Annealed Coatings Research Articles

Mechanical properties dependence on the modulation period in multilayered TiN/ZrN coatings

This article presents results from a study on the properties of nanostructured multilayered TiN/ZrN coatings with different modulation periods deposited by cathodic-arc evaporation from Ti and Zr targets in nitrogen atmosphere on high-speed steel substrates. The thickness of the TiN-ZrN bilayers varied from 12 nm to 52 nm depending on the rotation speed of the holder. In order to investigate the effect of heat treatment on the mechanical and structural properties, the multilayer ZrN/TiN coatings were annealed in Ar atmosphere at different temperatures for two hours. The surface morphology, elemental composition, nano-hardness and adhesion strength of the as-deposited and annealed coatings were analyzed by scanning electron microscopy complemented with energy dispersive X-ray spectroscopy analysis, and nanoindentation and micro-scratch tests. The results obtained show that the mechanical properties of multilayer TiN/ZrN coatings are considerably improved in comparison to those of the monolayer ZrN and TiN coatings.

Investigation of Single-Particle Erosion Behavior of Electroless Ni-P-Ti Composite Coatings

Electroless Ni-P-Ti composite coatings were deposited on AISI 1018 steel substrates by incorporating Ti nanoparticles into a Ni-P matrix. It was then followed by annealing to form the NiTi intermetallic precipitates within the coatings. In this study, single-particle erosion behavior of both as-deposited and annealed coatings was investigated. It was found that the erosion behavior of the coatings changes from a brittle (as-deposited) to a ductile erosion behavior (annealed) due to the formation of superelastic NiTi phase. Stress distribution during the single-particle impact process was calculated to facilitate the understanding of toughening and erosion mechanisms. Crack shielding and crack closing induced by transformation toughening were observed in the vicinity of the impact crater on the annealed 11.8 wt.% coating. This study discusses the erosion and toughening mechanisms of Ni-P-Ti composite coatings.

Effect of heat treatments on the mechanical and tribological properties of electrodeposited Fe–W/Al2O3 composites

In this study, the influence of heat treatment on the mechanical and tribological properties of electrodeposited Fe–W/Al2O3 composite coatings is studied. The properties of the as-deposited and annealed composites are compared with those of electrodeposited hard chromium coatings. The amorphous structure of the Fe–W matrix transforms into a mixed amorphous-crystalline structure upon annealing at 600 °C for 1 h. The observed microstructural transformations result in a substantial increase of both the hardness and the reduced Young's modulus of the Fe–W/Al2O3 composite coatings, reaching values of 16.3 GPa and 191.7 GPa, respectively. The results on the wear resistance studied under dry friction using ball-on-disc sliding tests show that a low wear rate is obtained for both as-deposited and annealed composite coatings, i.e. ~1.5 × 10−6 mm3/Nm. In contrast, the heat treatments are detrimental for both the hardness and wear resistance of hard chromium coatings. As a consequence, the mechanical and wear properties of the electrodeposited Fe–W/Al2O3 composite coatings, especially after annealing, are superior to the properties of hard chromium coatings. Hence, Fe–W/Al2O3 composite coatings can be considered as a valid and sustainable alternative to hard chromium coatings, particularly in applications where these materials may be exposed to high temperatures.

Microstructure and wear behavior of FeCoNiCrMn high entropy alloy coating deposited by plasma spraying

FeCoNiCrMn high entropy alloy coatings were deposited on steel substrate by atmospheric plasma spraying at different H2 flow rates and subsequently annealed. The microstructure and the phase composition of the prepared coatings were investigated, and the hardness of the coating was determined. The wear behavior of the as-sprayed and annealed FeCoNiCrMn coatings against WC-Co ball was evaluated under dry sliding condition. The results show that the fluffy structures characterized on the surfaces of as-sprayed coatings were formed due to the volatilization and oxidation of Mn element. The coatings were single FCC phase along with some oxides. The wear rate of the as-sprayed coatings was reduced by half as the H2 flow rate increasing from 3 to 6 L/min. Annealing can greatly improve the wear resistance and scratch resistance of the as-sprayed coatings. The characterization of wear tracks demonstrates that splat spalling was the dominating wear mechanism for the as-sprayed coatings. The improvement of wear resistance by increasing H2 flow rate and annealing was attributed to the enhancement of cohesive strength among splats.

