Mechanical properties of duplex stainless steel laser joints

[EN] This work presents the influence of welding parameters on the microstructural parameters and mechanical behaviour of welded joints. In doing so, we seek to establish the microstructural changes in the molten area and the heat affected zone, which will define the mechanical properties of the welded joints. This mechanical behaviour is evaluated by means of traction tests on welded test pieces and microhardness scanning of the heat affected zone.The authors would like to express their gratitude to the Asociación de Investigación de Óptica de la Comunidad Valenciana [Community of Valencia Optics Research Association] for the application of the laser welds and to the Spanish Ministry of Science and Technology for its support through Project MAT2001-1123-C03-02.Amigó, V.; Bonache Bezares, V.; Teruel Biosca, L.; Vicente-Escuder, Á. (2006). Mechanical properties of duplex stainless steel laser joints. Welding International. 20(5):361-366. doi:10.1533/wint.2006.3582S36136620

Microstructural control of ultrafine and nanocrystalline WC-12Co-VC/Cr3C2 mixture by spark plasma sintering

The aim of this present work is to study the effect of VC and/or Cr 3C 2 in densification, microstructural control and mechanical behaviour of WC-12Co ultrafine and nanocrystalline mixtures, consolidated by spark plasma sintering at 1100 °C, applying a pressure of 80 MPa in combination with a heating rate of 100 °C min -1. Nanocrystalline and ultrafine mixtures with an average size of 30 nm and 100-250 nm, respectively, with the addition of 1 and 0.5 wt.% of VC/Cr 3C 2 grain growth inhibitors, respectively, were investigated. The density, microstructure, hardness and fracture toughness of the consolidated samples were measured and observed. The addition of VC inhibitor allows an excellent grain growth control keeping microstructures with an average grain size of 154 nm. The hardness values and fracture toughness obtained were about 2000 HV 30 and above 10 MPa m 1/2, respectively. © 2010 Elsevier Ltd and Techna Group S.r.l.The work is supported financially by the Spanish Ministry of Science and Innovation by means of the project MAT 2006-12945-C02. A. Borrell, is grateful to this Ministry for the mobility grant to the Institute of Materials Technology (ITM) of the Polytechnical University of Valencia, Spain.Bonache Bezares, V.; Salvador Moya, MD.; García-Rocha, V.; Borrell Tomás, MA. (2011). Microstructural control of ultrafine and nanocrystalline WC-12Co-VC/Cr3C2 mixture by spark plasma sintering. Ceramics International. 37(3):1139-1142. https://doi.org/10.1016/j.ceramint.2010.11.026S1139114237

Study of erosion behaviour of conventional and nanostructured WC-12Co coatings sprayed by atmospheric plasma

Thermal sprayed WC-Co coatings are used extensively to enhance the wear resistance of a wide range of engineering components. In this paper, erosive resistance of plasma atmospheric sprayed WC-12Co coatings has been evaluated. Solid particle erosion tests were conducted on these coatings at different angles of impact with silica and alumina abrasives of size 250 µm. Coatings have been deposited by using micrometric and nanometric agglomerated powders, employing H2 and He as plasmogen gas. In order to determine the erosion regime (ductile or brittle), the influence of impact angle on the erosion rate has been studied. Optical microscope and FESEM have been used to analyze the eroded surface. The influence of the plasmogen gas and the powder employed on the erosive behaviour of the coating has been evaluated. An attempt to connect the erosive behaviour with mechanical properties and microstructure has been made. Hardness has been determined by means of several measurements of Vickers microhardness; fracture toughness has been estimated through indentation method. Identification of phases has been made by means of X Ray diffractio

Propiedades mecánicas y tribológicas de materiales nanoestructurados de carburo de silicio/nanofibras de carbono

