Browsing by Author "Tuckart, Walter Roberto"

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    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 Patricia
    A 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.
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    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 Roberto
    Camshafts 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.
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    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 Patricia
    Martensitic 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.