Homogeneous annealing of TiO2, ZrO2 and ITO sol-gel layers with CO2 laser

Laser annealed sol-gel layers have the potential to replace the furnace process and expand the field of applications for selective annealed sol-gel coatings. In this study laser annealed TiO2, ZrO2 and ITO layers on glasses are investigated. Processing parameters of the CO2-laser system such as scanning speed, line overlap, laser power and focal spot are evaluated to generate sufficient thermal energy for densification. The ITO annealing process results in a sheet resistance comparable with the furnace annealed samples. Microscope images of the TiO2 and ZrO2 samples show a homogeneous layer morphology. XRD images exhibit crystalline tetragonal ZrO2 as seen in thermally annealed layers.

Correlation between Defect Density and Corrosion Parameter of Electrochemically Oxidized Aluminum

It has been recognized that a connection may exist between defects of oxide coating and its corrosion protection. Such a link has not been substantiated. We prepare two coatings of anodized aluminum oxide (AAO) and plasma electrolytic oxidation (PEO), and analyze them with Mott-Schottky plots and potentiodynamic polarization scans. The as-grown and annealed AAO coatings exhibit both p-type and n-type semiconductor behaviors. Polarization resistance of the AAO coating increases from (1.8 ± 1.7) × 108 to (4.3 ± 0.5) × 108 Ω·cm2, while corrosion current decreases from (6.1 ± 3.6) × 10−7 to (2.3 ± 0.9) × 10−7 A·cm−2, as annealing temperature increases from room temperature to 400 °C. The parameter analysis on AAO indicates a positive correlation between corrosion current and donor density, a negative correlation between polarization resistance and donor density. The attempt on correlating corrosion potential gives rise to considerable deviation from a linear fit. The results suggest protection of AAO hinges on its donor density, not acceptor. On the PEO coatings, only the n-type behavior is observed. Intriguingly, the donor density of PEO coating is influenced by the annealing temperature of its pre-anodized layer. The most resistant PEO coating, with pre-anodized and 400 °C annealed AAO, exhibits polarization resistance (2.1 ± 0.4) × 109 Ω·cm2 and corrosion current (1.7 ± 0.4) × 10−8 A·cm−2.

Effect of heat treatment on friction and wear behavior of Ni-based thermal spray coating deposited on Z200C12 steel

The present work investigates Ni-based alloy coating deposited on Z200C12 steel using thermal spray technique. It focuses on the effect of annealing treatment at 500 °C for different durations of 2 h, 4 h and 8 h on friction and wear behavior of the coatings. Phase composition, substrate/coating interface, elemental distribution and coating wear tracks morphologies were characterized using x-ray diffraction, scanning electron microscope, energy dispersive spectrometer and x-ray mapping techniques. Friction and wear resistance of the as-sprayed and annealed coatings were studied by determining the coefficients of friction and wear rates using an Al2O3 ball under a load of 6 N. The results showed that the heat-treated coating at 500 °C for 2 h exhibited the highest wear resistance and a substantially lower friction coefficient as compared to all other coatings. The observed wear mechanisms mainly involved fragmentation of splats, brittle fracture, and abrasive wear.

Electrophoretic deposited graphene based functional coatings for biocompatibility improvement of Nitinol

Shape memory effects and superelastic nature of Nitinol alloy has been exploited in various biomedical applications. However, prolonged usage of this implant material is restricted due to the toxic effect of released Ni-ions (Ni2+) into tissue environment. This reduces the biocompatibility of the material. The purpose of this study was therefore to assess the effect of graphene coatings on the biocompatibility of Nitinol wires used as dental braces. The graphene coating was prepared on Nitinol substrate through cathodic electrophoretic deposition (EPD). Isopropyl alcohol and magnesium nitrate hexahydrate (Mg(NO3)2•6H2O) were used as a dispersion medium and charging agent for the EPD process respectively. The surface morphology, structure, surface roughness and corrosion resistance behavior of as-deposited and annealed graphene coatings were investigated. As-deposited sample presents a rough surface with visible microcracks and fine pores, while annealed sample possesses a smooth surface with no visible microcracks and pores. The annealed sample showed better results than the as-deposited sample in terms of mechanical strength as observed from Nanoindentation test. Furthermore, Potentiodynamic polarization test was conducted in a simulated body fluid environment to evaluate the corrosion resistance behavior of bare Nitinol substrate and graphene coatings. From the test results, we have found that corrosion potential of a bare Nitinol substrate, as-deposited and annealed sample is around -510 mV, -375 mV and -261 mV respectively. This positive shift in corrosion potential highlighted the improvement in corrosion resistance property of Nitinol substrate by graphene coatings. This indicates the suitability of EPD coated graphene as an effective coating material for biomedical applications.

