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In this study, WC10Co4Cr (particle size $45\pm 15$$\mu$m) and WC10Co4Cr+Graphen nano-platelets (GNPs) of particle size $15\pm 10$$\mu$m cermet coatings were deposited on an ASTM A479 steel substrate utilising the High-Velocity Oxygen Fuel (HVOF) technique. The wear and corrosion of coated and uncoated surfaces were studied using the pin-on-disc and salt spray testing methods, respectively, and the micro-hardness of the cross-sections was tested using a Vickers micro-hardness testing machine at an applied force of 10N. Further, surface morphology of coated and uncoated substrate was investigated using scanning electron microscopy (SEM) and microscopic images. The analysis revealed that WC-10Co-$4\mathrm{\text{Cr}}+\mathrm{\text{GNPs}}$-coated (C2) surfaces outperformed WC10Co4Cr coated (C1) surfaces in terms of wear resistance.

An atmospheric plasma spray deposition process was adopted for coating regular-shaped, Stellite 6 powder directly on a rolled 3mm size AISI 304 austenitic grade stainless steel substrate without any intermediate bond layers. Coating thickness as measured in a scanning electron microscope was obtained as 74 $\mu$m, 128 $\mu$m, and 215 $\mu$m. An experimental investigation of the functional behavior such as corrosion, microhardness, and erosion of the coated steel at different operating temperatures was undertaken to determine the suitability of its application in the industry. Erosion tests were conducted in an air jet tribo-tester utilizing alumina as an erodent with normal impingement angle at room temperature, 300^∘C, and 600^∘C. It was difficult to identify a single coating thickness that can be satisfactorily used for superior erosive wear properties with corrosion resistance. So modern management tools such as tri-vector and technology sieve analysis procedures as identification techniques were adopted for the selection of the best coating thickness by complying with the mechanical, erosion, and corrosion resistance properties. Steel coated with 128-$\mu$m coating thickness provides the best result for a combination of functional characteristics.

Automobile structural components are subject to high stress, friction and corrosive environmental conditions. Though aluminum alloys exhibit lightweight and high corrosion resistance, there is a need to improve the high strength-to-weight ratio and resistance to friction. This paper presents microstructural analysis, hardness, dry sliding wear behavior, and corrosion behavior of AA7075 reinforced with silicon carbide (SiC) particles. The composite specimens were prepared at the concentration of 2.5 and 5wt.% SiC. The microstructure of AA7075 showed dendritic morphology while composite specimens showed nondendritic morphology grains. Reinforcement of SiC resulted in increased nucleation site and refinement of grain during solidification. XRD analysis of base alloy showed $\alpha$ matrix with $\eta$ (MgZn₂), T(Al–Zn–Mg–Cu) and Al₇Cu₂Fe phases, while the composite sample showed the presence of additional S(Al₂CuMg) and $\theta$ (Al₂Cu) phases. Composite samples showed higher hardness values than base alloy due to grain boundary strengthening and Orowan strengthening. The enhancement of hardness of AA7075 by 20% and 37.5% were obtained with the addition of 2.5 and 5wt.% SiC particles respectively and also predicted with less coefficient of friction and less wear rate at all the tested load conditions. At the same time, the respective reduction in wear rates of AA7075 was found to be 50 and 65%. The worn-out surface of the base alloy was found to have undergone extensive plastic deformation and resulted in delamination with extensive patches and no clear groove marks. The composite sample of 2.5wt.% SiC showed mild patches with clear groove marks, while the Composite of 5wt.% SiC showed groove marks with fine width parallel to sliding directions. The wear mechanism was found to be transferred from adhesive mode to abrasive mode through a mixed mechanical layer with an added concentration of SiC particles from 0wt.% to 5wt.%. Weight loss during immersion corrosion increases with an increase in the amount of SiC due to an increased amount of metallic phase which increases microgalvanic corrosion and pitting. Hence, composite samples showed decreased corrosion resistance than base alloy.

Cold spraying is a promising technique for depositing wear-resistant coatings on components like hydroturbine steels. This paper highlights the feasibility of hard WC-17Co coating on 13Cr4Ni hydroturbine steel. The coating was deposited at 25, 30, and 40 bar at 800^∘C and 50 bar at 900^∘C. Further, different characterization techniques (SEM, XRD) were used to analyze the developed coatings. The Vicker hardness testing was employed to determine the hardness of the coated sample. It was observed that WC-17Co coatings deposited at 40 bar and 800^∘C offered a maximum hardness of up to 275 Hv, which is an excellent quality for anti-wear applications in hydro turbine blades.

