A. Rico

Roughness Effect on the Mechanical Properties of Ceramic Materials Measured from Nanoindentation Tests

An experimental study was performed to evaluate the roughness effect on the determination of hardness and Young´s modulus of ceramic materials from nanoindentation tests. Several specimens polished at various stages were tested at different peak load values. Local roughness measurements have been done by means of atomic force microscopy. Results indicate that roughness and size effects are joined. Proportional Specimen Resistant Modified model (PSRM) was applied to avoid the scale effect, isolating the roughness influence. Indentations where the average roughness-elastic displacement ratio is lower than a critical value are needed to get consistent results.

Wear resistance of cold sprayed Al alloys for aeronautical repairs

ABSTRACT Al–Cu alloys, like Al 2024, and Al–Si alloys, like Al F357 and Al C355, are used in aeronautic gearboxes and fuselage parts operating in severe conditions. It is necessary to develop maintenance and overhaul technologies to extend the life of metallic components used in the aeronautical sector. Cold Spray (CS) could be an alternative as it is real solid-state processing technique. However, the repaired component should exhibit similar properties as the original substrate. This paper evaluates the wear performance of Al coatings CS onto the same Al substrates in sliding and oscillating conditions. The results were compared with the corresponding substrates. The wear rate of coatings processed using new conditions, developed to enhance the coatings performance, was similar or smaller than that measured in the substrate bulk alloys. For Al 2024 and Al C355 CS could be used for repairing, from the tribological point of view.

Hardness and Young´s Modulus Determination of Nanostructured Alumina-Titania Coatings

It has been generally accepted that a nanostructured material exhibits better properties than conventional ones. Nanostructured ceramic coatings fabricated by plasma spray have been developed for a wide variety of applications where a surface protection is required. Alumina - titania coatings are usually used as protective layers in many industrial applications requiring a high wear resistance during dry sliding contact. In this work, nanostructured and conventional Al2O3 – 13% TiO2 coatings deposited via atmospheric plasma spray were compared. Mechanical characterization was carried out using depth sensing indentation to determine hardness and Young´s modulus of the coatings. Size independent properties can be determined after considering geometrical factors such as tip rounding and indenter deformation. Nanostructured coatings show slightly better mechanical properties than conventional coatings.