Monica Campos | Universidad Carlos III de Madrid (original) (raw)

Papers by Monica Campos

... Ana Carnal, José Sicre, Monica Campos, José M. Torralba, Dpt. Materials Sc. and Eng. Universi... more ... Ana Carnal, José Sicre, Monica Campos, José M. Torralba, Dpt. Materials Sc. and Eng. Universidad Carlos III de Madrid, Leganés, Spain Page 2. ... 4, 2004, no. 4, p. 171 [9] Puscas, TM., Signorini, M., Molinari, A., Straffelini, G.: Materials Characterization, vol. 50, 2003, p. 1

The feasibility of fabricating high-density ports from Inconel 718 powder using three-dimensional... more The feasibility of fabricating high-density ports from Inconel 718 powder using three-dimensional printing (3DP) was assessed. Parts were subsequently hot isostatically pressed (HIPed) to achieve full density. After optimization of the particle-size distribution, parts were fabricated by means of the 3D-printing process utilizing two different devices in order to examine the influence of the binder. Printed parts were sintered in high vacuum at 1,563K (1,290°C) or 1,573K (1,300°C) and charactertzed in terms of density and microstructure. Finally, sintered parts were HIPed at 1,473K (1,200°C) and 142 MPa, followed by a second HIPing cycle at 1,483K (1,210°C) and 206 MPa for 3 h in argon to achieve full density.

Oxidation of Metals, 2003

This study examines the resistance to cyclic oxidation at 900°C of two commercial P/M stainless s... more This study examines the resistance to cyclic oxidation at 900°C of two commercial P/M stainless steels—one austenitic (AISI 316L), the other ferritic (AISI 434L)—and of three duplex stainless steels of different compositions. The test results show that the porosity of these materials leads to notable differences between their high-temperature oxidation behavior and that of conventional stainless steels of similar composition. In the case of P/M materials, the resistance to oxidation and the chemical composition of the oxides formed are strongly influenced not only by the degree of porosity of each material, but also by the concentration of Ni in the base metal. In the conditions adopted in the study, ferritic stainless steel was found to provide the best high-temperature oxidation resistance.

Diffusion-alloyed powders have the advantages of the blended powders (high compressibility) but w... more Diffusion-alloyed powders have the advantages of the blended powders (high compressibility) but with a low level of segregation, keeping some of the advantages of the fully alloyed powders. The main problem of conventional Cu-Ni-Mo diffusion-alloyed powders is the use of Ni as raw material (typically nickel carbonyl grade is used to alloy these powders) and its problems as harmful material due to its low particle size. With the aim of drastically reducing the risks of the addition of fine nickel powders, the production of the diffusion-alloyed powders is made with a fully prealloyed Cu-Ni alloy of a bigger size; at the same time, the behaviour of the diffusion paths in the sintering step is modified. In this work, a fully prealloyed 69% Ni-31% Cu (from Höganäs AB) was mixed with plain iron and Fe-0.85% Mo (ASC 100.29 and Astaloy85 grades respectively, Höganäs AB) to obtain diffusion alloyed powders with the following final composition: Fe-2.5% (wt.) NiCu and Fe-0.85%Mo-2.5% (wt.) NiCu. All materials were mixed with 0.6% of graphite, pressed at 700 MPa floating die system and sintered at 1120ºC during 30 minutes in N 2-10%H 2-CH 4 atmosphere. After sintering, steels were quenched in oil from 950ºC. Tempering was made at 250ºC during 40 minutes. All the obtained materials were mechanically tested through tensile test and hardness measurements, as well as proceeding with the metallographic study.

Revista De Metalurgia, 2013

The tolerances of parts produced for the automotive industry are so tight that any small process ... more The tolerances of parts produced for the automotive industry are so tight that any small process variation may mean that the product does not fulfill them. As dimensional tolerances decrease, the material properties of parts are expected to be improved. Depending on the dimensional and material requirements of a part, different production routes are available to find robust processes, minimizing cost and maximizing process capability. Dimensional tolerances have been reduced in recent years, and as a result, the double pressing-double sintering production via ("2P2S") has again become an accurate way to meet these increasingly narrow tolerances. In this paper, it is shown that the process parameters of the first sintering have great influence on the following production steps and the dimensions of the final parts. The roles of factors other than density and the second sintering process in defining the final dimensions of product are probed. All trials were done in a production line that produces synchronizer hubs for manual transmissions, allowing the maintenance of stable conditions and control of those parameters that are relevant for the product and process.