Two chemical solutions NH₄F:H₂O:C₃H₈O₃(sol${}_1)$ and NH₄F:H₂O:C₂H₆O₂(sol${}_2)$ with different fluoride ratios were used separately in an anodic process to study the morphological characteristics of the produced copper oxides. Glycerol and ethylene glycol were utilized as inhibitions to slow down the activity of fluoride ions. The rest of the anodization process parameters were constant. Scanning electron microscope (SEM) images showed the formation of Cu₂O microcubes when sol₁ was used. The utilization of sol₂ produced octahedral Cu₂O as well as cubes and spherical structures. The increase of NH₄F in sol₁ led to a reduction in the volumes of Cu₂O microcubes, and in sol₂, it produced incomplete octahedral Cu₂O. Since ethylene glycol has a lower viscosity than glycerol, copper corrodes more quickly in the presence of the former than in the latter. The findings indicate that sol₁ is experiencing a higher current flow than sol₂. The relationship between current and time is semi-constant at low applied voltage, but the two curves behave differently when applying high voltage in the early stages.

In this work, laser cladding on H13 tool steel substrate with two different powder compositions CrNiW and CrNiFeAlZr has been carried out. The optimal deposition conditions were acquired for corrosion, wear, and residual stress study. The untreated surfaces showed deeper grooves in the wear analysis. This demonstrated that the untreated substrate surface had a high degree of plastic deformation, confirming lower wear resistance to abrasion. In contrast to the untreated substrate specimen, the CrNiW and CrNiFeAlZr laser-clad samples displayed increased wear resistance. Compared to the H13 steel substrate, the coated samples exhibited significantly lower coefficient of friction and superior wear resistance. Furthermore, increased corrosion resistance was demonstrated by both coatings in a 3.5% NaCl solution. The coated specimens had a higher $E_{\mathrm{\text{corr}}}$ value than the substrate. In contrast, the $i_{\mathrm{\text{corr}}}$ value of the coating was lower than base metal. It is proposed that the compressive residual stress that was produced on the surface of CrNiW clad specimen was caused by the disparity in the substrate and surface rates of cooling during the cladding process.

Aluminum alloy was subjected to anodization and then treated with a mixture of dodecanoic acid and aluminum sulfate, which produced an aluminum alloy that was extremely hydrophobic. Using energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM), the surface structure and composition of the aluminum alloy samples were examined. The results showed that the dodecanoic acid and aluminum sulfate mixture-treated aluminum alloy surface underwent etching while also absorbing aluminum dodecanoate, resulting in a micro–nano conical nonuniform structure. With a static contact angle (CA) of 156${}^{\circ }$, the superhydrophobic aluminum alloy has exceptional anti-icing and self-cleaning qualities. When compared to anodized aluminum alloys, the superhydrophobic aluminum alloy exhibits improved corrosion resistance in a 3.5wt.% NaCl solution.

A thin passive titanium dioxide, in its stoichiometric form, has a very high corrosion resistance, but the same conclusion can not be made on corrosion resistance of a surface which is not stoichiometrically titanium dioxide, or even a surface which is a composition of various elements and oxides. In practice, the implants available on the market have an oxide surface contaminated with other elements. The aim of this paper is to correlate clinical observations that show the deterioration of Ti made implants after certain period of insertion in the patients, and in vitro corrosion resistance of Ti implants with surface passive oxide layer. For this purpose, surface analysis of the retrieved failed implants were performed and in vivo animal experiments with relation to ion release from implants were done. Finally, on the basis of the clinical observation, in vivo animal test, and in vitro electrochemical corrosion test, a model is proposed to explain the corrosion and ion release from the Ti implant.

We made a comparative study of the elements in the periosteum on titanium plates and screws for internal bone fixation, normal periosteum, and oral mucosa by the PIXE method. We studied 11 patients, 4 men and 7 women, with mandibular fracture or facial deformity. The implanted time length of the materials in the body was 5 to 16 months. The analyzed samples were 11 periostea on the materials, 11 normal periostea and 4 oral mucosae. The results were as follows. Twenty-four essential and 11 contaminated elements were detected in the periostea on the materials as well as in the normal periostea and the oral mucosae. In the mean values of titanium and aluminum, there were significantly higher values in the periostea on the materials than in the normal periostea. The mean concentration values of the other elements did not differ significantly between that in the periostea on the materials and that in the normal periostea. The concentration of titanium in the periostea on the materials was not correlated with sex, age of the patients, or the implanted time length. However, there was a significantly higher titanium concentration value in the periostea on the plates than on the screws. Our results could indicate that the existence of a titanium element in the periostea on the materials was caused by its dissolution from the materials.

