Facultad Regional Concep. del Uruguay

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Author: search.filters.author.Forsich, ChristianHas files: Yes

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    Friction and wear of a-C:H and a-C:H:Si coatings sliding against different counterpart materials under dry and moist environments
    (2024-05-19) Delfín, Francisco Andrés; Jeoffrey, Jecozale; Schachinger, Manuel; Forsich, Christian; Brühl, Sonia Patricia; Heim, Daniel
    The self-lubricating effect of DLC coatings is a very well-known feature, although they have yet to occupy a substantially influential position in mainstream tribological applications. This objective is increasingly critical due to the escalating worldwide focus on achieving energy efficiency, lowering fuel consumption and cutting environmentally harmful emissions. To reach these milestones, a deeper understanding of DLC coatings is required, namely regarding the intricate relationship of friction and wear rates within diverse tribosystems, where parameters such as relative humidity and the material of the counter body show decisive influence. In this work, DLC coatings were deposited using a modified commercially available PA-CVD system on AISI 4140 steel. Two kind of coatings were produced, a-C:H and a-C:H:Si, at temperatures of 450 °C and 550 °C. Process gas consisted of a mixture of argon, acetylene, and HMDSO as silicon precursor. Characterization was carried out by means of nanoindentation, Raman spectroscopy, as well as GDOES and EDX. Tribological behavior was evaluated by means of Pin-on-Disk, using the coated sample as the disk, a 12 N normal load, a speed of 0.4 m/s and a total sliding distance of 2000 m. Counterparts were 6 mm balls, of which three different materials were used: AISI 52100 bearing steel, Al2O3 and Si3N4. Test chamber was conditioned using forced air recirculation and beakers containing either water or regenerated silica gel to create a humid or a dry environment, respectively. Friction coefficient was registered during the entire test. The wear track was evaluated with optical and confocal microscopy, as well as SEM/EDX and Raman spectroscopy. Hardness and elastic modulus increased with deposition temperature, and the values were doubled with silicon doping. However, a lower friction coefficient and wear volume loss were found in Si-free samples. In general, the coatings showed varied responses to the different environments and counterparts: a-C:H showed oxidation with higher humidity, whereas a-C:H:Si exhibited high wear in the drier ambient, producing several peaks in the friction coefficient during the test. The steel counterpart exhibited a lubricious oxide layer that helped reduce the friction coefficient, thus performing better in the humid environment. The Si3N4 counterpart showed the highest adhesion when sliding against a-C:H:Si, although a rather low friction coefficient and wear was shown when testing the Si-free samples.
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    Barrier coatings deposited via PA-CVD and MS-PVD on recyclable polymer foils for food packaging applications
    (2024-09-02) Delfín, Francisco Andrés; Forsich, Christian; Schachinger, Manuel; Augl, Stefan; Brühl, Sonia Patricia; Burgstaller, Cristoph; Heim, Daniel
    Plastic litter has become the predominant contaminant in our lands and oceans. Prioritizing waste recycling is essential to halt this ecologically damaging problem. However, the recycling process is hindered when products like food packaging are made of several layers of different polymers co-extruded together to have acceptable barrier properties. This issue can be addressed by depositing thin coatings using plasma-assisted techniques on single-layer polymer foils, to achieve comparable resistance against water and oxygen permeation. Given the nanometric thickness of these coatings, recycling could be potentially carried out without any inconvenience.
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    Análisis del comportamiento tribológico de recubrimientos tipo DLC en diferentes condiciones de humedad relativa
    (Instituto de Investigaciones en Ciencia y Tecnología de Materiales., 2022-05-02) Delfin, Francisco Andrés; Brühl, Sonia Patricia; Forsich, Christian; Heim, Daniel
    En este trabajo se utilizaron muestras de acero de media aleación AISI 4140 recubiertas con DLC blando tipo a-C:H:Si en un reactor comercial PACVD, utilizando acetileno como precursor de carbono y hexametildisiloxano (HMDSO) para aportar silicio como dopante. Se realizaron deposiciones a diferentes temperaturas y variando la potencia del plasma. Las propiedades mecánicas fueron medidas con nanoindentación. Las muestras se ensayaron en condiciones de desgaste por deslizamiento en un contraparte, en tres diferentes condiciones de humedad: seco, ambiente y húmedo. Se utilizó una carga normal de 12 N, una distancia recorrida de 1000 m y una velocidad tangencial de 0,2 m/s. El coeficiente de fricción fue medido de forma continua y se analizó el desgaste en la bolilla mediante microscopio óptico y electrónico con EDS. El desgaste en la muestra fue determinado con microscopía confocal y se realizó análisis con microscopio óptico, SEM/EDS y espectroscopía Raman. Las muestras que contenían silicio presentaron una pérdida de volumen por desgaste de hasta 80 veces superior a las muestras sin contenido de silicio. El coeficiente de fricción de estas últimas fue del orden de 0,05 en las condiciones más secas, mientras que las Si-DLC alcanzaron este valor en condiciones de alta humedad. Para las muestras sin silicio, el desgaste aumentó a medida que se incrementaba la humedad ambiental, mientras que, en las muestras dopadas con silicio, el comportamiento fue a la inversa.
