Formation Of Oxide Film Research Articles

Influence of layer number and sintering temperature on microstructural, tribological, and corrosion behavior of Al2O3–TiO2 multilayer coatings

The effects of layer number (2, 4, and 6-layer) and sintering temperature (800, 900, 1000, and 1100 °C) on the microstructure, wear, and corrosion properties of Al2O3–TiO2 multilayer coatings deposited on 316L stainless steel plates using the sol-gel dip coating technique were investigated. The wear characteristics were measured through ball-on-disc type dry sliding tests using an Al2O3 ball under a 1 N load, whereas the corrosion features were determined by potentiodynamic polarization tests conducted in a 3.5 wt% NaCl solution. Anatase, rutile, α-Al2O3, and γ-Al2O3 phases were obtained in the hybrid coatings, depending on the sintering temperatures. However, at 1100 °C, the coating did not adhere well to the substrate due to passive oxide film formation on the 316L plate, leading to spalling. Besides, the surface homogeneity deteriorated in the 6-layer coated sample due to higher organic removal and residual stresses. The corrosion rate decreased with the increasing number of layers, but the sensitivity to corrosion varied due to changes in surface properties. The 4-layer coated sample sintered at 1000 °C achieved the highest wear strength (improved by up to 71.1%) and corrosion resistance (increased by up to 90.4%) due to its decreased porosity and homogeneously distributed finer particles.

Tribocorrosion behavior of Co-based self-lubricating composites with varying contents of Ag in NaCl solution

Majority of self-lubricating composites exhibit a high wear rate due to corrosion. In this study, Co-based self-lubricating composites with addition of Ag were prepared via spark plasma sintering to manage their tribocorrosion resistance. No interfacial reaction occurred after sintering. Their tribocorrosion behavior in 3.5 wt.% NaCl solution was characterized as a function of applied potentials. In corrosion-free conditions, i.e. applying a cathodic potential (−1 V), the addition of Ag enhances wear rate of the Co-based composites. While in a state of OCP or applying an anodic potential, galvanic corrosion occurs between Ag and Co-matrix. It promotes the formation of a loose oxide film and reserves most silver debris, which contributes synergistically to reduced friction coefficient and wear rate. With the addition of 12 wt.% Ag, Co-based self-lubricating composite exhibits the lowest friction coefficient of 0.09 and wear rate of 3.8 × 10−5 mm3/(Nm) at OCP.

Electrochemical and surface characterization of anodized and fs-laser treated Ti6Al4V for osseo-repellent bone screws and dental implants

The surfaces of titanium grade 5 (Ti6Al4V) samples were altered on a micro and nano scale by femtosecond laser irradiation and subsequent electrochemical anodization. The produced micro-cones and nano-ripples covered by the additional oxide layer were characterised and their influence on osteoblast-like Saos-2 cell growth was studied. Surface topography and morphology were studied by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). From the wettability experiments, it was found that the contact angle vs. roughness follows the Wenzel equation and that the wettability increases after the anodization. The composition of the formed oxide layer was determined by X-ray photoelectron spectroscopy (XPS) and oxide incorporation of phosphate ions could be confirmed. Moreover, estimated electrochemical surface area (ECSA) of the femtosecond laser treated sample was 14 times larger compared to a polished sample. The anodic oxide film formation factors for different electrolytes were determined and were in the range of 1.3 nm V−1–2.0 nm V−1. Finally, the samples anodized with 0.1 M H2SO4 and 3 M H3PO4 showed decreased Saos-2 cell growth.

