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The present study aims to determine the effect of Al on the corrosion resistance of nanostructured TiAlN coatings deposited using a pulsed direct current plasma-assisted chemical vapor deposition (pulsed-DC PACVD) technique. The nanostructured TiAlN coatings were synthesized with three different Al-content values of by distinct precursor’s ratio of AlCl3-to-TiCl4. The number of AlCl3-to-TiCl4 precursor ratios was changed from 1 to 3 in order to vary the Al content. FE-SEM, XRD, EPMA and a Knoop micro-hardness tester were used to characterize the coated surfaces of the specimens. Electrochemical corrosion tests were carried out at 25 ? 1?C to investigate the corrosion behavior of the substrate and the TiN and TiAlN nanostructured coatings
In the present research, the effects of friction stir welding (FSW) on the microstructure of 7075-T6 aluminum alloy (AA) thin sheet were investigated. For this purpose, three different welding rotational speeds of 600, 1000 and 1600?rpm at the constant traverse speed of 50?mm/min were studied. It was observed that FSW of an AA7075 thin sheet leads to an irrecoverable drastic reduction in the tensile properties. However, it was proven that for a thin sheet, at different rotational speeds, totally very different mechanisms of microstructural evolution were present within the stir zone (SZ). Also, it was observed that the mean grain size and subgrain density of the SZ have a nonlinear relation with rotational speed. Electron backscattered dif
This paper investigates the influence of collision angle on the interface characteristics and mechanical properties of magnetic pulse welded AA4014 tubes/Cu rods. It is shown that the collision angle, which affects the collision velocity, plays a crucial role in controlling the thickness of intermetallic compounds (IMC) layer and defect formation at the weld interface. The creation of a thin and continuous IMC layer at the weld interface is responsible for the higher load-bearing capacity of the sample welded under a collision angle of 4?. The welds made at higher collision angles are featured by a thick IMC layer containing defects such as micro-cracks, pores and cavities, which reduced the load-bearing capacity of the joint.
WC-10Ni powder was deposited on Al, Cu, and low carbon steel substrates by cold gas spray method under the process gas pressure of 15 and 35?bar. The effect of substrate on the deposition phenomenon, microstructure, and microhardness of the coatings was evaluated. The cross-section morphology of the coating was studied by the scanning electron microscopy (SEM). The pinning of WC particles caused a high strength between the coating and the substrate. Crack initiation and propagation during cold spraying process, due to the high level of cold working, was the main reason for the high level of porosity of the deposited coating on the Cu substrate. It was found that low carbon steel substrate, for its higher hardness compared to al
The purpose of this study is to produce Zn/ZnO Nanocomposite coatings using cold spray process for sputtering targets applications. Nanocomposite powders were synthesized with different weight percentages of 25, 50 and 75 of ZnO nanoparticles using mechanical milling process. The feedstock was sprayed on pure copper substrates using nitrogen gas at a constant temperature of 150 C, pressure of 15 bar and the stand-off distance of 35 mm. The morphology of composite powders was studied using transmiton electron microscopy; and the wear surface, microstructure and wear debris were studied using scanning electron microscopy. The effect of different values of ZnO nanoparticles on the wear behavior, adhesion strength and surface roughness of the c
Magnetic Pulse Welding (MPW) is an essential procedure for joining of dissimilar metals. The high velocity collision and jetting are the most important aspects of MPW controlled by welding parameters: discharge voltage and air gap. In this study, the collision surfaces and interface of MPW of pure Al and Cu are investigated. The effect of air gap on the bonding is studied by variation of the air gap from 0.7 to 4 mm. The collision surfaces of Cu and Al, the interface of welding and fracture surface were examined by optical microscope and SEM equipped with EDS analysis. The results revealed that the metallurgical bonding is obtained in the air gap of 0.7 mm, whereas higher air gaps (1 to 4 mm) result in debonding due to higher impact e