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    Comportamiento mecánico del acero AISI 316L recubierto con a : C-H-Si previamente nitrurado
    (2014-10-21) Dalibón Bähler, Eugenia Laura; Brühl, Sonia Patricia; Heim, Daniel; Forsich, Christian
    El acero inoxidable AISI 316L es ampliamente usado en la industria química y alimenticia por sus buenas propiedades anticorrosivas, sin embargo presenta baja resistencia al desgaste. Para mejorar las propiedades tribológicas se pueden utilizar técnicas asistidas por plasma, tratamientos de difusión y/o recubrimientos. Los recubrimientos de carbono amorfo a:C-H-Si tienen bajo coeficiente de fricción y buena resistencia al desgaste. Además, son químicamente inertes, aunque presentan problemas de adhesión cuando son depositados sobre metales. En este trabajo se estudió el comportamiento mecánico y la adhesión de un recubrimiento a:C-H-Si tipo soft depositado por PACVD sobre el acero inoxidable AISI 316L nitrurado (muestra dúplex) y sin nitrurar (muestra recubierta). Los recubrimientos fueron caracterizados por EDS y Raman. Se midió la dureza y el módulo elástico utilizando nanoindentación. La microestructura de la capa nitrurada y de los recubrimientos fue analizada por MO, SEM-FIB y DRX. Se realizaron ensayos de pin on disk y de deslizamiento recíproco. Se evaluó la adhesión por indentación Rockwell C y Scratch Test. Los recubrimientos de a:C-H-Si presentaron un contenido de hidrógeno mayor al 40 % y su espesor fue de 20 μm, alcanzaron una dureza de aproximadamente 13 GPa y un módulo elástico de 73 GPa. Estos recubrimientos presentaron un coeficiente de fricción inferior a 0,2 y mejoraron la resistencia al desgaste con respecto al acero sin tratar. La profundidad de las huellas en los ensayos de deslizamiento recíproco fue 6 veces menor, independientemente del tratamiento de nitruración previo. El pretratamiento de nitruración tuvo influencia en la adhesión, ya que la carga crítica fue de 16,2 N en la muestra dúplex y de 9,6 N en la sólo recubierta. En el ensayo de indentación Rockwell C, la muestra dúplex presentó mejor adhesión que la muestra sólo recubierta.
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    Characterization of thick and soft DLC coatings deposited on plasma nitrided stainless steel
    (2014-09-15) Brühl, Sonia Patricia; Dalibón Bähler, Eugenia Laura; Heim, Daniel; Forsich, Christian
    Thick and soft DLC coatings were deposited by PACVD with a DC pulsed discharge on nitrided and non nitrided austenitic stainless steel. The films were characterized by EDS and Raman, hardness was assessed with nanoindenter and the microstructure was analyzed by Optical Microscopy, SEM and XRD.
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    Tribological behavior of thick and soft DLC coatings
    (2015-05-13) Dalibón Bähler, Eugenia Laura; Heim, Daniel; Forsich, Christian; Brühl, Sonia Patricia
    Austenitic stainless steels are widely used in industry due to their good corrosion resistance; however, they present poor mechanical properties. Different coatings such as DLC “Diamond Like Carbon” can be used in order to improve surface properties. According to the sp3/sp2 ratio and the hydrogen content, DLC coatings can be classified in hard DLC or soft DLC. These coatings have low friction coefficient, good wear resistance and chemical inertia; however, they present adhesion problems when they are deposited on metallic substrates. For this reason, the plasma nitriding previous to the DLC coating deposition could be convenient. Although there are several publications about DLC coated and nitrided stainless steels, not many contributions have been found in the literature about soft and thick coatings. In this work, the tribological behavior and adhesion of thick and soft DLC coatings deposited on nitrided and non-nitrided austenitic stainless steels were studied.
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    Mechanical and corrosion behavior of thick and soft DLC coatings
    (2015-10-09) Dalibón Bähler, Eugenia Laura; Escalada, Lisandro; Simison, Silvia; Forsich, Christian; Heim, Daniel; Brühl, Sonia Patricia
    In this work, the corrosion and mechanical behavior, so as the adhesion of DLC coatings are studied.
