Magnetron sputtering is one of the most commonly used deposition techniques, which has received considerable attention in industrial applications. In particular, owing to its compatibility with ...conventional fabrication processes, it can produce and fabricate high-quality dense thin films of a wide range of materials. In the present study, nitrogen (N) was combined with pure vanadium in order to form binary nitride to improve its mechanical and tribological performance. To evaluate the influence of nitrogen on the structure of the as-deposited vanadium nitride (VN) coatings, the following techniques were used: XPS, XRD, SEM, AFM and optical profilometry. The residual stresses were determined by the curvature method using Stoney’s formula. The hardness and Young’s modulus were obtained by nanoindentation measurements. The friction behavior and wear characteristics of the films were evaluated by using a ball-on-disk tribometer. The obtained results showed that the N/V ratio increased with increasing the N
2
flow rate while the deposition rate decreased. The preferred orientation was changed from (200) to (111) as the N
2
flow rate increased with the presence of V–N and V–O binding energies as confirmed by XPS analysis. The nitrogen addition resulted in a columnar morphology and a fine structure with fine surface roughness. The VN thin film containing 49.5 at.% of nitrogen showed the best performance: highest mechanical properties (hardness = 25 GPa), lowest friction coefficient (
μ
= 0.37) and lowest wear rate (W
s
= 2.72 × 10
−5
mm
3
N
−1
m
−1
). A good correlation between the film microstructure, crystallite size, residual stress and mechanical and tribological properties was observed.
Chromium nitrides were deposited by RF reactive magnetron sputtering from a Cr target on high carbon steel substrates XC100 (1.17 wt% carbon) in a N2 and Ar gas mixture. In order to investigate the ...formation of chromium nitrides, carbide and carbonitride compounds were subjected to vacuum annealing treatment for 1 h at various temperatures ranging from 700 to 1000 °C. The samples were characterized by EDS, XPS, XRD, SEM, nanoindentation and tribometry. The results showed the emergence of Cr2N and CrN during the early stages of annealing and the appearance of chromium carbonitride phases only at 900 °C. The (111) preferred orientation of the fcc CrN phase was changed to (002) at 900 °C in parallel with the appearance of chromium carbides. Nanoindentation tests revealed a gradual increase of the Young's modulus from 198 to 264 GPa when increasing the annealing temperature, while the hardness showed a maximum value (H = 22.4 GPa) at 900 °C. The low friction coefficient of the CrCN coating against a 100Cr6 ball was approximately 0.42 at 900 °C. The enhancement of mechanical and tribological properties was attributed to the stronger bonding CrC at the CrN/XC100 interfaces as confirmed by XPS results.
•CrCN coatings were deposited on steel by RF reactive magnetron sputtering.•Microstructure of the coatings was strongly affected by the annealing treatment.•High temperature promotes the diffusion of carbon from substrate towards the film.•Thermal durability and high abrasive wear resistance with CrC and CrN bonds.
In the plasma ionic environment of nitrogen and hydrogen at 4:1 ratio, nitriding had been realized in the plasma laboratory. Nitriding of steel samples was followed at the lower temperature of 450 °C ...and also at the higher temperature of 550 °C while the sample was biased at the fixed − 250 V. Steel nitrided at 550 °C had shown a significantly enhanced resistance to corrosion in comparison to that of steel nitrided at 450 °C. X-ray diffraction studies of nitrided steels had shown the presence of nitrides of iron (FexN). Scanning electron microscopic and the electron dispersive spectroscopic analyses (SEM + EDS) of the cross section of the nitrided steels had shown the nitrided layer and the elemental distribution from top to the core. Following structural analysis, microhardness and the potentiodynamic polarization tests were performed. A significant improvement in hardness (~ 1180 Hv) and the case depth ~ 150 µm was obtained after nitriding at the higher temperature. Corrosion resistance was also found to be significantly improved. These achievements might be attributed to the presence of FexN, CrN phases and also to the nitrogen solid solution.