The influence of anodized film on corrosion and electrochemical behavior of extruded magnesium alloy AZ63, cast and die-cast magnesium alloys AZ91D were investigated by using immersion technique, electrochemical methods, SEM, EDAX, IR and XRD. The results showed anodized film could improve remarkably corrosion resistance. Protection effect was different with the same anodizing process because formation status of anodized film of different materials was different. The formation status of anodized film was related to alloy microstructure as revealed by optical and scanning electron microscopy. The formatting process and casting method strongly influences the corrosion performance by affecting on the alloy microstructure. A tentative corrosion mechanism is presented explaining the corrosion behavior of anodized magnesium alloy.

A soft approach has been described for the formation of α–Fe₂O₃ nanorods by simple reaction of iron with water at a very low temperature range of 100–300°C. It is shown that the nanorods have diameters ranging from 50–80 nm, and their typical lengths are in the range of 5–10 μm. The chemical composition and crystalline structure of nanorods were investigated by various characterization techniques. The initial formation and subsequent growth of α–Fe₂O₃ nanostructures may be explained by the iron metal corrosion mechanism.

High current pulsed electron beam (HCPEB) has been developing as a useful tool for surface modification of materials. This paper presents our research work on surface modification of metallic materials, such as mold steel, stainless steel and magnesium alloy, with a HCPEB equipment of working parameters as electron energy 27keV, pulse duration ~1µs and energy density ~5J/cm². Investigations performed have shown that the most pronounced changes of phase-structure state and properties occurring in the near-surface layer. The formation mechanism of surface craters and their evolution regularity are discussed based on the elucidation of non-equilibrium temperature filed and different kinds of stress formed during pulsed electron beam treatment. After the HCPEB treatments, samples show significant improvements in measurements of wear and corrosion resistance.

Magnesium is light, biocompatible and has similar mechanical properties to natural bone, so it has the potential to be used as a biodegradable material for orthopedic applications. However, pure magnesium severely corrodes in a physiological environment, which may hinder its use for in vivo applications. Protective coatings are effective method to delay the corrosion of Mg. In this study, sol-gel and hydroxyapatite (HA) coatings were applied onto the surface of pure magnesium substrates using a biomimetic technique. The corrosion rate of surface-treated substrates was tested. It was found that both types of coatings substantially slowed down the corrosion of the substrate, the 60Ca so-gel and HA coating was more effectively than the 100Si so-gel and HA coating in hindering the degradation of the substrate. Thus, the corrosion rate of magnesium implants can be closely tailored by coating sol-gel then coating apatite thereby monitoring the release of magnesium ions into the body.

Electrochemical measurement and surface analysis methods were employed to investigate the Microbiologically Influenced Corrosion (MIC) influenced by Thiobacillus ferrooxidans biofilm. Electrochemical impedance spectroscopy (EIS) results indicated that the impedance value of steel A3 after 21 days of immersion in sterile solution was much higher than that of T.f solution. Atomic Force Microscopy (AFM) results showed the adsorption state of the microorganism on the metal surface for 7 days of exposure in T.f solution. The morphologies of the surface film were analyzed with the Scanning Electron Microscope (SEM), which showed the changes with exposure time of the film on the metal surface. The special morphology and the heterogeneity of Thiobacillus ferrooxidans biofilm induced the localized corrosion of steel A3. After 21 days of exposure, general corrosion occurred in the sterile solution, while localized corrosion was detected under the effect of Thiobacillus ferrooxidans.

Through investigating the corrosion fatigue crack initiation behavior of A7N01P-T4 aluminum alloy welded joints in 3.5 wt.% NaCl solution, corrosion fatigue crack initiation life is formulated as $N_i=6.97\times 10^{12}{[\mathrm{\Delta }{\sigma }_{\mathrm{\text{eqv}}}^{1.739}-{49}^{1.739}]}^{-2}$ and the mechanism of corrosion fatigue crack initiation is proposed. SEM and TEM tests revealed that several corrosion fatigue cracks formed asynchronously and the first crack does not necessarily develop into the leading crack. The uneven reticular dislocations produced by fatigue loading are prone to piling up and tangling near the grain boundaries or the second phases and form the “high dislocation-density region” (HDDR), which acts as an anode in microbatteries and dissolved to form small crack. Thus the etching pits, HDDR near the grain boundaries and second phases are confirmed as the main causes inducing the initiation of fatigue crack.

