Microstructure Of Coatings Research Articles

Effect of Laser Parameters on the Microstructure and Properties of CoCrFeNiMn High Entropy Alloy Coatings

Effect of Laser Parameters on the Microstructure and Properties of CoCrFeNiMn High Entropy Alloy Coatings

Effect of Ti addition on the microstructure and corrosion behavior of laser cladding AlCoCrFeNi high-entropy alloy coatings

AlCoCrFeNi high-entropy alloys (HEAs) has higher strength and wear resistance but poorer corrosion resistance. In the present investigation, the AlCoCrFeNi HEAs containing titanium(Ti) were fabricated via laser cladding to enhance the corrosion resistance properties of the coating and the influence of the Ti content on the microstructure of the coatings was investigated. The results show that the microstructure of the coating changed from a single BCC phase to a BCC+B2 phase with the addition of Ti. The Laves phases appeared within the coating when the Ti content was beyond 0.5 mol ratio. As an excellent corrosion-resistant element, Ti promoted the formation of a passive film and enhanced the corrosion resistance of the HEAs coating. The corrosion resistance of the coating first increased and then decreased with the addition of Ti, and the AlCoCrFeNiTi0.5 coating exhibited optimal corrosion resistance.

Influence of Ti element on the microstructure and crack of modulated WC-strengthened Ni-based alloy coatings by laser cladding

For laser cladding of WC reinforced Ni50A Ni-based alloy coatings can cause cracks and porosity. Cracks and pores will restrict the application and performance of the coating. In order to improve the crack condition of the coating, the influence of alloying element Ti on the crack was investigated by introducing it. Cracks in the coatings were eliminated. When the addition amount of Ti is 3wt%, the morphology and properties of the coating are the best. The phase composition, microstructure, elemental distribution and grain orientation of the coatings were characterised using X-ray Diffractometry (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectrometer (EDS), Electron Backscatter Diffraction (EBSD) and Transmission Electron Microscopy (TEM). The hardness and abrasion resistance of the coatings were tested using microhardness tester and friction tester. The results show that a large number of second phases are present in the coating when Ti particles are not added. The introduction of Ti element disperses the localised stresses in the Ni50A-WC coating. The macroscopic morphology of Ni50A-WC coating was improved. The introduction of Ti reduced the area of the second phase within the coating. The introduction of Ti generated TiC/TiWC2 in situ. However, the introduction of Ti increased the dilution rate and decreased the strength of the coating. Therefore, the microstructure of the coating can be controlled and the macroscopic defects of the coating can be improved by adjusting the addition ratio of Ti elements.

Development of the alternative technology of the plasma spray melting to plasma transferred arc method: Microstructure and mechanical properties of Ni20Cr coatings

Development of the alternative technology of the plasma spray melting to plasma transferred arc method: Microstructure and mechanical properties of Ni20Cr coatings

Nitrogen Pressure Significantly Impacts Microstructures and Mechanical Properties of CrAlN Coatings Prepared by Pulsed Laser Deposition

Nitrogen Pressure Significantly Impacts Microstructures and Mechanical Properties of CrAlN Coatings Prepared by Pulsed Laser Deposition

Microstructure and wear characteristics of austenitic stainless steel coatings fabricated through various directed energy deposition

Austenitic stainless steels are widely used in automotive and marine environments because of their high toughness, corrosion resistance, and wear resistance. The present comparative study focuses on the microstructure and wear resistance of double-layer austenitic stainless-steel coatings prepared on a ductile iron substrate using circular spot high-speed laser-directed energy deposition (DED) and broad-beam laser-DED. The results indicate that while the deposition process does not alter the physical phase of coating, it does influence the preferred orientation of surface grains. Both coatings exhibit characteristics of hypoeutectic alloys, where the harder eutectic structure serves as a skeleton to resist external pressure. The high-speed laser-DED coating demonstrates higher hardness and wears resistance due to its denser eutectic structure. In addition, its finer microstructure produces smaller wear debris, contributing to the formation of a denser oxide film, thereby enhancing wear resistance.