This study presents the plasma nitriding of Cr–Mo–V tool steel to protect it from environmental degradation. The steel samples after metallographic polishing were nitrided in the glow discharge ...plasma of N
2
and H
2
gas mixture (80:20). Nitriding was performed at two different temperatures, a lower temperature of 450 °C and the higher temperature of 500 °C. The potentiodynamic polarization tests in 3.5% NaCl electrolyte had shown the enhancement of corrosion resistance of steels after nitriding. X-ray diffraction (XRD) studies and scanning electron microscopic analysis coupled with energy dispersive spectroscopic analysis (SEM/EDS) was performed to understand the modification of surface microstructure. XRD analysis of the nitrided steels revealed the presence of γ′- and ε-nitrides of iron, which were responsible for the improvement of corrosion resistance.
The contact between the tool and the workpiece/chip in metal cutting is complex, resulting in high local temperatures and stresses, which may cause severe tool wear and failure. Developments in ...cryogenic-assisted machining have shown an ecological alternative to the classical metal working fluids, besides tool wear reduction during machining difficult-to-cut materials due to the good ability to dissipate the heat generated by this process. The objective of this work is to analyze the tribological conditions and performance of new coatings specially developed for cryogenic-assisted machining in terms of friction coefficient, volume of build-up material (adhesion) to the tool, and tool temperature. The results have shown that the sliding speed and cooling/lubrication strategy are two main factors that affect the friction coefficient and adhesion of Ti–6Al–4V alloy to the pins. These tribological tests should allow us to select the best coating(s) to be used in cutting tools for further tool wear analysis. Moreover, the obtained friction coefficients could be further implemented into metal cutting models to predict the machining outcomes, including the surface integrity of the machined parts and tool wear.
This study aims to examine the effect of replacing vanadium by niobium and iron on the tribological behavior of hot-isostatic-pressed titanium alloy (Ti–6Al–4V) biomaterial, using a ball-on-disk-type ...oscillating tribometer, under wet conditions using physiological solution in accordance with the ISO7148 standards. The tests were carried out under a normal load of 6 N, with an AISI 52100 grade steel ball as a counter face. The morphological changes and structural evolution of the nanoparticle powders using different milling times (2, 6, 12 and 18 h) were studied. The morphological characterization indicated that the particle and crystallite size continuously decrease with increasing milling time to reach the lowest value of 4 nm at 18-h milling. The friction coefficient and wear rate were lower in the samples milled at 18 h (0.226, 0.297 and 0.423; and 0.66 × 10
−2
, 0.87 × 10
−2
and 1.51 × 10
−2
µm
3
N
−1
µm
−1
) for Ti–6Al–4Fe, Ti–6Al–7Nb and Ti–6Al–4V, respectively. This improvement in friction and wear resistance is attributed to the grain refinement at 18-h milling. The Ti–6Al–4Fe samples showed good tribological performance for all milling times.
The present concerns surface modification of low alloy CrMoV steel by following the route of plasma nitriding for the improvement of hardness. Plasma nitriding was performed at a low temperature of ...450 oC. The maximum hardness at this lower temperature was found to be ∼1270 Hv after nitriding. At 550 oC though the hardness improvement near the surface region was similar but the core hardness was reduced. XRD studies revealed various nitrides of iron (γ′ (Fe4N) and ε (Fe2–3N)) with the ε nitride as the dominant phase. SEM analyses revealed the surface microstructure with almost no white layer. EDS point analyses shown the signature of N on the surface layer. It has been concluded in this study that the hardness of 90CrMoV8 steel can be improved significantly even at a low temperature of 450 oC without any of risk of the loss of core hardness.
Physical vapor deposition (PVD) coatings namely Cr/CrN, Cr/ CrN / CrAlN multilayers (period of μ = 4 with a Cr bonding layer 138 nm thick), have been synthesized on a quenched and tempered X38CrMoV8 ...steel to test their ability to avoid soldering during casting of aluminum alloys. Wear tests, optical profilemetry observations and demolding stress tests were carried out. Intermetallic compounds were formed and aluminum cast alloy soldering layer was found on surfaces of all tested pins, which were observed and quantified by SEM/EDS. Cr/CrN multilayers have been found to exhibit the bestperformance among all materials and coatings considered here. The results showed low friction coefficient of Cr/ CrN multilayers and the amounts of intermetallic compounds were lower than those formed on Cr/CrN/CrAlN ones.
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