The effect of compressive deformation on thermal stability and corrosive property of Zr${}_{61.7}$Al₈Ni${}_{13}$Cu${}_{17}$Sn${}_{0.3}$ bulk metallic glass with a strain of 80% was investigated in this work. The corresponding thermal stability is found to decrease after deformation and this can probably be attributed to the reduction of the viscosity and the increase of the Gibbs free energy after compressive deformation. In addition, the corrosion current density increases and this suggests that the corrosion resistance decreases for the deformed sample in comparison with the as-cast sample.

Equiatomic and near equiatomic NiTi alloys, showing good mechanical and thermal shape memory properties, are widely exploited in different industrial applications. In addition, NiTi alloys have promising anti-cavitation and corrosion-resistance properties. These advantages have provided opportunities to exploit NiTi alloys as the coatings for protecting materials used in the industrial applications. This study is a preliminary investigation aiming to evaluate the feasibility to form NiTi alloy coatings on SS304 steel by tungsten inert argon arc welding (TIG) technology. The microstructure analysis shows that the crystalline phases in NiTi coatings on SS 304 steel are TiNi-B2, TiNi-B19’ and Ni₃Ti. The potential of the NiTi coatings to enhance the corrosion resistance and cavitation resistance behaviors of steel exposed to seawater is studied. NiTi coatings, with two different thicknesses of about 1.2 and 2 mm, having homogenous microstructures were successfully deposited on SS304 steel using TIG technology. Results of tests, done in aqueous solutions simulating seawater, showed that the formation of the oxide films on the surface of NiTi coatings increased the corrosion resistance and wear resistance and decreased the damage caused by the cavitation. Moreover, it was understood that the NiTi coatings with 2 mm in thickness show the superior performances than those with 1.2 mm in thickness. The tribological mechanisms responsible for the unique properties of NiTi alloy coatings were investigated. The wear-resistance behaviors of NiTi alloy coatings are greatly influenced by the friction conditions. Increasing load decreased CoF and the wear rate of the coatings were almost constant, which was attributed to the pseudoelasticity of NiTi alloy. The attractive properties of NiTi alloys that makes it most influential materials for industrial applications have also been discussed.

Supersonic atmospheric plasma spraying (SAPS) is a newly developed technique in preparing high-performance Cr₃C₂–NiCr coatings with a high deposition efficiency. In this work, the effect of post-heat treatment on carbide precipitation and corrosion property of the SAPS Cr₃C₂–NiCr coatings was investigated. The results suggested that heat treatment induced the precipitation of secondary carbide grains, and the size of these carbides increased with the increasing heat treatment temperature. In addition, the self-corrosion current density of the coatings thermally treated at 500^∘C was seven times smaller than that of the coating without heat treatment. The corrosion morphology showed that significant corrosion cracks were present on the as-sprayed coating. In contrast, the heat-treated coatings demonstrated small corrosion holes due to the formation of small corrosion galvanic cells between the precipitation of carbides and the substrate.

The dissolution of xCaO · (90-x)P₂O₅ · 10K₂O glasses (x≤35 mol%) in simulated biological media (decationized water, physiological serum and chlorine acid, pH=1.5), at room temperature, in static regime during 24 h was investigated. The data indicates that the corrosion behavior of the samples depends on the pH of the solutions, glass composition and local structure. In the investigated time range, one observes two leaching stages relative to the incipient dissolution. In the first stage, the lowest release rate is obtained from the potassium-phosphate matrix in decationized water, while for the whole time the lowest leaching rate is recorded again in decationized water but from the sample containing small amount of lime, with CaO/P₂O₅ ratio of 0.06. When the substitution of P₂O₅ by CaO exceeds 50%, the release behavior changes in the investigated media.

This experiment has examined the corrosion and tribological properties of basalt fiber reinforced composite materials. There were slight changes of weight after the occurring of corrosion based on time and H₂SO₄ concentration, but in general, the weight increased. It is assumed that this happens due to the basalt fiber precipitate. Prior to the corrosion, friction-wear behavior showed irregular patterns compared to metallic materials, and when it was compared with the behavior after the corrosion, the coefficient of friction was 2 to 3 times greater. The coefficient of friction of all test specimen ranged from 0.1 to 0.2. Such a result has proven that the basalt fiber, similar to the resin rubber, shows regular patterns regardless of time and H₂SO₄ concentration because of the space made between resins and reinforced materials.