Thermal stability and microstructure of fluorine-free hydrophobic coatings of gas diffusion layers for fuel cell applications

Polytetrafluoroethylene (PTFE) is used as commercial hydrophobic treatment for gas diffusion layers (GDL) in polymer electrolyte fuel cells. This commercial hydrophobic treatment can reduce the electrical conductivity of GDLs and is facing an uncertain future due to the pending restriction of perfluoroalkyl substances (PFAS). Previously, we proposed surfactant doped polyaniline (PANI) coatings as a fluorine-free alternative hydrophobic treatment. Due to their anti-corrosion properties as well as the electrical conductivity, these coatings offer additional benefits for the GDL compared to PTFE. Prior work demonstrated improved maximum power of a low temperature polymer electrolyte fuel cell (LT-PEFC) using the PANI coated GDL compared to the commercial PTFE treated reference. Based on these findings, additional investigations are needed to optimize the coating and assess possible areas of applications. With this study, we propose the use of the coating in high temperature PEFCs due to its thermal stability determined via thermogravimetric analysis of polyaniline doped with different types of surfactants. A main focus of this work is the investigation of the uniformity and overall porosity of the polyaniline coatings on GDLs via µCT supported by deep learning. This analysis is complemented with fluid dynamics simulations to determine the tortuosity and the gas flow through the GDL. In the future, this approach could enable the optimization of the fluorine-free hydrophobic coatings in combination with the different layers of the membrane electrode assembly (MEA) such as the GDL and the catalyst layer to prevent mass transport limitations.

Structural Effects of Cold-Sprayed Ti Coating Modified with Ti-Based Satellite Particles with In Situ-Formed TiC

AbstractIn this paper, the influence of Ti-TiC satellite powder obtained in situ by the CVD method on the microstructure, properties, and residual stress of titanium cold-sprayed coatings was studied. A commercially available titanium powder was subjected to a satelliting process using the CVD process, where TiC particles were in situ formed on titanium granules. Then, a powder mixture of pure Ti and 20 wt.% of Ti-TiC satellite powder was obtained. Cold spray coatings of Ti-(Ti-TiC)sat powder mixtures were applied to Ti6Al4V substrates with carrier gas temperatures of 900 °C and 1100 °C. The coating characterization included microstructural analyses by SEM, hardness measurements, determination of Young’s modulus, phase composition by XRD, and residual stress measurements. Cross-sectional analysis revealed good cohesion between Ti and TiC during the satelliting process, which survives coating deposition. Moreover, the higher spraying temperature resulted in TiC crystallite size reduction, higher hardness, and Young’s modulus, decreasing linear and shear stresses.

Effect of ZrB2 on microstructure and wear properties of TC4 alloy coatings by laser direct energy deposition

In this paper, ZrB2/TC4 alloy coatings with different contents of ZrB2 were prepared on the surface of TC4 titanium alloy using laser direct energy deposition technology. The effects of ZrB2 content on the microstructure, phase, microhardness and friction and wear behaviors of the TC4 coating were investigated, and the enhancement mechanism of ZrB2 on the coating properties was analyzed. The results show that with the increase of ZrB2 content, the coating successively produces the white ring-like structure of the first and the last, the parallel structure of the fishbone and the staggered structure of the TiB compounds, and the microstructure of the coating is transformed from the elongated grains to the fine grains. The microhardness and wear rate of the 15 wt% ZrB2/TC4 coating reached up to 352.1HV and 5.9 × 10−6 g/N•m, respectively. Compared with the 100%TC4 coating, the microhardness is increased by 14.6 % and the wear rate is decreased by 52.0 %, indicating that the addition of ZrB2 was beneficial to improve the friction and wear properties of coating. Interestingly, when the content of ZrB2 reached 20 %, the brittleness of the coating was too high, leading to the phenomenon of grooves on the wear surface of the coating, and the wear rate was reduced by only 45.5 %.

Pore formation and pore inter-connectivity in plasma electrolytic oxidation coatings on aluminium alloy

The porosity and microstructure of plasma electrolytic oxidation (PEO) coatings are key factors in determining their properties and applications. Despite advances in understanding the PEO process, the mechanisms driving pore formation and their correlation with process parameters remain unclear due to the complex interplay between these variables. This study investigates the effects of treatment time and duty cycle on the microstructure of PEO coatings produced on an aluminium alloy in an alkaline electrolyte, with a particular focus on pore formation. Our findings reveal that longer treatment durations lead to the significant development of sub-surface pores at the interface between the inner and outer layers. Additionally, a lower duty cycle leads to an increase in sub-surface pores, while a higher duty cycle favours the formation of surface pores. Morphological, 3D microstructural mapping, and chemical analyses reveal that pore formation is driven by the micro-discharges, gas generation, and the preferred gas escape path within the micro-melt pools formed during the PEO formation process. The preferred gas escape path is closely linked to the characteristics and lifetime of local micro-melt pools, elucidating the mechanisms behind pore formation.

