The present work was dedicated to study the microstructural, mechanical, tribological and electrochemical properties of the 304L stainless steel multilayer coating formed from four successive layers ...obtained by twin-wire arc spraying and post-annealed with different temperatures. Microstructural results showed that the transformations of the surface aspects from a coating formed of the typical splats features into dot-like shapes morphologies after annealing at 800 °C and to dense flakes and needle-like shapes morphologies at 1000 °C and 1100 °C were taking place. Roughness analysis revealed that the coating annealed at 1100 °C exhibits a very smooth surface. Mechanical analysis showed that with increasing the annealing temperature, the hardness decreases. Tribological analysis results revealed that the coating annealed at 1100 °C possess a low friction coefficient for a stainless steel coating, while for the wear resistance, it decreases with increasing the annealing temperatures which correlated well with the hardness results. The electrochemical results showed that all the four coating has a very interesting corrosion rate, while the coating annealed at 800 °C presents the lowest thermal sprayed coatings corrosion rate. The application of the present work is devoted to replace the mechanical components manufactured by the expensive massive stainless steels that suffer from the sever wear, friction and corrosion with reduced cost and better surface properties.
Austenite stainless steel coatings were deposited on the surface of carbon steel alloy by the twin-wire arc spray (TWAS) process for future application on ball valves surfaces to improve their ...tribological behavior and corrosion performance. Microstructural analysis showed that the sprayed splats size increases with the coatings layers. The coating hardness followed the same trend and reached a value approaching 14 GPa for the four layer coating. The measured Young’s modulus decreased considerably leading to high value of hardness to modulus ratio H/E, thus indicating a superior wear resistance with increasing the number of layers. Tribological test results revealed that the coatings with three and four layers had the lowest friction coefficient of
µ
~ 0.49. The lowest wear rate of 0.54·10
–4
mm
3
/N·m and a four times higher H/E ratio compared to the individual coating layer, were obtained for the coating with four layers. Electrochemical tests results showed that the coatings with two and four layers presented a high capability of protecting the substrate with low corrosion rates that are lower by 8 and 6 times respectively than that of the original ball valve material.
Stainless steel coatings are widely used in abrasive and corrosive environments due to their surface properties, and also to their techno-economic impact. Stainless steel coating deposited by ...Twin-Wire Arc Spray (TWAS) and post-annealed at the vacuum conditions presented very interesting mechanical and corrosion properties, while their tribological behavior, i.e. friction and wear resistance needs further improvement. To enhance those properties, Plasma Immersion Ion Implantation (PIII) technique was used to nitride the coating, afterward, the coatings microstructures were surveyed using Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS), X-Ray Diffraction (XRD) and Atomic Force Microscopy (AFM). Mechanical properties of the coatings were investigated through nanoindentation tests. The tribological properties were also evaluated. A comparison of the obtained results revealed that the hardness of the nitrided coatings could reach 16 GPa, representing a 50% increase compared to the non-nitrided stainless steel coatings. The friction coefficient showed to be 3 times lower after PIII nitriding. Moreover, the wear rate was reduced by 2 orders of magnitude.
Duplex treatment consisting of plasma nitriding and tungsten titanium nitride thin film (W-Ti-N) was applied to 304L stainless steel multilayer coatings to enhance their mechanical and tribological ...properties compared to nitrided and the non-nitrided multilayer coatings. The 304L stainless-steel coating was formed by four layers deposited by twin-wire arc spraying (TWAS) and then post-annealed in vacuum conditions. The coating was nitrided using plasma immersion ion implantation (PIII). W-Ti-N thin film was deposited by physical vapour deposition (PVD) magnetron sputtering using a W + 30 wt.% Ti target. Characterization results showed important mechanical and tribological properties for the duplex-treated stainless-steel multilayer coating, reaching a hardness of 22.3 GPa and a low friction coefficient that was about four times lower than that of the stainless-steel multilayer. Furthermore, the wear rate was three orders of magnitude lower than that of the multilayer. Nitrided stainless-steel multilayers also combined good performance in terms of hardness, friction coefficient, and wear rate.