The development of new ceramic/carbon nanostructured materials is a very interesting option from the point of view of the automotive and aerospace industries. Its low density, high mechanical strength, high oxidation resistance and excellent friction behavior allows the use of these composites as functional materials. The aim of this study was to evaluate the influence of carbon nanofibers (CNFs) on the mechanical and tribological behavior of silicon carbide/CNFs nanocomposite obtained by spark plasma sintering technique. The tribological study was carried out in a ball-on-disk apparatus under dry sliding conditions (dry friction) and a fixed load of 15 N. The friction coefficient and wear rate were measured for each composite. Scanning electron microscope was used to analyze wear surface formed. The results show simultaneous improvement of wear behavior and mechanical properties of ceramic materials by incorporating of carbon nanofibers.[ES] : Los materiales compuestos cerámica/carbono poseen excelentes propiedades que los convierten en candidatos idóneos para diversas aplicaciones. Entre otras cabe destacar su empleo en frenos de aviones o coches de competición. Su baja densidad, alta resistencia mecánica, elevada resistencia a la oxidación, excelente comportamiento a fricción y una baja sensibilidad a las condiciones de operación permite utilizar estos compuestos como material funcional. Por todo ello, la obtención de nuevos materiales nanoestructurados cerámica/carbono aparece como una opción muy interesante dada la creciente demanda que existe desde las industrias automovilística y aeronáutica. El objetivo de este trabajo es evaluar la influencia de las nanofibras de carbono (CNFs) en el comportamiento mecánico y tribológico de los nanocompuestos de SiC/CNFs obtenidos mediante la técnica de spark plasma sintering. La caracterización tribológica realizada se ha basado en ensayos de deslizamiento en seco, mediante un dispositivo tipo ball-on-disk. La carga de contacto que se ha utilizado ha sido de 15 N. Las superficies de desgaste se han observado mediante microscopía electrónica de barrido. Los resultados obtenidos demuestran la mejora simultánea del comportamiento al desgaste y de las prestaciones mecánicas del material cerámico al incorporarle las nanofibras de carbono, siendo el coeficiente de fricción muy estable.Borrell Tomás, MA.; Torrecillas, R.; Rocha, VG.; Fernández, A.; Bonache Bezares, V.; Salvador Moya, MD. (2011). Propiedades mecánicas y tribológicas de materiales nanoestructurados de carburo de silicio/nanofibras de carbono. Boletín de la Sociedad Española de Cerámica y Vidrio. 50(3):109-116. doi:10.3989/cyv.152011S10911650

Wear behaviour of WC plasma sprayed coatings wi th micro and nanostructured powders

El objetivo de este trabajo es estudiar el comportamiento a desgaste de distintos recubrimientos de WC sobre acero inoxidable mediante proyección por plasma atmosférico. Se proyectan dos tipos de polvos comerciales con base cobalto (12 %) y níquel (10 %), con el objeto de analizar la influencia de la matriz e incluso del espesor del recubrimiento. Los recubrimientos obtenidos se caracterizan microestructuralmente por microscopía electrónica de barrido y difracción de rayos X. La caracterización tribológica de los recubrimientos se realiza mediante ensayos pin-on-disc contra bolas cerámicas de alúmina (2.400 HV) y nitruro de silicio (1.600 HV), sin lubricación, obteniéndose las tasas de desgaste y la evolución del coeficiente de rozamiento. Las pistas de desgaste y los residuos generados se caracterizaron mediante Microscopía Electrónica de Barrido, MEB. Los resultados muestran diferentes mecanismos de desgaste en cada par de material ensayado en función de la matriz y de la naturaleza de la bola empleada en el ensayo, encontrándose mayores tasas de desgaste con bola de nitruro de silicio. En una segunda fase, se obtienen recubrimientos, con dos polvos base cobalto cuyos tamaños de partícula son micrométrico y nanométrico, respectivamente, con el objetivo de estudiar la influencia del tamaño de partícula inicial sobre las propiedades a desgaste del recubrimiento. Los resultados obtenidos ponen de manifiesto una mayor resistencia al desgaste de los recubrimientos obtenidos con polvos nanoestructurados, bajo condiciones de carga elevadas, mientras que para cargas bajas ambos recubrimientos presentan un comportamiento similar a pesar de las diferencias microestructurales apreciadasThe aim of the present work is the study of wear behaviour of different WC coatings deposited on stainless steel substrate by means of atmospheric plasma spraying (APS). Two types of WC commercial powders, with different metal binder (12% Cobalt and 10% Nickel) have been deposited in order to analyse the influence of the metal matrix and thickness of the coating in tribological properties.The microstructure of the depositions was characterized using scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). On the other hand, tribology characterization of the coatings was made by pin-on-disk wear tests against alumina (2400HV) and silicon nitride (1600HV) ceramic balls, without lubrication. Wear rates and friction coefficient evolution have been calculated. Finally, wear tracks and wear debris have been analysed with the help of SEM.The results of each pair of tested materials show different mechanisms of wear related to the nature of the ball that has been used, obtaining higher wear rates with silicone nitride ball..In a second phase of the study, in order to examine the influence of the initial particle size on the wear properties of the coatings, cobalt based coatings have been analysed with different initial particle size (micrometric and nanometric particles).Results show that nanostructured coatings have higher wear resistance than microstrutured ones for high loads. However for low loads, behaviour is similar in spite of the microstructural differences appreciate