Improving corrosion resistance of Mg–Li alloys by Sn microalloying

It is well known that the corrosion resistance of ultra-light Mg–Li alloys is inferior to traditional Mg alloys due to the rapid oxidation of reactive Li on the surface. In this study, microalloying Sn has been found to improve the corrosion resistance of Mg–Li alloys due to the formation of Mg2Sn on the corrosion pits and reduction of electro-potential difference. Indeed, the addition of Sn not only reduced the corrosion rate to the minimum value of 4.27 mmpy but also promote the formation of dense corrosion oxide films. The volt potential difference between the matrix (α-Mg and β-Li) and Al-X (Gd, Y, Mn) phases has also been measured to reduce from 260 mV (α-Mg) and 343 mV (β-Li) to 220 mV (α-Mg) and 220 mV (β-Li). After homogenization, pitting was significantly reduced, as shown by the in-situ observation of the corrosion process using X-ray tomography. By quantifying the secondary phases, it has been found that the corrosion expansion was restricted by the Mg2Sn and Al-X phases. The corrosion products are primarily MgO, SnO, and Li2O oxides and the corrosion mechanism follows three stages: I. Breakthrough of MgO protective layer by corrosive fluid; II. Hydrogen evolution reaction (HER) between matrix phase and water immersion; III. Segregation of secondary phases and corrosion products. It has been found that all three processes are highly dependent on the Sn solutes and Mg2Sn precipitates, showing the bright future development of corrosion-resistant Mg–Li alloys by Sn microalloying.

Direct bonding of Ni nanoparticles to a semiconductor Al electrode in air and its form

This research group evaluated the bondability of sinter bonding using Ni nanoparticles, which have a high melting point and excellent corrosion resistance, as a new metal nanoparticle bonding material, and found that bonding is possible at bonding temperatures below 400 °C when the particle size is less than 100 nm. Furthermore it was found that Ni nanoparticles can be directly bonded to Al, which is considered difficult to bond directly with solder materials containing tin (Sn) or lead (Pb), and that high bonding strength can be obtained. In addition, the bonding strength of Ni nanoparticles to Al was higher when bonded in air than in a reduction atmosphere of N2+H2 (3%), indicating that there were differences in bonding properties depending on the bonding atmosphere. In this study, we compared the bonding properties to Al in different bonding atmospheres. In the N2+H2 (3%) reducing atmosphere, the bonding strength was not increased even when the bonding temperature was increased. On the other hand, the bonding strength was significantly increased with increasing bonding temperature over 330 °C in air. The failure mode was also rupture in the bonding layer, and good bonding was achieved at the Ni/Al bonding interface. Observation of the bonding interface between Ni nanoparticles and Al using Transmission electron microscope (TEM) showed the presence of an interlayer of oxide film at both bonding interfaces in air and in the N2+H2 (3%) reduction atmosphere. And the oxide layer at the interface bonded in air was thicker, indicating that the structure at the interface between the Ni layer, the oxide layer and the Al layer has changed. It was suggested that the difference in oxide film formation behavior, structure, and thickness affects the bondability due to the difference in the bonding atmosphere.

Near substrate surface plasma characteristics of ZnO film deposition in DC reactive magnetron sputtering with water vapor

The effect of varying the water vapor content in a DC magnetron sputtering process was investigated for zinc oxide film formation. The plasma parameters near the substrate surface were measured using a single Langmuir probe, and the deposited films were characterized using X-ray diffraction, X-ray reflectivity, optical transmittance, and 4-point probe methods. In the region near the substrate surface, the addition of water changes the plasma properties, and the measured plasma parameters showed the changes corresponding to the transition in the film growth mechanism from Zn to ZnO. Depositing at 40% water content resulted to a highly transparent film with a ρ of 1.20 Ω cm. The band gap of films deposited at 40%–100% water content ranged from 3.36 to 3.34 eV, which matches the expected shallow hydrogen donor doping in ZnO.