Ball valves were subjected to severe working conditions that shortened the service life of their components and required additional costs for their maintenance and renovation. The ball valves were ...mainly made from 304 stainless steels (304 SSs). However, its low hardness and corrosion resistance had limited its use. In this study, 317L and 304L stainless steel coatings (317L SSC and 304L SSC, respectively) with thicknesses of 432 and 434 μm respectively were deposited on carbon steel substrates using the twin-wire arc spray system and were comparatively investigated. The mechanical, tribological, and electrochemical properties of the bulk 304 SS were also investigated. Microstructural analysis was carried out using x-ray diffraction, Raman Spectroscopy, Scanning Electron Microscopy and energy-dispersive x-ray spectroscopy. The surface roughness was characterized using Atomic Force Microscope. Lower porosity and oxides content were obtained for 304L SSC, while smooth surface with lower roughness were observed for 317L SSC. Hardness measurement revealed that 317L SSC had higher hardness than 304L SSC. The tribological characterization results showed that both coatings had excellent friction coefficient and wear resistance. The electrochemical tests were carried out in a 3.5wt.% NaCl solution and their results revealed that 304L SSC had a high corrosion resistance.
During this period of COVID-19 pandemic, the lack of medical equipment (like ventilators) leads to complications arising in the medical field. A low-cost ventilator seems to be an alternative ...substitute to fill the lacking. This paper presents a numerical analysis for predicting the delivered parameters of a low-cost mechanical ventilator. Based on several manufactured mechanical ventilators, two proposed designs are investigated in this study. Fluid-structure interaction (FSI) analysis is used for solving any problems with the first design, and computational fluid dynamic (CFD) analysis with moving boundary is used for solving any issues with the second design. For this purpose, ANSYS Workbench platform is used to solve the set of equations. The results showed that the Ambu-bag-based mechanical ventilator exhibited difficulties in controlling ventilation variables, which certainly will cause serious health problems such as barotrauma. The mechanical ventilator based on piston-cylinder is more satisfactory with regards to delivered parameters to the patient. The ways to obtain pressure control mode (PCM) and volume control mode (VCM) are identified. Finally, the ventilator output is highly affected by inlet flow, length of the cylinder, and piston diameter.
Nanocrystalline Fe
90
Ni
10
alloys were synthesized by mechanical alloying, starting from a powder mixture of elemental Fe and Ni. The phase evolution and magnetic properties were investigated, as a ...function of milling time, using the X-ray diffraction (XRD), the vibrating sample magnetometer (VSM), and the
57
Fe Mössbauer spectroscopy. From XRD results, we concluded the formation, after 13 h of milling, of a disordered phase
α
-Fe(Ni) (bcc). It has been shown that the increase of milling time decreases the crystallites size and increases the microstrains and the lattice parameter. When the crystallites size decreases, the coercive field,
H
c
, decreases first, then increases and finally reaches a constant value of about 26 Oe. During the periode of the alloy formation, the saturation magnetization,
M
s
, increases with decreasing crystallite size and reaches the highest value of 212 emu/g after 27 h of milling, then,
M
s
remains constant up to 48 h of milling. The adjustment of Mössbauer spectra revealed that the fraction of the (bcc)
α
-Fe(Ni) phase increased with milling time. After 13 h of milling, only the (bcc)
α
-Fe(Ni) phase is observed.
This paper presents a numerical study of Double-Diffusive convection within an inclined porous medium saturated by a non-Newtonian fluid. The power-law model is utilized for modelling the behavior of ...the flow in the porous layer. The given statement implies that the long side of the cavity experience thermal and solutal flux rates, whereas the other walls are impermeable and thermally isolated. The issue is characterized by a set of tightly linked non-linear differential equations, termed governing equations, encompassing the mass conservation equation (known as the continuity equation), the momentum equation, the energy equation, and the species equation. The relevant factors that govern the problem being investigated are the Rayleigh number, R_T, the power-law index, n, the angle of inclination, Φ, the cavity aspect ratio, A, the Lewis number, Le, the normalized porosity, ξ, and the buoyancy ratio, N, two types of cavity configuration have been studied: inclined cavity (i.e. Φ≠0°), then we have studied the case of a vertical cavity (i.e. Φ=90°) where the buoyancy forces induced by the thermal and solutal effects are opposing each other and of equal intensity (N=-1). A semi-analytical solution, valid for an infinite layer (A>>1), is derived on the basis of the parallel flow approximation, A numerical approach utilizing the finite differences method was utilized to resolve the governing equations within the porous medium. It is demonstrated that both the inclination of the layer, Φ, and the power-law index, n, have a strong influence on the strength of the intensity of flow, Ψ_0, the heat transfer rate, Nu, and the mass transfer rate, Sh, within the enclosure. A good agreement is found between the predictions of the parallel flow approximation and the numerical results obtained by solving the full governing equations.
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