FRCU - GIS: Grupo de Ingeniería de Superficies - Artículos

Permanent URI for this collectionhttp://48.217.138.120/handle/20.500.12272/812

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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.