Tailoring the discharge performance of extruded Mg-Sm-Al anode for Mg-air battery applications via control of Al content

We investigated the discharge performance and electrochemical properties of an as-extruded Mg-5Sm-xAl (x = 0,1,3) anode for Mg-air batteries. Adding Al modified the phase composition and grain size of the anode. The addition of 1 wt% Al (Mg-5Sm-1Al) induced a high discharge voltage and power density due to the stimulation of the evenly distributed, fine Al11Sm3 particles. However, these particles increased the parasitical anodic hydrogen reaction rate, resulting in a decrease in anodic efficiency. These properties make the anode suitable for high-power density applications. The addition of 3 wt % Al (Mg-5Sm-3Al) promoted the formation of an aluminium oxide film on the anode surface, which suppressed the anodic hydrogen reaction to improve the anodic efficiency. This film increased the battery's internal resistance resulting in low voltage. This anode is a good candidate for heavy-duty battery applications, where a steady voltage output and long service life are desired. By controlling the Al content, the tailoring of discharge performance of the Mg-Sm-Al anode is feasible to satisfy different battery load requirements.

Investigating the structure of the oxide on Ni‐Cr‐Mo alloys while presenting a method for analysis of complex oxides using QUASES

X‐ray photoelectron spectroscopy (XPS) is a technique that is widely used to study thin oxide films because of its extremely high surface sensitivity. Utilizing the QUASES (Quantitative Analysis of Surfaces by Electron Spectroscopy) software package developed by Sven Tougaard (University of Southern Denmark), a user can obtain additional information that is not extracted in conventional XPS analysis, specifically the composition as a function of depth. Presented here is the QUASES analysis of four Ni‐Cr‐Mo alloys performed while testing various inelastic mean free path (IMFP) determination methods in the context of providing a framework for the analysis of complex oxides in QUASES. Ni‐Cr‐Mo alloys are often used to replace conventional materials under aggressive conditions, because of their exceptional corrosion resistance. Their corrosion resistance is conferred by the formation of an inert surface oxide film that protects the underlying metal. Using the QUASES software, the thickness of the air‐formed oxide on four Ni‐Cr‐Mo alloys was found to lie within the range of 2.5–3.6 nm. They were found to be composed of an inner Cr2O3 layer and an outer Cr (OH)3 layer, with a transition zone where the two coexisted. Oxidized Mo species, MoO2 and MoO3, were found in trace amounts at the boundary between the Cr2O3‐only and mixed Cr2O3/Cr (OH)3 regions of the oxide. We also determined that using 20% reduced IMFP values gave results similar to those obtained using electron effective attenuation length (EAL) values. Auger depth profiles showed comparable trends to the QUASES models.

Interfacial microstructures and corrosion behavior of tungsten heavy alloy/superalloy dissimilar joints: design, regulation and mechanism

The interfacial microstructures and corrosion behavior of tungsten heavy alloy/superalloy dissimilar joints brazed with various Cu–Ti based multicomponent amorphous alloys were investigated by time-varying chemical bath immersion tests and electrochemical measurements. The longitudinal analysis of corrosion behavior differences in different regions of dissimilar joints was conducted, and the horizontal analysis of the influence of compositional variation in filler materials on corrosion behavior was investigated. Importantly, the brazed joint with CuTiNiZrV filler material (CT3 joint) exhibited the noblest Ecorr (−0.911 VSCE) and the highest charge transfer resistance (1610.5 Ω cm2). From the compositional and microstructural effects on the corrosion resistance, the enhancing anti-corrosion performance was mainly attributed to the tailoring of the microstructures and corrosion potential of the brazing seam, and the formation of protective compact oxide film (Fe2O3-NiO-CoO-VO).

A Scalable Method for Enhancing the Crystallinity of Zn Powder to Reduce Corrosion and Boost Achievable Capacity

Zinc corrosion is an unavoidable phenomenon in alkaline systems. Additives like surfactants and metals at the ppm level are typically included in the zinc-alkaline cell production process to help suppress corrosion. Though these inclusions have helped remediate the issue, the inclusions themselves bring forward new issues such as increased toxicity and cost. Therefore, a method for achieving reduced Zn corrosion that can either complement or replace additives is highly desirable. In this work, a method for the scalable improvement of zinc microparticle crystallinity, without the use of additives, is presented and detailed. The recrystallization process involves oxide film formation, thermal annealing, and oxide film removal. The process converts polycrystalline particles into either a single crystal or one with larger, fewer total grains while conserving particle shape and size. This paper demonstrates reduced corrosion and enhanced achievable capacity for the recrystallized particles as well as improved cyclability. More specifically, the recrystallized particles demonstrate a 19% reduction in corrosion current and a 12% increase in achievable capacity when probed by linear sweep voltammetry and constant current discharge, respectively. When cycled in charge-discharge experiments, the recrystallized particles boast up to a 114% improvement in cyclability.