Luces y sombras de las herramientas de generación de contenidos por inteligencia artificial (IA) en grados de ingeniería

[ES] Con el presente estudio del uso de la Inteligencia Artificial (IA) como herramienta para fomentar el pensamiento crítico en los grados de Ingeniería se pretende mostrar al alumno el uso adecuado de herramientas tecnológicas, como la inteligencia artificial, para aumentar y mejorar sus capacidades en el análisis de información y consolidar su razonamiento crítico como parte insustituible de su condición humana. Para ello, los alumnos realizarán diferentes actividades con ayuda del software en distintas asignaturas, siempre bajo la dirección de un profesor. Esto, por un lado, permitirá a los alumnos interactuar con los sistemas de IA para, en base a su criterio, usarlo en la toma de decisiones de acuerdo a las competencias generales y específicas descritas en las guías docentes. Por otro lado, permitirá a los tutores realizar un análisis del impacto que tiene el uso de esta herramienta disruptiva en el entorno académico y prepararlos para un mundo en el que la IA ya es una realidad.[EN] In the present work about the use of Artificial Intelligence (AI) as a tool to promote critical thinking in engineering studies, the aim is to show the students how to use these technological tools to increase and enhance their capacities in the analysis of information and consolidate their critical thinking as an irreplaceable part of their human condition. To study the impact of the use of these AI tools, the students will use a software of AI in different activities monitored by the tutor. This, on the one hand, will allow students to interact with the AI systems and, based on their criteria, use it in decision-making according to the general and specific competencies described in the teaching guides. On the other hand, it will allow the mentors to carry out an analysis of the impact that the use of this disruptive tool has on the academic environment and prepare them for a world in which AI is already a reality.Muñoz Moreno, B.; Riquelme Aguado, A.; Rodrigo Herrero, P.; Sánchez Martínez, M.; Bonache Bezares, V.; Utrilla Esteban, V.; Rams Ramos, J.... (2023). Luces y sombras de las herramientas de generación de contenidos por inteligencia artificial (IA) en grados de ingeniería. Editorial Universitat Politècnica de València. 1338-1348. https://doi.org/10.4995/INRED2023.2023.165841338134

Obtención, procesado y caracterización de carburos cementados CW-Co basados en polvos ultrafinos y nanocristalinos

