Facultad Regional Concep. del Uruguay
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Item Plasma nitriding plus oxidizing as a protective treatment for AISI 4140 steel(2022-09-29) Dalibón Bähler, Eugenia Laura; Vergniaud, Pablo Martín; Karges, Esteban; Cabo, Amado; Brühl, Sonia PatriciaAISI 4140 is a typical chromium molybdenum medium alloy steel, widely used as construction steel for machine components. Plasma nitriding has been applied as surface hardening treatment with success but the nitrided layer isn ́t always good for corrosion. Plasma nitriding plus oxidizing is proposed as an environmentally friendly alternative which can assure a good wear resistance and also provide a corrosion protective surface layer. In this investigation, heat treated AISI 4140 steel was plasma nitrided in a 15 hours process at 500 C and then oxidized in the same chamber using two different temperatures: 400 C and 500 C, 1 hour duration in a water steam atmosphere. Microstructure was analysed by optical and electronic microscopy and XRD. Wear resistance was tested in a pin on disk machine using alumina as counterpart and corrosion resistance was evaluated in salt spray fog tests and electrochemical tests in NaCl solution, comparing with only nitrided samples of the same steel. The oxide layer was 0.5 microns width, and the nitrided compound layer beneath, 3 microns width. XRD revealed the presence of magnetite and in a minor proportion, hematite in the oxide layer, and gamma iron nitrides in the nitrided layer. In the pin on disk tests with 3 N load no significative variations occurred between the oxidized samples compared with the only nitrided ones, neither in volume loss nor in friction coefficient. On the other hand, in the salt spray fog tests, only the nitrided samples oxidized at 400 C did not present signs of general corrosion after 100 h test. In the electrochemical tests, both oxidized samples had a nobler corrosion potential and a pseudo passive region, showing a better corrosion behaviour of the oxidized samples compared to the nitrided ones, which suffered from active dissolution in the chloride solution.Item Wear resistance of an Hyperlox Gold® coating over nitrided martensitic AISI 420 stainless steel(2022-09-15) Dalibón Bähler, Eugenia Laura; Schierloh, Gonzalo José; Tuckart, Walter Roberto; Brühl, Sonia PatriciaMartensitic stainless AISI 420 steel was plasma nitrided and then coated with an Hyperlox Gold® coating (Cemecon), using the PVD magnetron sputtering technique in an industrial facility at Coating.Tech, Argentina. The coating is mainly AlTiN, covered with a thin layer of TiN to provide the gold colour. Duplex samples (nitrided + coated) were tested in wear comparing with only coated AISI 420 steel and with only nitrided steel. XRD, Nanoindentation, Raman, optical, electronic and confocal microscopy were used to observe the cross section and analyse the wear scars. Adhesion was studied in a Scratch Test following ASTM C1624 standard. Abrasive wear tests were conducted in a sand rubber wheel test (ASTM G65) and adhesive wear tests, in a rotational pin on disk machine using a 6 mm alumina ball as counterpart, and 500 m wear distance using three different normal loads. Steel samples were heat treated to acquire the martensitic structure and 580 HV hardness previous to the plasma nitriding process which was carried out in an industrial facility at IONAR, Argentina in a DC pulsed 10 h process at 390ºC with 20% N2-H2 atmosphere. The nitrided layer was 10 um thick, and the hardness was measured as 1180 ± 40 HV. The Hyperlox coating was about 3 um thick and the TiN top coating 0.5 um thick. Adhesion was good in all cases, but it was better in the duplex sample where 90 N was the critical load, meanwhile in the only coated sample, it was 60 N. In the abrasive wear test, both coated samples showed indetectable wear volume loss in a severe wear test with 130 N load. However, in the adhesive wear test carried out with a pin on disk results were unexpected. With a low load (5 N), the nitrided samples had a better behaviour than the coated samples. At higher loads, 7 N and 10 N, the behaviour was inverse. Moreover, the duplex coated samples lost less volume at 10 N, more at 7 N and even more at 5 N. The discussion will show the influence of surface oxidation in the nitrided steel at low loads to diminish the friction coefficient and how the structural stability of the coating system and the trapped debris determines the wear behaviour in the coated samples. The stress distribution with depth is also considered.Item Duplex treatment - plasma nitriding plus TiAlN coating - to protect martensitic stainless steel from severe wear and corrosion(2022-08-15) Dalibón Bähler, Eugenia Laura; Tuckart, Walter Roberto; Brühl, Sonia PatriciaA combination of plasma nitriding and Hyperlox Gold® coating was designed to Protect AISI 420 martensitic stainless steel against adhesive wear with high contact loads and abrasion. Both surface treatments were carried out in industrial facilities in Argentina and analysed and tested in laboratory. Plasma nitriding was carried out at 390 C in IONAR S.A., with certain parameters to assure not only hardness but corrosion resistance as well. The Hyperlox coating, mainly TiAlN was developed by Cemecon but deposited in Coating.Tech, Argentina, with a TiN coating on top, so is called Hyperlox Gold ®. The coating and nitrided layer were characterized by optical and electronic microscopy, XRD and nanoindentation. Wear tests were carried out in a pin-on-disk machine designed following ASTM G99 standard and abrasion, following ASTM G65. Confocal microscopy, SEM and Raman Spectroscopy were used to analyse wear scars and mechanisms. Adhesion was assessed by Scratch Test and Rockwell C indentation. Corrosion was analyzed in Salty Spray Fog and potentiodynamic tests. The nitrided layer resulted 10 mm width, even though the hardness penetration was deeper. Surface hardness reached 1180 HV. The whole coating was about 3.5 mm thick and adhesion