Improving the corrosion resistance of Mg-8Li-3Al-2Zn alloy by combining Gd alloying and hot extrusion

The microstructure and corrosion behavior of Mg-8Li-3Al-2Zn(−1.0Gd) alloys were investigated. In as-homogenized LAZ832(−1.0Gd) alloys, galvanic corrosion occurs at α-Mg/β-Li phase interface, and pitting corrosion occurs in α-Mg matrix and β-Li matrix. After hot extrusion, the corrosion form of α-Mg matrix changes to intergranular corrosion. The corrosion resistance of LAZ832 alloy is effectively improved by combining Gd alloying and hot extrusion, and as-extruded LAZ832–1.0Gd alloy exhibits the best corrosion resistance with a corrosion rate of 0.64 mm·y−1. Gd alloying improves corrosion resistance mainly due to the formation of Al2Gd phase, the reduction of AlLi phase, and the formation of oxide film containing Gd2O3. Hot extrusion improves corrosion resistance mainly attributed to the increase in the share of basal orientation and the crushing of fibrous AlLi phase.

Improved Tribocorrosion Properties of Ti6Al4V Alloy by Anodic Plasma Electrolytic Oxidation

Ti6Al4V alloy has good corrosion resistance due to the formation of the passive oxide films on the surface of Ti6Al4V alloy. However, Ti6Al4V alloy has poor tribocorrosion resistance in the seawater environment. Herein the present work, plasma electrolytic oxidation (PEO) with the electrolyte of glycerol and sodium borate is used to generate PEO coatings on the surface of Ti6Al4V alloy to improve its tribocorrosion properties. The microstructure and tribocorrosion properties of PEO coatings are investigated by using scanning electron microscopy, X‐ray diffraction, and tribometer, respectively. The growth kinetics and the tribocorrosion mechanisms of PEO coatings are discussed in detail. It is shown in the results that PEO coatings deposited on the surface of Ti6Al4V alloy are composed of rutile and anatase phases. The surface hardness and thickness of PEO coatings are enhanced with the increase of the voltage and time. The wear rate of Ti6Al4V alloy with PEO coatings is significantly reduced in artificial seawater.

Effect of Aging Heat Treatment on Wear Behavior and Microstructure Characterization of Newly Developed Al7075+Ti Alloys.

In this study, Al7075+0%Ti-, Al7075+2%Ti-, Al7075+4%Ti-, and Al7075+8%Ti-reinforced alloys were prepared by melting processes using Al7075 and Al-10%Ti main alloys. All newly produced alloys were subjected to T6 aging heat treatment and some samples were cold rolled at 5% beforehand. The microstructure, mechanical behavior, and dry-wear behavior of the new alloys were examined. Dry-wear tests of all alloys were carried out at a total sliding distance of 1000 m, at a sliding speed of 0.1 m/s, and under a load of 20 N. In the hardness measured after T6 aging heat treatment, the peak hardness of the Al7075+0%Ti-, Al7075+2%Ti-, Al7075+4%Ti-, and Al7075+8%Ti-reinforced alloys was found to be 105.63, 113.60, 122.44, and 140.41 HB, respectively. The secondary phases formed by the addition of Ti to the Al7075 alloy acted as precipitate-nucleation sites during aging heat treatment, further increasing the peak hardness. Compared to the peak hardness of the unrolled Al7075+0%Ti alloy, the increase in the peak hardness of the unrolled and rolled Al7075+8%Ti-reinforced alloys was 34% and 47%, respectively, and this difference in the increase was due to the change in the dislocation density with cold deformation. According to the dry-wear test results, the wear resistance of the Al7075 alloy increased by 108.5% with a reinforcement of 8% Ti. This result can be attributed to the formation of Al, Mg, and Ti-based oxide films during wear, as well as the precipitation hardening, the secondary hardening with acicular and spherical Al3Ti phases, the grain refinement, and solid-solution-hardening mechanisms.

