Browsing by Author "Domínguez-Meister, Santiago"
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Item Corrosion preserving high density plasma treatment of precipitation hardening stainless steel(2018-12-15) Braceras, Iñigo; Ibáñez, Iñigo; Domínguez-Meister, Santiago; Urgebain, Aiala; Sánchez-García, Jose Angel; Larrañaga, Aitor; Garmendia, Iñaki; Tecnalia Research & Innovation; INGENIERÍA DE SUPERFICIES; MATERIALES PARA CONDICIONES EXTREMASSpecialty alloys such as precipitation hardening stainless steels are routinely used in critical applications requiring high strength and corrosion resistance, e.g. in aeronautics, in ground transportation and the biomedical field. Nonetheless, their tribological properties remain poor, while the application of surface treatments results in loss of corrosion resistance. Therefore, typically a not fully satisfactory compromise must be adopted. In the present work, the improvement of tribological features, without loss of corrosion resistance, of the 1.4545 (15-5PH) steel has been explored with the use of high density plasmas. The work has focused on long cylindrical geometries, close to those of real applications. The microstructure and composition of the treated surfaces were studied and the corresponding corrosion resistance stablished. The characteristics of the high density plasmas as well as the sample disposition were key factors in the outcomes, which ranged from fully corroded to corrosion resistant surfaces. Results also showed in certain cases the high density plasmas causing surface cracks followed by local corrosion. Additionally tribological studies demonstrated improvement in wear resistance, and electrical contact resistance (ECR) was found to be a good indicator of the wear phenomena occurring along the tests. An equivalent electric circuit is proposed. Actually ECR could be a useful and simple way of monitoring the surface status and assist in assuring safe and dependable operational lives of the components. In conclusion, treatment conditions of cylindrical 1.4545 (15-5PH) have been defined, which provide with an improved tribological performance, preserving corrosion resistance, with ECR a useful performance monitoring parameter.Item Nitriding of titanium by hollow cathode assisted active screen plasma and its electro-tribological properties(2021-04-15) Domínguez-Meister, Santiago; Ibáñez, Iñigo; Dianova, Anastasia; Brizuela, Marta; Braceras, Iñigo; Tecnalia Research & Innovation; INGENIERÍA DE SUPERFICIESTitanium presents good corrosion resistance, a high strength-to-weight ratio, but poor tribological properties. However, these can be enhanced by nitriding processes. Hollow cathode assisted active screen plasma has proved to be an effective and fast nitriding technique. In this work, the effect of process parameters (hollow cathode induced temperature and plasma intensity, electrical bias…) on the resulting surface microstructure (XRD, SEM/EDS), finishing and hardness of titanium (TiGr4) have been studied. Additionally, the electro-tribological properties have been evaluated on a ball on cylinder reciprocating configuration. The results show that hollow cathode assisted active screen plasma nitriding of titanium can produce titanium nitride surfaces with thicknesses far exceeding those typical in PVD coatings. Moreover, higher plasma processing intensities can generate same layer thicknesses at lower temperatures, minimizing the deleterious effect on grain size growth. Finally, monitoring of the electrical contact resistance can provide valuable information concerning the evolution of the status of the surfaces.Item Solid lubricant behavior of MoS2 and WSe2-based nanocomposite coatings(2017-01-01) Domínguez-Meister, Santiago; Rojas, Teresa Cristina; Brizuela, Marta; Sánchez-López, Juan Carlos; Tecnalia Research & Innovation; INGENIERÍA DE SUPERFICIESTribological coatings made of MoS2 and WSe2 phases and their corresponding combinations with tungsten carbide (WC) were prepared by non-reactive magnetron sputtering of individual targets of similar composition. A comparative tribological analysis of these multiphase coatings was done in both ambient air (30–40% relative humidity, RH) and dry nitrogen (RH<7%) environments using the same tribometer and testing conditions. A nanostructural study using advanced transmission electron microscopy of the initial coatings and examination of the counterfaces after the friction test using different analytical tools helped to elucidate what governs the tribological behavior for each type of environment. This allowed conclusions to be made about the influence of the coating microstructure and composition on the tribological response. The best performance obtained with a WSex film (specific wear rate of 2 × 10−8 mm3 N–1m–1 and a friction coefficient of 0.03–0.05) was compared with that of the well-established MoS2 lubricant material.