was outstanding, 90 N Lc in the scratch test and HF1 in the RC indentation according VDI 3198. Corrosion resistance was improved in both tests regarding the plain steel and the nitrided steel. In the abrasive wear test, using 130 N load, the wear volume loss was indetectable in the duplex coated samples. However, in the adhesive wear test changing loads, unexpected results have arisen. The duplex coated samples lost less volume at 10 N, but at lower loads, 7 N and 5 N, it lost more. The discussion will show that the trapped debris, the stress distribution in depth and the structural properties of the system determined the wear behaviour.Item Plasma surface engineering to enhance wear and corrosion resistance of stainless steels(2014-11-11) Brühl, Sonia PatriciaA brief description of the research lines of the Surface Engineering Group of UTN will be presented, as well as some important results obtained in the last years concerning plasma nitriding of austenitic stainless steel and different DLC carbon coatings deposited over nitrided martensitic stainless steels.Item Plasma nitriding and plasma nitrocarburizing of a low alloy steel selected to produce camshafts for diesel engines(2015-05-14) Cabo, Amado; Brühl, Sonia Patricia; Prieto, Germán; Tuckart, Walter RobertoCamshafts are a relevant part of diesel engines of extended use today. These components work under torsion and are also prone to fatigue and wear damage. Usually they are manufactured by casting, forging or machining from forged bars of low alloy steels. In most cases, the machined surfaces are quenched and tempered by induction heating. To withstand the efforts imposed on the active surfaces and improve tribological and fatigue properties, the industry used for decades thermochemical technologies such as: salt bath or gaseous nitriding and nitrocarburizing processes. This work studied the effects of plasma nitriding and plasma nitrocarburizing, on the tribological behavior of the steel SAE 1045HM3 proposed to produce camshafts. Results show that plasma nitrided samples present the best tribological behavior compared to the nitrocarburized and quenched and tempered ones. The influence of the roughness produced by the thermochemical processes also appears to be important.Item 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, ChristianThick 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.Item Corrosion resistance of AISI 316L stainless steel nitrided by three different plasma assisted techniques(2014-07-23) Manova, Darina; Mändl, Stephan; Brühl, Sonia Patricia; Escalada, Lisandro; Simison, SilviaPlasma assisted surface modification methods have been used to nitride stainless steels in order to enhance and therefore the lifetime of industrial components. Nevertheless, the corrosion resistance is not always preserved since it is very sensitive to the process parameters, either in implantation or in thermochemical diffusion techniques. AISI 316L stainless steel was plasma nitrided using three different techniques: low energy ion implantation (LEII), plasma immersion implantation (PI3) and convencional DC pulsed plasma nitriding (DCPN). For each method sveral parameters were tested and some of them were selectedto achieve the so called S phase of about 3 um thickness and no nitrides precipitation. The nitrided layer was characterized with OM and SEM. Hardness wass assessed on the surface with Vickers indenter and 25 g load. XRD was performed to characterize The S phase and to detect other phases if present and electrochemical corrosion tests were carried out in 3.5% NaCI solution. Although the S phase thickness in the three groups of samples was comparable, hardness was not and neither wasthe corrosion resistance. The PI3 samples were he hardest with the best performance in corrosion experiments, resulting in a higher breakdown potencial and lower currents.Item Comportamiento a la corrosión de un acero endurecible por precipitación nitrurado y recubierto con SiOxNy(2013-08) Dalibón Bähler, Eugenia Laura; Moscatelli, Mauro Nicolás; Simison, Silvia; Escalada, Lisandro; Cabo, Amado; Lasorsa, Carlos; Brühl, Sonia PatriciaLos aceros inoxidables endurecibles por precipitación (PH) son utilizados en aplicaciones donde se requiere resistencia al desgaste y a la corrosión. Para mejorar las propiedades superficiales se pueden combinar tratamientos termoquímicos con la deposición de un recubrimiento duro. Se presentan los resultados del estudio del comportamiento a la corrosión y a la erosión de un recubrimiento de SiOxNy depositado sobre un acero PH nitrurado (proceso dúplex) comparándolo con el acero sólo nitrurado en dos condiciones diferentes. Se analizó la microestructura, se realizaron ensayos de erosión-corrosión, de corrosión en niebla salina y de polarización cíclica en NaCl. El recubrimiento fue de 1,4 µm de espesor y dureza de 2300 HV. En los ensayos de erosión y de corrosión, el mejor comportamiento lo tuvo la muestra dúplex (nitrurada y recubierta).Esto podría atribuirse a que la capa nitrurada resulta una buena interfaz que mejora la adhesión y aporta un buen soporte mecánico.Item Laser texturing combined with plasma nitriding as a tool to control the tribological performance of steel components(2018-09-28) Lasagni, Andrés Fabián; Dalibón Bähler, Eugenia Laura; Tabares, Ignacio Javier; Aguilar, Alfredo; Brühl, Sonia PatriciaIn this work the sequential combination of both plasma nitriding and laser patterning is analyzed comparing to individual treatments over the same material.Item Development of a post oxidizing process over nitrided medium alloy steels for wear and corrosion protection in oil sucker rod lift(2018-09-28) Cirimello, Pablo; Brühl, Sonia Patricia; Dalibón Bähler, Eugenia Laura; Cabo, Amado; Carfi, Guillermo Rodolfo; Aguirre, Luis AlbertoTo study this surface treatment, AISI 4140 polished PPD prototypes were nitrided, in a DC Plasma industrial equipment, and then were oxidized in the same chamber. Witness specimens were also treated and analyzed in the laboratory.