[EN] The necessity of higher quality tools, due to the increasing competitivity in the machining industry, and in general the need of materials with improved wear resistance, places the hard metal sector in continuous technical renovation. The important improvement of hardness, strength and wear resistance obtained in ultrafine WC-Co grades, as well as the extraordinary properties of nanomaterials, has focused the cemented carbides research in obtaining nanocrystalline powders, and in the development of bulk nanostructured cemented carbides, which remains a technological challenge. In this context, the aim of present research is to contribute on the knowledge of the behaviour sintering of ultrafine and nanocrystalline WC-Co mixtures, and to explore the possibilities of microstructural control that allow manufacturing dense cemented carbides with grain size close to the nanometer scale. Furthermore, the effect of the microstructural refinement in the mechanical behaviour of sintered materials is evaluated. Moreover, due to the poor supply and the high cost of these powders in the market, the fabrication of ultrafine and nanocrystaline WC-Co mixtures by planetary milling is studied. This allows analysing the effect of the powder production method on their densification, microstructural development and final mechanical properties. The results obtained show the problems of the powders fabricated by milling, due to their decarburation, and their fast kinetics of grain growth. Furthermore, the advantages of using nanocrystalline powders, versus the ultrafine ones, on improving the densification and capability of microstructural control, have been demonstrated, allowing a significant increase in the hardness of the sintered samples. The main contribution of the research is the combined use of additives inhibitors and pressure assisted sintering techniques that allow increasing the densification at lower sintering temperature and shorter holding times, thus limiting the grain growth. WC-CoVC / Cr3C2 cemented carbides near fully dense is obtained by SPS and HIP in solid phase at 1100 ºC. The addition of inhibitors, especially VC, is demonstrated to be an efficient method for controlling the grain growth in the solid state, even by rapid sintering processes. The combination of addition of VC and HIP sintering at low temperature has allowed manufacturing near nanostructured materials (120 nm), with an excellent combination of properties, with hardness about 2100 HV30 and fracture toughness values greater than 10 MPa·m1/2. These properties place these materials among the most outstanding cemented carbides of those reported in literature.[ES] La necesidad de herramientas de mayor calidad, debido a la creciente competitividad en el sector del mecanizado, y, en general, de materiales con resistencia al desgaste mejorada, sitúa al sector del duro metal en continua renovación técnica. La importante mejora de dureza, resistencia mecánica y resistencia al desgaste obtenida en grados WC-Co ultrafinos, y las excepcionales propiedades asociadas a los nanomateriales, ha focalizado la investigación de metal duro en la obtención de polvos nanocristalinos, y en el desarrollo de carburos cementados nanoestructurados, que sigue siendo un reto tecnológico. En esta línea, la presente investigación, pretente contribuir al conocimiento del comportamiento durante la sinterización de mezclas WC-Co ultrafinas y nanocristalinas, explorando posibilidades de control microestructural, que permitan obtener carburos cementados densos con tamaño de grano próximo a la escala nanométrica, y evaluar el efecto del refinamiento microestructural en su comportamiento mecánico. Además, dada la escasa oferta en el mercado de estos polvos y su elevado coste, se analiza su fabricación mediante molienda en planetario, lo que permite analizar el efecto de la vía de obtención del polvo en su densificación, desarrollo microestructural, y propiedades finales. Los resultados obtenidos ponen de manifiesto la problemática de los polvos obtenidos por molienda, debido a su decarburación, y su rápida cinética de crecimiento de grano. Además, se ha demostrado las ventajas del uso de polvos nanocristalinos frente a los ultrafinos, en el aumento de la densificación y posibilidades de control microestructural, lo que se traduce en importantes aumentos de dureza de los sinterizados. La principal aportación de la investigación es el empleo combinado de aditivos inhibidores y técnicas de sinterización asistidas por presión, que permiten aumentar la densificación reduciendo temperatura y tiempo de exposición, limitando así el crecimiento de grano. Se ha demostrado que es posible obtener sinterizados WC-Co-VC/Cr3C2 casi 100% densos a 1100 ºC, mediante HIP y SPS, confirmándose, además, la efectividad de los inhibidores. La combinación de adición de VC y sinterización en HIP a baja temperatura, ha permitido obtener materiales casi nanocristalinos (120 nm), con una excelente combinación de propiedades, con durezas de hasta 2100 HV30 y valores de tenacidad superiores a los 10 MPa·m1/2, lo que sitúa a estos materiales entre los carburos cementados más destacados de los publicados en la literatura.[CA] La necessitat de ferramentes de major qualitat, degut a la creixent competitivitat en el sector del mecanitzat, i, en general, de materials amb resistència al desgast millorada, situa el sector del metall dur en contínua renovació tècnica. La important millora de duresa, resistència mecànica i resistència al desgast obtinguda en graus WC-Co ultrafins, i les excepcionals propietats associades als nanomaterials, ha focalitzat la investigació de metall dur en l'obtenció de pols nanocristal·lins, i en el desenvolupament de carburs cementats nanoestructurats, que segueix sent un repte tecnològic. En aquesta línia, la present investigació pretén contribuir al coneixement del comportament durant la sinterització de mescles ultrafines i nanocristal·lines, explorant possibilitats de control microestructural, que permeten obtindre carburs cementats densos amb grandària de gra propera a l'escala nanomètrica i avaluar l'efecte del refinament microestructural en el seu comportament mecànic. A més a més, donada l'escassa oferta en el mercat d'aquests pols i el seu elevat cost, s'analitza la seua fabricació mitjançant mòlta en planetari, la qual cosa permet analitzar l'efecte de la via d'obtenció dels pols en la seua densificació, desenvolupament de la seua microestructura, i propietats finals. Els resultats obtinguts posen de manifest la problemàtica dels pols obtesos per mòlta, degut a la seua decarburació, i la seua ràpida cinètica de creixement de gra. Així mateix, s'han demostrat els avantatges de l'ús de pols nanocristal·lins front als ultrafins, en l'augment de la densificació i possibilitats de control microestructural, el que es tradueix en importants augments de duresa dels sinteritzats. La principal aportació de la investigació és l'emprament combinat d'additius inhibidors i tècniques de sinterització assistides per pressió, que permeten augmentar la densificació reduint temperatura i temps d'exposició, limitant així el creixement de gra. S'ha demostrat que és possible obtindre sinteritzats WC-Co-VC/Cr3C2 quasi 100% densos a 1100 ºC, mitjançant HIP i SPS, confirmant-se, a més, l'efectivitat dels inhibidors. La combinació d'addició de VC i sinterització en HIP a baixa temperatura ha permès obtindre materials quasi nanocristal·lins (120 nm), amb una excel·lent combinació de propietats, amb dureses de fins a 2100 HV30 i valors de tenacitat superiors als 10 MPa·m1/2, la qual cosa situa aquests materials entre els carburs cementats més destacats dels publicats en la literatura.Bonache Bezares, MV. (2016). Obtención, procesado y caracterización de carburos cementados CW-Co basados en polvos ultrafinos y nanocristalinos [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/63222TESI