Resonant Raman scattering characterization of thermally annealed HiPIMS deposited MoSx coatings

Raman spectroscopy is used to investigate the structural and tribological properties of HiPIMS sputtered MoSx thin films which were post-growth-annealed at different temperatures. The Raman scattering combined with X-ray diffraction determines a reduction in the residual strain within the MoSx layers with increasing annealing temperature. In the high-temperature annealed coatings a Raman signature at 40 cm−1 emerges, which results from a strengthening of the inter-layer van-der-Waals interaction. This observation indicates that the thermally annealed MoSx thin films become more resistant against shear forces, which is manifested in an increase of the coefficient of friction measured with a ball-on-disc tribometer. The coefficient of friction moreover decreases with lowering the sulfur/molybdenum ratio which, in turn, depends on the substrate and annealing temperatures. Furthermore, a Raman forbidden mode may be exploited to detect stacking faults within the sputtered coatings. Its observation is realized through resonant excitation of an MoS2 exciton at about 633 nm.

Mechanical properties and microstructural stability of CuTa/Cu composite coatings

In this study, the structure and mechanical properties of as-deposited and 823.15 K annealed CuTa coatings were studied with the purpose to evaluate the microstructural and mechanical thermal stability as a function of the Ta content. CuTa coatings with a Ta content from 0 to 100% were prepared by magnetron co-sputtering. Their structure and mechanical properties were characterized by grazing angle X-ray diffraction (XRD), scanning and transmission electron microscopy (TEM), and nanoindentation. The XRD results show that a Ta-rich CuTa glass metal is formed in the coatings with 15–67 at.% Ta along with nanocrystalline Cu and such microstructure was retained after vacuum annealing at 823.15 K. TEM analyses of selected samples showed the formation of crystalline Cu islands in an amorphous CuTa matrix in both as-deposited and annealed coatings. The coatings presented a 3D distribution of Cu nanocrystals within an amorphous CuTa matrix which might reduce the brittleness of the glassy CuTa matrix. A significant increase in hardness values from 0.9 GPa for pure Cu to 11.9 GPa for the sample with 98 at.% Ta is observed. It has been shown that the composite coatings preserved the microstructure and were mechanically stable after vacuum annealing.

Corrosion and Algal Adhesion Behaviors of HVOF-Sprayed Fe-Based Amorphous Coatings for Marine Applications

In this study, Fe-based amorphous/nanocrystalline coatings consisting of Fe53Cr19Zr7Mo2C18Si were fabricated by high-velocity oxy-fuel spray. For comparative study, further crystallization annealing treatment at 750 °C was carried out for the coatings. The microstructure, corrosion resistance and algal adhesion behaviors of the as-sprayed and annealed coatings were systematically investigated by scanning electron microscopy, x-ray diffraction, transmission electron microscopy, electrochemical testing and laser confocal scanning microscopy, respectively. Results show that the as-sprayed coatings exhibited excellent corrosion resistance and decreased algal adhesion, while the annealed coatings displayed compromised anti-corrosion performances, but significantly inhibited the adhesion of typical algae Phaeodactylum tricornutum.

Trivalent chromium electrodeposition using a deep eutectic solvent

PurposeThis paper aims to investigate the electrolytic deposition of corrosion-resistant chromium coatings from a trivalent chromium plating bath based on deep eutectic solvent, a new generation of room temperature ionic liquids.Design/methodology/approachThe electrolyte contained chromium (III) chloride, choline chloride and the additive of extra water. The surface morphology was estimated by means of SEM technique. The microstructure of as-deposited and annealed coatings was studied using X-ray diffraction method. The kinetics of the chromium electrodeposition and the corrosion electrochemical behavior of the coatings were investigated by cyclic voltammetry technique.FindingsChromium coatings with an amorphous type of microstructure are electroplated from this bath. Some carbon and oxygen are included in deposits obtained. The step-wise mechanism of the electrochemical reduction of Cr(III) ions to Cr(0) is detected. The current efficiency in this system sufficiently exceeds that typical of usual aqueous electrolytes. The coatings fabricated using plating bath based on deep eutectic solvent showed enhanced corrosion resistance in an acidic medium: there is no current peak of active dissolution in polarization curve and the corrosion potential shifts to more positive values as compared with “usual” chromium.Originality/valueThe electrodeposition of chromium coatings from an environmentally acceptable trivalent chromium electrolyte, a deep eutectic solvent containing chloride choline and extra water additive has been investigated for the first time.

