Hastelloy C-22 by plasma transferred arc (PTA). Firstly, the additive manufacturing parameters were optimized. Following, two walls were manufactured in air and argon respectively. Afterwards, a determinate number of specimens were cut out and evaluated. Regarding the comparison performed with the extracted specimens from both walls, three specimens of each wall were studied as-built samples. Furthermore, a commonly used heat treatment in Hastelloy, with two different cooling methods, was selected to carry out additional comparisons. In this respect, six additional specimens of each wall were selected to be heat treated to a temperature of 1120 °C for 20 min. After the heat treatment, three of them were cooled down by rapid air cooling (RAC), while the other three were cooled down by water quenching (WQ). In order to study the influence degree of the processing conditions, and how the thermal treatments could modify the final properties of the produced specimens, a detailed characterization was performed. X-ray diffraction and microstructural analyses revealed the phases-presence and the apparition of precipitates, varying the thermal treatment. Moreover, the results obtained after measuring mechanical and tribological properties showed slight changes caused by the variation of the processing atmosphere. The yield strength of the extracted specimens from the two walls achieved values closer to the standards ones in air 332.32 MPa (±21.36 MPa) and in argon 338.14 MPa (±9 MPa), both without thermal treatment. However, the effect of the cooling rate resulted as less beneficial, as expected, reducing the deformation properties of the specimens below 11%, independently of the air or argon manufacturing atmosphere and the cooling rate procedure.Universidad de Sevilla (España) PPIT-2018-I.

Analysis of the Influence of Starting Materials and Processing Conditions on the Properties of W/Cu Alloys

In this work, a study of the influence of the starting materials and the processing time used to developW/Cu alloys is carried out. Regarding powder metallurgy as a promising fabrication route, the difficulties in producingW/Cu alloys motivated us to investigate the influential factors on the final properties of the most industrially demanding alloys: 85-W/15-Cu, 80-W/20-Cu, and 75-W/25-Cu alloys. Two different tungsten powders with large variation among their particle size—fine (Wf) and coarse (Wc) powders—were used for the preparation ofW/Cu alloys. Three weight ratios of fine and coarse (Wf:Wc) tungsten particles were analyzed. These powders were labelled as “tungsten bimodal powders”. The powder blends were consolidated by rapid sinter pressing (RSP) at 900 C and 150MPa, and were thus sintered and compacted simultaneously. The elemental powders andW/Cu alloys were studied by optical microscopy (OM) and scanning electron microscopy (SEM). Thermal conductivity, hardness, and densification were measured. Results showed that the synthesis ofW/Cu using bimodal tungsten powders significantly affects the final alloy properties. The higher the tungsten content, the more noticeable the effect of the bimodal powder. The best bimodalWpowder was the blend with 10 wt % of fine tungsten particles (10-Wf:90-Wc). These specimens present good values of densification and hardness, and higher values of thermal conductivity than other bimodal mixtures.Junta de Andalucía TIC-752

Study of the Influence of TiB Content and Temperature in the Properties of In Situ Titanium Matrix Composites

This work focuses on the study of the microstructure, hardening, and stiffening effect caused by the secondary phases formed in titanium matrices. These secondary phases originated from reactions between the matrix and boron particles added in the starting mixtures of the composites. Not only was the composite composition studied as an influencing factor in the behaviour of the composites, but also different operational temperatures. Three volume percentages of boron content were tested (0.9 vol %, 2.5 vol %, and 5 vol % of amorphous boron). The manufacturing process used to produce the composites was inductive hot pressing, which operational temperatures were between 1000 and 1300º C. Specimens showed optimal densification. Moreover, microstructural studies revealed the formation of TiB in various shapes and proportions. Mechanical testing confirmed that the secondary phases had a positive influence on properties of the composites. In general, adding boron particles increased the hardness and stiffness of the composites; however rising temperatures resulted in greater increases in stiffness than in hardnes

Estudio preliminar de los parámetros de fabricación en las propiedades finales de piezas de titanio comercialmente puro con geometrías sencillas producidos mediante la técnica de “additive manufacturing”

La necesidad de fabricar piezas de geometrías complejas empleando materiales ligeros con altas propiedades, en el sector aeroespacial conlleva al uso de técnicas cada vez más flexibles y con mayor complejidad técnica. Este es el caso de los procesos de fabricación aditiva capa por capa (Additive Manufacturing, AM). La posibilidad de diseñar piezas partiendo de diseños en 3D, llevándolas a una realidad física, la aventaja frente a otras técnicas de fabricación convencionales. En el presente trabajo, se ha desarrollado un estudio preliminar en piezas de titanio comercialmente puro, fabricadas mediante AM, en particular la técnica de “Plasma Transferred Arch”, bajo diferentes parámetros de fabricación. Dichas piezas se han fabricado a partir de un sustrato de titanio sobre el cual se han ido depositando capa a capa de material (titanio) de una forma específica. El objetivo de dicho estudio es evaluar las posibles diferencias en las piezas de titanio fabricadas con estas geometrías tan sencillas similares a un cordón de soldadura. Desde un punto de vista cualitativo y cuantitativo se han comparado entre sí dichas piezas; de dichas comparativas se ha podido observar la gran influencia que tienen los parámetros de fabricación como el arco de transferencia en los especímenes fabricados.The need to manufacture complex geometry pieces using lightweight materials with high properties, leads in the aerospace sector to the use of techniques increasingly flexible with greater technical complexity. This is the case of Additive Manufacturing processes (AM). The possibility of designing pieces based on 3D designs, taking them into a physical reality, is its main advantage over other conventional manufacturing techniques. In the present work, a preliminary study has been developed on commercially pure titanium pieces, manufactured by means of AM, the “Plasma Transferred Arch” technique, under different manufacturing parameters. The substrate was made from titanium, on which titanium layers were deposited, one by one, in a specific disposition. The objective of this study is to evaluate the possible differences in the titanium pieces manufactured with these simple geometries similar to a weld bead. From a qualitative and quantitative point of view, these pieces have been compared; it is possible to observe the great influence that manufacturing parameters have, as the transferred arc, in the manufactured specimens