Effect of Chromium Oxide Film Formation, Mainly by the INCO Method, on Hydrogen Permeability on Welded Type 304 Stainless Steel

Effect of Chromium Oxide Film Formation, Mainly by the INCO Method, on Hydrogen Permeability on Welded Type 304 Stainless Steel

Corundum-structured AlCrNbTi oxide film grown using high-energy early-arriving ion irradiation in high-power impulse magnetron sputtering

Multicomponent or high-entropy oxide films are of interest due to their remarkable structure and properties. Here, energetic ion irradiation is utilized for controlling the phase formation and structure of AlCrNbTi oxide at growth temperature of 500°C. The ion acceleration is achieved by using a high-power impulse magnetron sputtering (HiPIMS) discharge, accompanied by a 10 μs-long synchronized substrate bias (Usync), to minimize the surface charging effect and accelerate early-arriving ions, mainly Al+, O+, Ar2+, and Al2+. By increasing the magnitude of Usync from −100 V to −500 V, the film structure changes from amorphous to single-phase corundum, followed by the formation of high-number-density stacking faults (or nanotwins) at Usync = −500 V. This approach paves the way to tailor the high-temperature-phase and defect formation of oxide films at low growth temperature, with prospects for use in protective-coating and dielectric applications.

Effect of Y2O3 on the microstructure and tribology property of WMoTaNb refractory high entropy alloy coating prepared by laser cladding

Recently, high-entropy alloys (HEAs) reinforced with ceramic particles have attracted increasing attention due to their excellent hardness and wear resistance. In this study, the WMoTaNb-Y2O3 refractory high-entropy alloy coatings were produced on Inconel 718 by laser cladding to improve the microhardness and high-temperature wear resistance of the substrate. The phase composition, microstructure, and mechanical properties of the HEAs were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), microhardness, and wear resistance tests. The results show that due to the high entropy effect and elemental diffusion, the WMoTaNb-Y2O3 refractory high-entropy alloy coatings comprise simple BCC and Fe-containing phases. Y2O3 particles are mainly distributed at the surface of the high-entropy alloys coatings. Y2O3 particles have an advantage in the inhibition of HEAs grain growth attributed to a strong pinning effect. The microhardness and the wear resistance of the HEA composite improved significantly with the addition of Y2O3 particles. A good comprehensive mechanical properties was obtained at the HEA with the addition of 3 wt% Y2O3 particles, which microhardness can reach to 1274.6 HV0.2. The laser-cladded WMoTaNb-Y2O3 high-entropy alloy coatings show a good wear performance at high temperature, which is mainly attributed to the formation of oxide films on the surface of the coating. The wear mechanisms are dominated by abrasive wear, adhesive wear and oxidative wear. The HEAs coating with 3 wt% Y2O3 has the best tribological performance at 800 °C with the minimum friction coefficient is around 0.4 and the minimum wear rate of only 0.58 × 10−5 mm3/Nm, respectively.

Effect of alloying elements (Mn, Ti, and Mo) on the corrosion behavior of FeCoNiCr-based high entropy alloy in supercritical water

The effect of alloying elements, Mn, Ti, and Mo, on the corrosion behavior of FeCoNiCr-based high entropy alloy (HEA) in supercritical water was investigated. The corrosion resistance of the HEA was enhanced by adding Mo while reduced with the addition of Ti and Mn. The segregation of Ti and Mo resulted in the formation of oxide films that were both structurally and chemically heterogeneous. Grain boundaries accelerated the diffusion rate of Mn, leading to the formation of MnCr2O4 oxide scales decorated with Mn2O3 particles. In addition, the governing mechanisms of alloying elements on the corrosion behavior of HEAs were also discussed.

