Examinando por Autor "Pastor Muro, Ana"

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Restringido
Corrosion study of a water filter
(Elsevier, 2022-07-22) Valles González, M. P.; Pastor Muro, Ana; García Martínez, María; Instituto Nacional de Técnica Aeroespacial (INTA)
A water filter was inspected in order to determine the origin and chemical nature of several corrosion products on its surface. The metallic material base was analyzed to be a lead brass with a nickel coating of 4–5 µm thickness. The plastic base, as well as the rod and nut, was impregnated by similar deposits whose chemical nature was mainly oxides, carbonates and chlorides, according to the EDX analysis. Some white deposits were observed in the nut and rod, probably corresponding to zinc oxide. These deposits may be formed upstream by the pipe materials or the sediments that the fluid may carried inside the pipe. The absence of a nickel coating leaded to corrosion pits in some areas of the rod and nut. This corrosion has initiated on the surface, and has progressed through the beta phase that was zinc impoverished, to the inner zone of the filter.
Acceso Abierto
Failure analysis of a fractured control presure tube from an aircraft engine
(WASET, 2022-03-22) Valles González, M. P.; González Meije, A.; Pastor Muro, Ana; García Martínez, María; González Caballero, B.
Multiple cases of fuel control pressure tube fractures from aircraft engines have been reported. The aim of the present study is to determine the cause of this tube fracture. The studied set was composed by the mentioned tube, a welded connecting pipe, where the fracture has been produced, and a union nut. The fracture has been produced in one most critical zones of the tube, in a region near to the supporting body of the union nut to the connector. Visual examination and microscopic observation through a stereo microscope of the tube fracture surface has been carried out to determine the macrofractographic features. The results revealed a plastic macrodeformation of the tube, a damaged surface and signs of a possible corrosion process. The material has been chemical, mechanical and microstructural characterized. The results confirmed that specifications were fulfilled. Fracture surface was also inspected by scanning electron microscopy to determine the microfractographic features in order to find out the failure mechanism involved in the fracture. Fatigue striations, which are typical from a progressive fracture by a fatigue mechanism have been observed. The origin of the fracture has been placed in defects located in the outer wall of the tube, leading to a final overload fracture.
Restringido
Long exposure steam oxidation testing and mechanical properties of slurry aluminide coatings for steam turbine components
(Elsevier, 2005-11-21) Osgerby, Steve; Pastor Muro, Ana; Agüero, Alina; Muelas Gamo, Raúl
Important efforts to develop new steels or to protect high creep strength steels in order to allow operation of steam turbines at 650 °C are being carried out world-wide to increase efficiency. Within the European Project “SUPERCOAT” (Coatings for Supercritical Steam Cycles), work has been concentrated in the development of coatings to withstand 50,000–100,000 h of operation at 650 °C under high pressure steam. Aluminide coatings on ferritic–martensitic steels produced by applying an Al slurry followed by a diffusion heat treatment, have shown to be protective at 650 °C under steam for at least 32,000 h of laboratory steam exposure under atmospheric pressure. Although the “as diffused” coatings present through thickness cracks, these do not propagate during exposure to steam or thermal cycling and no new cracks seem to develop. Moreover, no changes in residual stresses could be observed after thermal cycling. Microstructural characterization of samples at different periods of exposures has been carried out by SEM-EDS and XRD. The principal mechanism of coating degradation is loss of Al at the surface due to inwards diffusion. Microhardness as well as Young's modulus and fracture strength were measured using well established techniques. The coatings show reasonable ductility (∼1.6%) when stressed in tension between room temperature and 400 °C which further increases at higher temperatures providing evidence that the coatings should withstand the mechanical conditions likely to be encountered in service.