$Research paper thumbnail of Estudio de la degradación de elementos refractarios de alúmina en la sinterización de aceros modificados con Mn$

Boletín de la Sociedad Española de Cerámica y Vidrio

$Research paper thumbnail of Understanding contribution of microstructure to fracture behaviour of sintered steels$

Powder Metallurgy, Dec 15, 2014

ABSTRACT Microstructural features of sintered steels, which comprise both phases and porosity, st... more ABSTRACT Microstructural features of sintered steels, which comprise both phases and porosity, strongly condition the mechanical behaviour of the material under service conditions. Many research activities have dealt with this relationship since better understanding of the microstructure– property correlation is the key of improvement of current powder metallurgy (PM) steels. Up to now, fractographic investigation after testing has been successfully applied for this purpose and, more recently, the in situ analysis of crack evolution through the microstructure as well as some advanced computer assisted tools. However, there is still a lack of information about local mechanical behaviour and strain distributions at the microscale in relation to the local microstructure of these steels, i.e. which phases in heterogeneous PM microstructures contribute to localisation of plastic deformation or which phases can impede crack propagation during loading. In the present work, these questions are addressed through the combination of three techniques: (i) in situ tensile testing (performed in the SEM) to monitor crack initiation and propagation; (ii) digital image correlation technique to trace the progress of local strain distributions during loading; (iii) fractographic examination of the loaded samples. Three PM steels, all obtained from commercially available powders but presenting different microstructures, are examined: a ferritic–pearlitic Fe–C steel, a bainitic prealloyed Fe–Mo–C steel and a diffusion alloyed Fe–Ni–Cu–Mo–C steel, with more heterogeneous microstructure (ferrite, pearlite, upper and lower bainite, martensite and Ni rich ustenite).

International Journal of Powder Metallurgy, 2008

Purpose: The PM industry is in continuous development due to the necessity to increase its potent... more Purpose: The PM industry is in continuous development due to the necessity to increase its potential and competitiveness. This fact and the demand for substituting certain alloying elements used so far, require the addition of new alloying elements and new processes leading to and optimization of costs, strength and tolerances. A different method for introducing Mn into the alloying system is proposed in the present work. Mechanically-blending and mechanically alloying Mn containing master alloys are generated and based on three different steels grades, ASC100.29 (plain iron), Astaloy CrL and Astaloy Mo (pre-alloyed systems).Design/methodology/approach: To profit Mn sublimation effects, small Mn particles, in order to increase the specific surface available to sublimate, must be homogenously added. Different milling times are considered in order to attain the desired master alloys containing 50% of Mn which is diluted in each base powder by normal mixing. New alloying systems were t...

El desarrollo de piezas estructurales de altas prestaciones, en la actualidad está limitado por e... more El desarrollo de piezas estructurales de altas prestaciones, en la actualidad está limitado por el hecho de que los sistemas de aleación están siendo modificados a causa de requerimientos vinculados a directivas medioambientales y al alto precio de las materias primas. La utilización de aleaciones maestras, permite activar los mecanismos de transporte de masa durante la sinterización mediante modificaciones mínimas en la composición (bajo coste) y actuando sobre la densificación, en las propiedades, de forma notable. El Grupo de Tecnología de Polvos (GTP) de la Universidad Carlos III de Madrid, posee experiencia y cualificación en el diseño, desarrollo y fabricación de nuevas aleaciones por atomización de metales fundidos y por molienda de alta energía. Se buscan empresas interesadas en establecer acuerdos de cooperación técnica o de fabricación.

Nowadays, the development of high performance structural parts, is limited by the fact that the a... more Nowadays, the development of high performance structural parts, is limited by the fact that the alloying systems are being modifying by requirements associated to envorimental guideline as well as to the increase in the price of raw materials. The use of masteralloys allows to activate the mass transport processes during sintering with a minimum modification of final composition (low cost) acting on densification, and hence, on final properties. The research group of “Powder Technology” from Carlos III University, has a wide experience and qualification on the design of new alloying systems and in manufacturing the powders by atomization and mechanical alloying techniques. The Group is looking for companies interested in technical cooperation or manufacturing agreement.

Materials Science and Technology, 2014

International Journal of Powder Metallurgy