Tuning Interface to Improve Corrosion Resistance of Electroless Ni-P Coating on AZ31B Alloy

Interface is crucial to enable desirable service performances of coatings on substrates. In this paper, Ni-P coatings were prepared on AZ31B alloy by using electroless plating, with the coating/substrate interface being tuned to improve the corrosion resistance. The interface tuning involved a phosphate treatment prior to the electroless plating, which created a uniform surface of the Mg substrate and finally led to Ni-P plating coatings with enhanced density during the electroless plating. Electrochemical testing was performed to compare the corrosion properties between the Ni-P coatings with and without phosphate treatment. The experimental results evidently showed that the introduction of phosphate treatment, especially after an annealing treatment, greatly improved the corrosion resistance. The underlying mechanisms, revealed by microstructural examinations, were that the phosphate treatment reduced the substrate surface roughness and likely promoted a high and uniform nucleation intensity of the Ni-P coating. Corrosion processes of the unannealed and annealed Ni-P coatings with an interfacial phosphate layer were further clarified for comparison.

Deposition and characterization of phase-pure Ti2AlC and Ti3AlC2 coatings by DC magnetron sputtering with cost-effective targets

Ti2AlC and Ti3AlC2 coatings were successfully prepared via a two-step method with initial DC magnetron sputtering at ambient temperature and post annealing at 800 °C for 1 h. Particularly, cost-effective targets synthesized by hot-pressing Ti/Al/C powders at low temperature (800 °C) were used. The phase components and microstructure of the coatings were characterized by XRD, laser Raman spectroscopy, SEM and TEM. It was found that the phase components of the as-deposited and annealed coatings varied with the molar ratio of Ti, Al and C powders in the cost-effective targets. Phase-pure Ti2AlC and Ti3AlC2 could be obtained from the target with the Ti:Al:C molar ratios of 2:1.5:1 and 3:2:2, respectively. These two coatings were consisted of plate-like grains. Due to the high internal stress resulting from crystallization- or phase transformation-induced volume change, both of the Ti2AlC and Ti3AlC2 coatings cracked during the annealing process.

热处理对火焰喷涂Fe-Ni-Al 合金涂层组织和摩擦性能的影响

The Fe-based coatings in powder form were deposited on a steel type E335 by flame spraying technique. The effects of the post heat treatment on the microstructure and the mechanical properties of sprayed coatings were studied. Post heat treatment was conducted in a furnace in air at 623 K, 823 K and 1023 K for 1 h and then cooled in air. The results showed that with the increase of annealing temperature, the microstructure of coating treated at 823 K and 1023 K had several changes as follows: the reduction of porosity, formation of carbides and oxides. It was found that the solid solution FCC (Fe, Ni), intermetallic compound AlFe3 and carbides [Fe, C] were the main phases for coatings as-sprayed and treated at 623 K and while iron carbide, molybdenum carbide and oxide as Fe3O4 became the main phases and reinforced the solid solution FCC (Fe, Ni) phase for annealed coatings at 823 K. However, it was observed the disappearance of molybdenum carbide and oxide Fe3O4 at 1023 K. The coating annealed at 823 K exhibited an excellent wear resistance than the as-sprayed and annealed coatings at 623 K and 1023 K and shows the lower wear rate than another coating treated or as sprayed.

Pulsed Electron Deposition of nanostructured bioactive glass coatings for biomedical applications

Abstract Due to poor mechanical properties and brittleness of bioactive glasses, the deposition of bioactive glass coatings on bioinert metallic implants for bone regeneration is a promising route to combine the high bioactivity of the glassy phase with the mechanical strength of metallic substrate. The Pulsed Electron Deposition (PED) technique has been recently demonstrated to be an effective method to fabricate highly-adherent and nanostructured bioactive thin films and coatings, with fine control over film composition. In this paper, we investigated the deposition by PED of 45S5 Bioglass ® and of a novel CaO-rich bioactive glass, also containing potassium oxide. Composition, microstructure, surface morphology, wettability and adhesion to the titanium substrate were assessed for both as-deposited and annealed coatings. All samples exhibited a nanostructured surface morphology and high hydrophilicity, both positive features for biological applications. In particular, annealed samples exhibited increased roughness and adhesion degree to the titanium substrate compared to the as-deposited ones. The results showed in this paper suggest that bioactive glass coatings deposited by PED are promising for being further investigated as bioactive coatings for bone implants.

