Open Access
Chemical and mechanical stability of air annealed cathodic arc evaporated CrAlON coatings
(Elsevier, 2018) Almandoz Sánchez, Eluxka; García Fuentes, Gonzalo; Martínez de Bujanda Carasusán, Javier; Rodríguez Trías, Rafael; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería
This study reports the synthesis and characterization of ternary Cr-Al-O and quaternary Cr-Al-O-N coatings deposited by cathodic arc physical vapour deposition, for various nitrogen and oxygen mass flow ratios during the growth process. The composition, microstructure, indentation hardness and modulus of the films have been characterized by scanning electron microscopy, electron probe micro-analysis, X-ray diffraction, and nanoindentation techniques. The evolution of the microstructure and mechanical properties of the coatings after ambient air annealing from 800 °C up to 1100 °C have been investigated. As the oxygen to nitrogen mass flow increases, the as-deposited coatings exhibit lower hardness, higher roughness, lower crystallinity and a more marked columnar structure. At oxygen to nitrogen mass flow ratios bigger than 10/90, the coatings exhibit a stoichiometry of the type (CrAl)2+εO3−ε. Only the coatings with an oxygen to nitrogen mass flow ratio smaller than 10/90 retained nitrogen in their compositions. In all cases, the coatings developed a cubic fcc lattice structure. After annealing at 1100 °C the resulting microstructure showed a clear dependency upon the initial composition of the films. The evolution of the microstructure during the high temperature tests, as well as the analysis of the nanoindentation hardness, composition and thickness also provided valuable information about the combined effects of the thermal stability and the oxidation of the deposited coatings.
Open Access
Desarrollo de recubrimientos PVD cuaternarios de tipo nitruro, óxido y oxinitruro para aplicaciones de trabajo en caliente
(2017) Almandoz Sánchez, Eluxka; Rodríguez Trías, Rafael; García Fuentes, Gonzalo; Ingeniería Mecánica, Energética y de Materiales; Mekanika, Energetika eta Materialen Ingeniaritza
La tesis consiste en una aportación en el campo de los recubrimientos PVD para aplicaciones en procesos de conformado y moldeo a alta temperatura. Para ello se ha abordado el estudio de una serie de familias de recubrimientos potencialmente capaces de resistir temperaturas de trabajo elevadas manteniendo sus características mecánicas en unos niveles aceptables. Por una parte, se han estudiado recubrimientos cuaternarios TiAlSiN y CrAlSiN, los cuales ven mejorada su resistencia a temperaturas elevadas respecto a los recubrimientos PVD comerciales, TiN y CrN, gracias a la presencia de los elementos Al y Si en su composición. Por otro lado, se ha abordado el estudio de recubrimientos basados en óxidos como el CrAlO y el CrAlON, que tanto en su vertiente monocapa como en la multicapa, son también potencialmente capaces de resistir temperaturas elevadas preservando sus características mecánicas debido a su naturaleza de óxidos. Los recubrimientos se han depositado por PVD arco eléctrico y se han caracterizado mediantes técnicas de SEM, TEM, EDX, GD-OES, XRD. Se han medido también sus propiedades mecánicas y tribológicas mediante microdurómetros, nanoindentadores, y ensayos tribológicos a temperatura ambiente y alta temperatura. Se han estudiado las correlaciones entre parámetros de deposición, microestructura y propiedades y se han comparado los resultados con los reportados por la literatura. Se han realizado, finalmente, pruebas de campo en procesos industriales de inyección de aluminio a alta presión (HPDC) y de sinterizado de cerámicas con el fin de evaluar y validar el comportamiento en servicio de los recubrimientos desarrollados.
Open Access
CrAlON CAE-PVD coatings for oxidation and wear protection of TZM alloys in FAST sintering applications
(Elsevier, 2018) Almandoz Sánchez, Eluxka; Fernández de Ara, Jonathan; Martínez de Bujanda Carasusán, Javier; Rodríguez Trías, Rafael; Institute for Advanced Materials and Mathematics - INAMAT2
In this work CrAlO and CrAlO/CrAlN multilayers deposited by cathodic arc evaporation are evaluated as protective films in metal and ceramic powder FAST sintering tool dies fabricated in titanium-zirconium-molybdenum allows (TZM). The films have been characterised in terms of their composition, microstructure, mechanical properties and thermal stability in air at high temperatures between 800 °C and 1100 °C; in addition the tribological performance has been analysed at room temperature and at 400 °C. The crystalline structure and composition of the CrAlO based coatings are compatible with the formation of a mixture of α-corundum and a cubic fcc (Cr,Al)2O3. The crystalline structure of the multilayer is, on the other hand, dominated by the cubic fcc lattice plane reflections of the CrAlN. The deposited specimens have high hardness, between 25 and 30 GPa, which are stable even after annealing at 1000 °C. Even more, the multilayer coating also exhibited good mechanical stability at 1100 °C. The multilayer coating also exhibited an excellent behaviour against wear at 400 °C. Sintering trials using coated TZM dies have been carried out using Ti90Sn10 and Al2O3 high energy ball milled powders. The experimental results show that the oxide based coating formulations are potentially able to protect the tools from wear, sticking and oxidation of their surfaces. This may allow the use of TZM material as an alternative to other substrates such as graphite.

Almandoz Sánchez, Eluxka

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