Friction and wear behaviour of WC-Co-Cr3C2-VC cemented carbides obtained from nanocrystalline mixtures

The effect of adding Cr3C2, VC or a mixture of both as a grain growth inhibitors to cemented carbides obtained from WC-12 wt.%Co nanocrystalline mixtures on the behaviour of friction and dry sliding wear have been studied. All the wear tests were performed on a tribometer with ball on disc configuration, using a WC-6 wt.%Co ball as a counterpart with normal contact loads of 40 and 60 N, sliding distance of 2000 m and a sliding speed of 0.1 m/s. A significant reduction in the wear rates was observed by the effect of the aforementioned additives, in particular for the VC, which showed an increase in the wear resistance of the order of 90%. The analysis of wear and surface damage were correlated to the observed behaviour.The authors would like to thank the Ministry of Education and Science, and the support received through the Projects MAT2006-12945-C03-02 and MAT2009-14144-C03-02, as well as the AECI for the realization of the doctoral thesis by L. Espinosa in the ITM of the UPV.Espinosa, L.; Bonache Bezares, V.; Salvador Moya, MD. (2011). Friction and wear behaviour of WC-Co-Cr3C2-VC cemented carbides obtained from nanocrystalline mixtures. Wear. 272(1):62-68. https://doi.org/10.1016/j.wear.2011.07.012S6268272

Fabrication of ultrafine and nanocrystalline WC-Co mixtures by high energy milling

[EN] In this work ultrafine and nanocrystalline WC-Co mixtures were obtained by low energy milling in planetary ball mill. The effect of the processing conditions on the reduction and distribution of the grain sizes and the internal strains level were studied. The characterisation of the powder mixtures was performed by means of scanning and transmission electron microscopy and X-ray diffraction analysis. Observations through SEM and TEM images showed a particle size below 100 nm, after milling. The X-ray diffraction profile analysis revealed a WC phase refined to a crystallite size of 19 nm. The mixtures obtained have been consolidated and mechanical and microstructurally characterised. The results show improvements in resistant behaviour of the material consolidated from nanocrystalline powders, in spite of the grain growth experienced during the sintering. The best results were found for the material obtained by wet milling during 100 h, which presents values of hardness higher than 1800 HV. © 2011 Institute of Materials, Minerals and Mining.This work has been supported by CICYT, Spain, through project no. MAT2006-12945-C03-02.Bonache Bezares, V.; Salvador Moya, MD.; Busquets Mataix, DJ.; Segovia-López, F. (2009). Fabrication of ultrafine and nanocrystalline WC-Co mixtures by high energy milling. Powder Metallurgy. 54(3):214-221. https://doi.org/10.1179/174329009X44932321422154

Preparation and spray drying of Al2O3-TiO2 nanoparticle suspensions to obtain nanostructured coatings by APS

[EN] Al2O3-TiO2 coatings were deposited on austenitic stainless steel coupons from nanostructured powders by atmospheric plasma spraying (APS). Commercial suspensions of nanosized Al2O3 and TiO2 particles were used as starting materials. Mixtures of these suspensions and of more concentrated suspensions of Al2O3 and TiO2 were then agglomerated into plasma sprayable feedstock. Agglomeration was performed by spray drying, followed by consolidation thermal treatment. These powders were successfully deposited, yielding coatings that were well bonded to the substrates. The coating microstructure thus consisted of semi-molten feedstock agglomerates surrounded by fully molten particles that acted as binders. Agglomerates from suspensions with higher solids contents yielded coatings with lower porosity and fewer semi-molten areas. (C) 2010 Elsevier B.V. All rights reserved.This work has been supported by the Spanish Ministry of Science and Innovation (projects MAT2006-12945-C03-01-02 and CIT-420000-2008-2), and the Institute of Small and Medium-sized Enterprise (IMPIVA) of the Autonomous Government of Valencia through the European Social Fund (ESF) Operational Programme for the Valencia Region 2007–2013 and a Complementary Action (ACOMP/2009/221).Sánchez, E.; Moreno, A.; Vicent, M.; Salvador Moya, MD.; Bonache Bezares, V.; Klyatskina ., E.; Santacruz, I.... (2010). Preparation and spray drying of Al2O3-TiO2 nanoparticle suspensions to obtain nanostructured coatings by APS. Surface and Coatings Technology. 205(4):987-992. https://doi.org/10.1016/j.surfcoat.2010.06.002S987992205