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    Propiedades tribológicas y mecánicas de los recubrimientos en base carbono tipo DLC
    (2017-08-17) Delfin, Francisco Andrés; Brühl, Sonia Patricia; Forsich, Christian
    Los recubrimientos hidrogenados en base crbono tipo DLC (Diamond Like Carbon), son depositados sobre diferentes aceros y resultan atractivos por su excelente comportamiento tribológico, bajo coeficiente de fricción, alta dureza superficial y buena resistencia al desgaste, son químicamente inertes y resistentes a la corrosión. Se obtienen mediante técnicas PACVD, que permite depositar recubrimientos finos con alta dureza o bien recubrimientos gruesos pero no tan duros. Debido a que la capacidad de carga aumenta con el espesor, los recubrimientos gruesos pueden ser depositados en aceros más blandos. Con el agregado de silicio disminuyen las tensiones intrínsecas, permitiendo depositar capas de mayor espesor. La superficie del recubrimiento presenta defectos que pueden comprometer su integridad, principalmente cuando estos son pasantes hasta el sustrato, ya que en casos de corrosión pueden ocasionar el desprendimiento de la película. En el presente trabajo se depositaron recubrimientos de varios espesores, a diferentes temperaturas y variando el contenido de silicio. Se observó una incidencia de la posición de las muestras en el interior del reactor en la cantidad y geometría de los defectos, además de una relación directa entre la cantidad de defectos y el espesor del recubrimiento y una relación inversa con la temperatura. Se analizaron los films mediante microscopía óptica y electrónica, topografia conperfilómetro 3D desde la superficie y en la sección transversal, los resultados de Scratch Test revelaron una mejor carga crítica con el incremento del espesor del recubimiento. Fueron obtenidos recubrimientos con un coeficiente de fricción menor a 0.05. Se realizaron ensayos de adhesión por indenación Rockwell C, donde se observó que un aumento en la temperatura resulta en mayor tenacidad a la fractura del recubrimiento.
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    Carbon based DLC films : influence of the processing parameters on the structure and properties
    (2018-07-19) Delfin, Francisco Andrés; Brühl, Sonia Patricia; Forsich, Christian; Heim, Daniel
    Hydrogenated carbon-based films, such as DLC (“Diamond Like Carbon”), have interesting properties such as excellent tribological behavior, low friction coefficient, high superficial hardness and good wear resistance; they are chemically inert and highly corrosion resistant. They are deposited by means of PACVD (plasma-assisted chemical vapor deposition) with variable film thickness. The load carrying capacity grows with the thickness, so it is possible to deposit thick films on “soft” steels (e.g. low alloyed steels). When increasing coating thickness, surface defects are generated during the deposition process compromising their excellent properties. In this work, different metal substrates have been used to compare adhesion and quantify superficial defects: AISI 316L, DIN 42CrMo4 (AISI 4140) and Böhler K110 (AISI D2). The films were deposited at different temperatures, changing the silicon content and the coating thickness. The samples were placed in the furnace on different positions (standing, lying or up-side down). The films were analyzed with optical and electron microscopy, 3D topography profilometer, and they were tested under sliding wear conditions. Friction coefficient and wear volume were measured, with an average friction coefficient which resulted below 0.05. A higher amount of surface defects was obtained on lying samples compared to the ones up-side down. The quantity of defects increased with the thickness of the coating and decreased with the temperature. The geometry and the growth mechanism of the defects were analyzed.
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    Soft and thick DLC deposited on AISI 316L stainless steel with nitriding as pre-treatment tested in severe wear conditions
    (2020) Dalibón Bähler, Eugenia Laura; Moreira, Ramiro Damián; Heim, Daniel; Forsich, Christian; Brühl, Sonia Patricia
    Thick and soft DLC coatings were deposited over stainless steel to improve their surface properties, protecting them from wear in different conditions. When a protective film is thick, it can be considered as self­sustaining in terms of load­carrying capacity during wear situations even if the substrate is soft or hard. Thin and hard DLC coatings are well known for having high hardness and low friction coefficient; however they have adhesion problems when deposited on soft steels and many of their wear properties also depend on adhesion. For this reason, a previous plasma nitriding process may be convenient. In this work, the fretting and erosion wear behaviour of DLC soft coatings deposited on nitrided and non­nitrided austenitic stainless steel was evaluated using high loads and long tests both simulating severe conditions wear. The aim is to analyse under which conditions the film thickness is not enough to withstand wear damage when deposited onto soft steels. The results showed that in the fretting tests, the duplex sample presented better resistance than the only coated sample in all tested conditions, except for the minimum load, 12 N. In slurry erosion tests, the mass loss was similar in both samples until nine hours, when the influence of the nitrided layer became noticeable as a hard layer since the coating partially removed.