Magnetic pulse welding (MPW) is a solid-state welding method in which the magnetic forces are used to weld sheets together. The main aim of this paper is to investigate the welding quality of magnetic pulse welded Al/Al and Cu/Cu joints as well as the effect of back-plate support on them. The microstructural examinations by optical and scanning electron microscopes showed that a good bonding is obtained between the sheets welded by the high-velocity impact collision. Depending on the type of back-plate support, the welding interfaces were in either the planar or the wavy form. The microhardness test on the interface exhibited that the back-plate support is much more effective for thinner sheets of metals. It was also observed t
Scale-up deposition methods in perovskite solar cell research, are mostly used under humidity environment outside the glove-box. Also, the as-printed absorbing layer before the post-annealing process is always wet. Thus, controlling the morphology and crystallization of perovskite thin-films in up-scaled deposition systems is difficult and strongly investigated by the researchers. In this work, we introduce an anti-solvent-free meniscus printing method in which, the absorbing perovskite film with optimal performance is achieved. To this end, we check the printing parameters to get to the optimized film characteristics. Also, a vacuum chamber (<100 Pa) is used for 30 s to remove the solvent with appropriate pace from the as-printed wet p
The poor adhesion of nitride coatings to steel substrates is one of the main challenges for industrial applications. In this study, plasma nitriding process and TiN functional intermediate layer were used in order to increase the adhesion of TiCN coating to the hot worked steel H13 substrate and also to improve its mechanical properties. The functionally graded nanostructured TiCN coating was deposited using pulsed-DC plasma-assisted chemical vapor deposition (PACVD) method. The coatings microstructural and mechanical properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), optical microscopy (OM), Rockwell-C indentation, micro hardness and ball-on-disk tests. The results showed that peaks of TiN and T
The present study aimed to join AA4014 to AA7075 by using magnetic pulse welding (MPW). In addition, acceptable joints were achieved by selecting welding parameters such as collision angle and discharge energy appropriately. Changing collision angle and discharge energy can influence the velocity, leading to the formation of three different types of welding interfaces with wavy, molten wavy and porous morphologies. The formation of these various morphologies is mainly associated with different collision angle parameters. The hardness of the welding interface with molten layer was significantly higher than that of the base metals due to the grain refinement phenomenon occurring through the rapid melting and solidification during MPW process.
Stellite alloys are of great interest in industries due to a unique combination of high temperature mechanical strength, outstanding wear and corrosion resistance. Different thermal spraying processes are used for deposition of Stellite alloys on industrial components. However, the investigations on the structure–property relationship of these alloys produced via different deposition process are limited. This study focuses on the microstructure, oxidation, and tribo-mechanical properties of Stellite 21 deposited by cold gas spraying (CGS) and high velocity oxy-fuel (HVOF) process on a low carbon steel substrate. The coating cross-section was characterized by SEM and optical microscopy. The coatings were further characterized by using nano
Cold spraying of Stellite 21 powder on low carbon steel is performed to investigate the effect of traverse speed on the deposition efficiency (DE) of high-temperature alloys. Based on the simulation of particles' impact temperature and velocity, the initial experiments are performed at different gas pressures (32 and 40 bar), temperatures (800 and 730 ?C), and stand-off distances (10, 25, and 40 mm) at a constant traverse speed of 20 mm?s−1. The experiments showed that high pressure, temperature, and short stand-off distance are preferred. The wipe test results indicated a potential of high DE at lower deposition flux over the substrate surface area at the first layer deposition. Thus, new tests are carried out at different traver
In this study, TiSiCN coatings, with and without a Ti/TiN/TiCN interlayer, are deposited on tempered and plasma-nitrided H13 hot-working tool steel substrate by pulsed direct current plasma enhanced chemical vapor deposition. The self-lubricant super hard TiSiCN coatings have a nanocomposite structure consisting of an amorphous SiCN matrix embedding TiCN nanocrystals. In the presence of the graded interlayer, coating adhesion improves significantly, as revealed by a 40% increase of the critical load for adhesion failure in scratch testing of the coated samples. The formation of shorter radial cracks around the indentation zone during Rockwell C indentation test reveals that the coating with the graded interlayer has a higher toughness compa