Sustainable electrochemical gold dissolution process based on triboelectric nanogenerator

The development of sustainable, energy-free dissolution methods is crucial for gold recycling. For the first time, we have achieved the dissolution of gold through a triboelectric nanogenerator (TENG). With 1 wt% Au/SiO2 as the research subject in KI solution, the gold dissolution efficiency can reach 100 % in three hours driven by R-TENG. However, by using a direct current (DC) source with 25 mA and 5 V, the gold dissolution efficiency is only 85 % after the same operation time. Meanwhile, to achieve the same 85 % gold dissolution rate, the total charge consumed from TENG is only 1.6 % of that from the DC source, indicating an ultrahigh charge utilization rate. Thus, the side reactions such as water splitting and the formation of the iodine oxide film in KI aqueous solution can be avoided by using TENG, which blocks the adhesion on the anode and facilitates the reaction. The amount of gold extracted from the waste central processing units (CPU) board (4 × 4 cm) by the solution method could reach 6 mg/piece. Hence, TENGs provide a new direction for the recovery of other metals in secondary resources and many other applications in the direction of electrochemistry can be also inspired.

Revealing and simulating the effect of hidden damage on local and full-field deformation behaviour of cast aluminium

Pores have been the main focus of quality assurance in castings. Latest research has shown that in aluminium castings pores can form only if there is existing entrainment damage, i.e., pores are merely the visible parts of the entrainment damage, and usually invisible damage is much more extensive. However, its effect on deformation behaviour has not been previously established or observed in-situ. This work applies 2D Digital Image Correlation (DIC) to an in-situ full-field stress-strain analysis of tensile samples with a non-conventional heterogeneous stress distribution. The observations reveal that the effect of hidden damage extends far beyond its impact on fracture behaviour and is responsible for initiating local strain concentrations during deformation. By extracting local stress-strain data, FE simulations have been performed to mimic the effect of local hidden damage on the heterogeneous stress-strain field. SEM and FIB-SEM analysis has been applied to investigate the cause for the strain concentrations. The combined results show that hidden damage in the form of oxide films is not only responsible for premature fracture, but also affects the deformation behaviour of tensile samples by introducing dispersed strain concentrations.

INFLUENCE OF STRONTIUM ADDITION ON OXIDATION KINETICS OF INDUSTRIAL CAST ALUMINUM ALLOYS AL2, AL4 AND AL9

When melting cast aluminum alloys, their waste is observed, or more precisely, oxidation by the gas phase of the furnace. To select the optimal regime for melting alloys, it is necessary to know the physicochemical laws of this process, which are little studied. To study the kinetics of oxidation of metal melts, the method of continuous sample weighing is used, which is usually used in the study of high-temperature corrosion of solid metals. The mechanism of interaction of liquid metals with oxygen is similar in nature to high-temperature gas corrosion of solid metals. In both cases, adsorption of gas molecules on the metal surface, nucleation, and then growth of an oxide film take place. The kinetics of oxidation of strontium-modified AL2, AL4, and AL9 melts with atmospheric oxygen was studied by thermogravimetry. It is shown that the addition of strontium up to 0.1 wt % increases the oxidizability of melts. An increase in temperature promotes an increase in the rate of oxidation of these melts. The process of oxidation of the investigated melts obeys the parabolic law. The true rate of oxidation is on the order of 10–4 kg/m2 · s. The apparent activation energy of oxidation, depending on the amount of modifiers in the alloys, is: for AL2 alloy – 56.52–43.75, for AL4 alloy 59.74–37.09, for AL9 alloy 61.40–39.90 kJ/mol. The mechanism of influence of strontium on the kinetics of oxidation of melts AL-2, AL4 and AL9 has been established. Aluminum oxide Al2O3 plays a dominant role in the formation of a protective oxide film.