Multilayer structures based on annealed electrospun biopolymer coatings of interest in water and aroma barrier fiber‐based food packaging applications

ABSTRACTIn this research work, for the first time, a fiber‐based packaging material was coated by annealed electrospun ultrathin fibers of poly(3‐hydroxybutyrate), poly(vinyl alcohol), and polylactide. The resultant mono‐ and multilayer structures self‐adhered to the paper substrate and were characterized in terms of morphology, optical, and barrier properties. Additionally, the use of a static flat plate and rotating mandrel collector as well as the application of different electrospinning deposition times were analyzed. The thermally treated electrospun biopolymers yielded totally transparent films while, due to the opaque nature of the uncoated paper substrate, the developed packaging materials were also opaque but with a glossier surface finish provided by the bioplastic coating. The annealed films obtained from random electrospun fibers, that is, the mats of ultrathin fibers collected on the static plate, presented higher transparency and thickness and also enhanced barrier performance. On the overall, the developed annealed electrospun biopolymer coatings resulted in a significant improvement of the paper barrier properties to water and limonene vapors, being the paper/poly(vinyl alcohol)/poly(3‐hydroxybutyrate) film the best performing multilayer packaging structure. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45501.

Microstructure and electric properties of low-pressure plasma sprayed β-FeSi2 based coatings

Thermoelectric material β-FeSi2 based coating was fabricated by the technique low-pressure plasma spray (LPPS) on the Al2O3 substrate from different alloy powders. During the process LPPS, the phase transformation had occurred through the peritectoid, eutectoid reaction and their inverse reaction. The grain size of the as-sprayed β-FeSi2 doped Co coatings was reduced comparing with the original feedstock powders, which implied the thermal conductivity could effectively decreased by the LPPS process. The room temperature electrical conductivity showed metal and semiconductor properties on the as-sprayed and annealed coatings. This method and the results could solve the problems of practical application especially on special-shaped surfaces such as the automobile exhaust pipe or other complex surface shape of the device.

The effect of electron irradiation and post-irradiation annealing on α-Al2O3 coating prepared by MOD method

α-Al2O3 ceramic coatings were prepared by a novel metal organic decomposition (MOD) method on 316L stainless steel. Effects of electron irradiation and post-irradiation annealing process on the surface morphology, composition, phases and corrosion resistance of the coating were studied by using AFM, FESEM, EDS, XRD and electrochemical workstation. The results show that the surface of α-Al2O3 ceramic coating was roughened after irradiation and then smoothed after subsequent annealing. The oxygen content of the coating was highly decreased after electron irradiation and then increased after subsequent annealing. The FeO phase of the coating was disappeared after irradiation and re-formed with the disappearance of AlFeCr phase after subsequent annealing. Both the irradiated and post-irradiated annealed coatings behaved superior corrosion resistance and protective ability compared to the original counterpart due to microstructure modification induced by irradiation. Meanwhile, two electrical circuit models were proposed to simulate the EIS results to explain the corrosion mechanism of the coatings.

Structure and thermal stability of spectrally selective absorber based on AlCrON coating for solar-thermal conversion applications

A novel four-layered Mo/AlCrON(HMVF)/AlCrNO(LMVF)/AlCrOx tandem coating was designed and fabricated by cathodic arc ion plating for solar-thermal conversion applications. The chemical composition, structures and thermal stability of the coating were systematically investigated by SEM, EPMA, XRD, TEM, XPS and Raman. The optical properties of the as-deposited and annealed coatings were measured by spectrophotometers. The high-temperature emittance of the coating was measured by a steady-state measurement system. Results showed that tandem coating exhibited a high solar absorptance of 0.921, and a low emittance of 0.12 at 25°C, as well as emittance of 0.26–0.35 at temperatures range of 300−519°C. The structure analysis showed that the nano-multilayered structured HMVF and LMVF layers, acting as the main absorber, were consisted of the Cr2Al nanograins embedding in the amorphous AlCrON phases. While the top AlCrOx layer was amorphous in nature, and could act as an antireflection layer. After heat-treatment at 600°C in air for 7 days, only slight microstructure changes were observed from the tandem coating, and very similar solar selectivity of 0.922/0.14 to the as-deposited one was obtained, which indicated the relatively good thermal stability of the coating. These results indicated that the coating could be possibly applied to the high temperature solar-thermal conversion system.