Hot cracking sensitivity of AA2024-T351 in the electron beam welding (EBW) was evaluated and the effects of welding speeds and heat input on the hot cracking were investigated. In this research, welding speed was set to 15–40 mm/s and microstructure of the welded zone was studied thoroughly by scanning electron microscopy (SEM). Appearance and geometry of weldments were also observed by stereo microscope. Microstructural observations showed that the hot crack length decreased with the increasing welding speed and decreasing the heat input and, as a result, in welding speed of 30 mm/s and heat input of 150 J/mm the crack-free weldment was achieved. The relationship between the welding speed and microstructure of the welded zone was a
Scalable coating methods have recently emerged as practical alternative deposition techniques to the conventional spin-coating despite their lower yielding power conversion efficiencies (PCEs). The most important barrier acting against the use of scalable deposition methods to get a highly absorbing (>95%) film with controlled morphology in the high crystallinity of perovskite particles is the impossibility of antisolvent dripping during the deposition. Here, we demonstrate the positive role of both the surfactant-engineering and the vacuum-annealing (<100 Pa) process in improving the device performance to overcome this limit. A detailed optimization of the vacuum-assisted meniscus printing parameters is discussed to get a pinhole-free trip
The present study investigates the influence of different welding parameters of welding and rotational speeds on the microstructure and the texture in the stir zone (SZ) during friction stir welding (FSW) of a SAF 2205 duplex stainless steel. The FSW process was conducted using a WC– based tool with welding speeds ranging 50–350 mm/min and rotational speeds ranging 400–800 rpm. Microstructure characterization and textural studies showed that fine and dynamically recrystallized grains developed through the microstructure of the SZs and the grain size of the developed microstructures in the SZs is decreased with increasing the welding speed and/or with decreasing the rotational speeds. The intensity of the resultant simple shear tex
In this study, Al-Al2O3 composite coating produced by cold spray method on Al-7075-T6 sheet. The pure Al powder is blended with different amount of Al2O3 powder including 25, 50 and 75 wt. %. The feedstock is sprayed on sand blasted substrate using nitrogen gas at a constant temperature of 300 ?C, pressure of 30 bar and the stand-off distance of 20 mm. The effect of different values of Al2O3 on the deposition behavior of the Al-Al2O3 powders are investigated. Microstructural characteristics of the coatings are evaluated by scanning electron microscopy, image analysis software, microhardness and X-ray diffraction tests. The results showed that the high velocity of particles leads to the Al2O3 particle breaking during the process. This phenom
With the development of the applications of magnesium components in many industries, relatively low corrosion and wear resistance of this alloy leads to the development of different protective layers. In this paper, the effect of SiC reinforcement on the cold spraying behavior of Al-SiC powder on a magnesium alloy substrate is addressed. The pure Al powder is blended with different amount of SiC powder including 25, 50 and 75 wt.%. The feedstock is sprayed on sand blasted AZ31B substrate. The process is carried out with 30bar pressure and 300?C temperature of process gas (Nitrogen). A 20mm standoff distance is used for spraying. The effect of different values of SiC on the deposition behavior of the Al-SiC powders are investigated. The coat
The properties of cold-sprayed ceramic coatings depend not only on the process parameters but also on the feedstock powder characteristics. To clarify the effect of feedstock powder on cold spraying, two titanium oxide powders were used in this study: (1) nanopowder and (2) agglomerated powder prepared with nanoparticles and polyvinyl alcohol. The cross sections of the deposited coatings were observed by scanning electron microscopy (SEM). The results showed that the agglomerated powder with micrometer particles made of nano-sized particles passes successfully through the bow shock layer and reached the substrate, thus forming a coating. These particles are embedded into the substrate and form a strong interfacial coating/sub