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See detailOxidative wear behaviour of laser clad high speed steel thick deposits: influence of sliding speed, carbide type and morphology
Hashemi, Seyedeh Neda ULg; Mertens, Anne ULg; Montrieux, Henri-Michel ULg et al

in Surface & Coatings Technology (2017), 315

The oxidative wear behaviour of four different High Speed Steel (HSS) thick coatings (one cast material and three laser clad deposits with varying Mo, V and W contents) was investigated using a pin-on ... [more ▼]

The oxidative wear behaviour of four different High Speed Steel (HSS) thick coatings (one cast material and three laser clad deposits with varying Mo, V and W contents) was investigated using a pin-on-disc tribometer at two different sliding speeds of 10cm/s and 50cm/s. Microstructural characterisation (before and after the wear tests) was carried out by SEM and wear debris was analysed by XRD. For all four materials, the oxide layer was formed of hard and brittle haematite-type α-Fe2O3, prone to break and release debris that acted as a third body, thus increasing sample wear. The laser clad HSS materials exhibited a higher wear resistance than their conventional cast counterpart, thanks to their finer microstructures. In particular, the coarser MC and M2C carbides present in the cast material were sensitive to cracking during the wear tests, releasing debris that contributed to increased third body abrasion together with oxide fragments. A detailed comparison of the wear behaviour of the three laser clad deposits, in correlation with their different microstructures, further demonstrated that harder V-rich MC carbides offered better wear resistance compared to the softer W-rich M2C carbides. The morphology of the carbides also played a role in determining the wear resistance at the higher sliding speed of 50 cm/s. Clover-shaped primary MC carbides resisted wear better than angular ones due to their better geometric anchoring. Similarly, the geometric anchoring of eutectic M2C carbides, forming a quasi-continuous network at the grain boundaries of the matrix, proved beneficial at higher sliding speed. [less ▲]

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See detailStudy of the effect of a silver nanoparticle seeding layer on the crystallisation temperature, photoinduced hydrophylic and catalytic properties of TiO 2 thin films deposited on glass by magnetron sputtering
Limage, H.; Tichelaar, F. D.; Closset, Raphaël ULg et al

in Surface & Coatings Technology (2011), 205(13-14), 3774-3778

The optimization of the photocatalytic activity and hydrophilic conversion of TiO 2 is an active research area in the field of self-cleaning materials and energy storage/conversion. One major focus is the ... [more ▼]

The optimization of the photocatalytic activity and hydrophilic conversion of TiO 2 is an active research area in the field of self-cleaning materials and energy storage/conversion. One major focus is the crystalline phase of TiO 2, known to be the most efficient of the anatase structures. Another issue is the decoration of TiO 2 with noble metals, which act as charge carrier traps for electrons. The latter hinders or reduces the electron-hole recombination rate and often leads to a more efficient photocatalytic activity. In this paper, we describe how an interlayer consisting of 3-4nm silver nanoparticles (Ag-NPs) promotes TiO 2 anatase crystallisation and has a positive effect on the photoinduced catalytic and hydrophylic properties of TiO 2 thin films. Ag-NPs and TiO 2 were deposited by magnetron sputtering in the same reactor in a two-step process: a) condensation of Ag-NPs produced in the gas phase thanks to a high-pressure discharge, and b) conventional TiO 2 magnetron deposition in oxide mode. Four temperatures from RT to 288°C were investigated and film thickness was 80nm. Particle size and film structure were determined by TEM, HRTEM and XRD. Photocatalytic activities of the samples were tracked by the evaluation of the surface hydrophilicity after UV illumination and 24. hours post-illumination, and by UV-induced palmitic acid degradation. © 2011. [less ▲]

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See detailMechanical properties of Al/Al2O3 nanolaminated films: correlation to microstructure
Ben Daia, M.; Aubert, P.; Labdi, S. et al

in Surface & Coatings Technology (2000), 125(1-3), 196-200

Wear resistance and the hardness of Al/Al2O3 nanolaminated films were investigated in this study. Monolithic films and multilayers were deposited on a silicon substrate with two different substrate ... [more ▼]

Wear resistance and the hardness of Al/Al2O3 nanolaminated films were investigated in this study. Monolithic films and multilayers were deposited on a silicon substrate with two different substrate temperatures: T-s= 25 degrees C and T-s= -90 degrees C. The period thickness of multilayers was lowering from 40 to 2 nm. From nanoindentation measurements, it appears that the hardness of multilayers has an intermediate value between those of metal (Al) and ceramic (Al2O3). The tribological test was conducted by the pin-on-disc method. The T-s=25 degrees C deposited multilayers, as well as single films, demonstrated poor wear resistance. The best wear resistance was obtained for multilayers deposited at the lowest substrate temperature (T-s= -90 degrees C). The results are ill good agreement with structural characterization. X-ray reflectometry demonstrated that the multilayer character of Al/Al2O3 is more pronounced for T-s= -90 degrees C. (C) 2000 Elsevier Science S.A. All rights reserved. [less ▲]

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