Study on the Effects of CeO2 on the Micro-Structure and Wear Resistance of CuCrZr Plasma Cladding Coatings

The electromagnetic railgun, a novel kinetic energy weapon, has found utility in military operations due to its enhanced safety features and superior precision. This study investigates the enhancement of wear resistance in CuCrZr rails through the plasma cladding of CuCrZr-CeO2 coatings with a varying Cerium dioxide (CeO2) content. To enhance the wear resistance of the CuCrZr track, plasma cladding of CuCrZr-CeO2 coatings with varying CeO2 content was investigated. The impact of CeO2 content (0%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%) on the microstructure, phase composition, and mechanical properties of the CuCrZr coating was assessed using scanning electron microscopy (SEM), X-ray diffraction (XRD), EDS(Energy Dispersive Spectrometer) surface scanning, friction and wear tests, and hardness analysis. The findings indicate that a CeO2 content of 0.15% leads to a transition in the coating’s microstructure from columnar to equiaxed crystals, with the densest grain structure. Beyond 0.15% CeO2, pore defects in the coating increase, compromising mechanical properties. The coating containing 0.15% CeO2 exhibits optimal performance, with a hardness of 75.3, representing a 5.31% increase compared to CeO2-free CuCrZr coatings. Under a 10 N load, the friction coefficient decreases by approximately 17.9% to about 0.64. Moreover, the minimum wear mass is reduced by 44.7% to 3.87 mg. The aforementioned research findings hold immense importance in extending the lifespan of the electromagnetic railgun and improving its operational efficiency.

Enhanced Surface Mechanical and Tribological Properties of H13 Die Steel with TiAlSiN Coating Deposited by HiPIMS

TiAlSiN is a potential protection coating for die steel to improve the surface hardness, anti-wear performance and suitability. In the present study, TiAlSiN is deposited on H13 die steel by high power impulse magnetron sputtering and the effects of bias voltage, deposition temperature, and film thickness on the performance of coatings are studied. The microstructure, mechanical and tribological properties of coatings are analyzed by energy dispersive spectrometer, X-ray diffraction, nanoindentation, friction and wear tests. The results show that with the changes of sputtering parameters, the content of Ti, Al, Si, and N fluctuates slightly. With the increase of bias voltage, deposition temperature and film thickness, the diffraction peaks of Ti3Al2N2 phase become wider. Higher bias voltage, deposition temperature, and film thickness are beneficial for obtaining coatings with high hardness, and strong wear resistance. By observing the surface morphology of coatings after grinding with Si3N4 balls, it was found that the wear mechanism of coatings contains abrasive wear, fatigue wear, and oxidative wear.

Microstructure and tribological properties of atmospheric plasma-sprayed TiO2 coatings reinforced by boron nitride nanosheets

ABSTRACT In this study, boron nitride nanosheets (BNNSs)/TiO2 composite coatings were fabricated using atmospheric plasma spraying. The phase composition and microstructure of composite coatings were characterized through X-ray diffraction (XRD) and scanning electron microscopy (SEM). Additionally, tribological tests were conducted using a ball-on-disc tribometer under dry sliding conditions. XRD analysis reveals the transformation of partial anatase TiO2 to rutile TiO2. SEM images demonstrate that the incorporation of BNNSs has no discernible impact on the coating’s morphology. The TiO2-BNNSs coating exhibited a reduction in both volume loss and wear rate by approximately 71.5% and 55.9%, respectively, in comparison to the TiO2 coating. The potential strengthening mechanisms of the composite coating are further discussed.

Effect of Dehydrogenation and Heat Treatments on the Microstructure and Tribological Behavior of Electroless Ni-P Nanocomposite Coatings

High phosphorus Ni-P coatings, both unreinforced and modified by the addition of alumina (Al2O3) and zirconia (ZrO2) nanoparticles, were manufactured by electroless deposition technique and heat-treated with different temperature and duration schedules. The effect of dehydrogenation (200 °C for 2 h) and its combination with crystallization heat treatment was studied in terms of microstructural changes and wear resistance. The amorphous structure of the coatings was not altered by the introduction of both Al2O3 and ZrO2 nanoparticles, and the addition of 1.5 g/L of ZrO2 yielded the highest microhardness due to better particles dispersion. Dehydrogenation improved hardness because of the early stages of grain growth; however, the greatest improvement in hardness (+120% compared to unreinforced Ni-P) was obtained after annealing at 400 °C for 1 h, because of the microprecipitation of the Ni3P crystalline phase induced by thermal treatment. No detectable differences in hardness and microstructure were detected when annealing at 400 °C for 1 h with or without prior dehydrogenation; however, the dehydrogenated coatings exhibited a lower Young’s modulus. ZrO2-reinforced coatings demonstrated improved wear resistance, and wear tests revealed that dehydrogenation is fundamental for lowering the coefficient of friction (−14%) and wear rate (−97%) when performed before annealing at 400 °C for 1 h. The analysis of the wear tracks showed that the non-dehydrogenated samples failed by complete coating delamination from the substrate, with abrasion identified as the predominant wear mechanism. Conversely, the dehydrogenated samples demonstrated better resistance due to the formation of a protective oxide layer, leading to an overall increase in the coating wear resistance.

Enhanced densification of TaC coating on graphite substrate via cobalt-assisted liquid phase sintering using wet powder process

In this work, tantalum carbide (TaC) coatings were prepared on graphite substrates using a wet powder forming and sintering process with the addition of cobalt (Co) as a sintering aid. The effects of cobalt content on the densification, phase composition, microstructure, and mechanical properties of the TaC coatings were investigated. The addition of a small amount of Co promoted the densification of the coating and enhanced its hardness and elastic modulus. At a Co content of 1.5 wt%, the coating exhibited a relative density of approximately 95.7 %, a hardness of 18.1 GPa, and an elastic modulus of 395.0 GPa. Morphological analysis revealed the densification mechanism of the coating during the high-temperature sintering process. Under the influence of the Co liquid phase, TaC particles rearranged and underwent dissolution-precipitation in the liquid phase, ultimately achieving densification of the coating.

Effect of Ni Enrichment on the Microstructure, Mechanical, and Tribological Properties of Hydrophobic Ni3Al Alloy Coatings

Effect of Ni Enrichment on the Microstructure, Mechanical, and Tribological Properties of Hydrophobic Ni3Al Alloy Coatings

Enhanced tribological performance of NiAl-based composite coatings: Design of the composition in coatings by addition of Mo and Nanodiamond

Nanodiamond/Mo reinforced in-situ synthesized NiAl-based composite coatings were prepared by laser cladding. The microstructure, microhardness, and tribological properties of these composite coatings were studied. The results show that the coating is mainly composed of NiAl and Ni3Al phases. ND and Mo show a synergistic effect, which not only reduces the porosity of the coating, refines the grain size, and also improves the microhardness. In addition, in the temperature range of 25–800 °C, they reduce the friction coefficient and wear rate of the coating. These findings provide a valuable reference for optimizing the performance of NiAl-based composite coatings.

Structural evolution and mechanical properties of Cr coatings deposited by magnetron sputtering on PCrNi1MoA steel

Cr coatings were prepared by direct current magnetron sputtering on PCrNi1MoA steel, a substrate that has received limited attention in previous studies. The influence of deposition temperature on the microstructure and mechanical properties of Cr coatings was clarified. A comparative analysis was also performed to assess their performance relative to Cr coatings on the stainless steel substrate. All coatings on PCrNi1MoA steel exhibited densely packed fibrous grains in the cross section and a faceted triangular pyramid shape on the surface. Generally, increasing the deposition temperature led to enhanced mechanical properties, primarily due to the reduction of flaws and microporosity, facilitated by the increased mobility of adatoms at higher temperatures. The maximum values of hardness (H), elastic modulus (E), ratios of H/E and H3/E2, and adhesion strength are 4.1 GPa, 117.8 GPa, 0.43, 0.45 GPa, and 27 N, respectively. Compared to the Cr coatings on stainless steel, those on PCrNi1MoA steel exhibited a higher (110) texture coefficient, more uniform grain structures at high deposition temperatures, smoother surfaces, and better adhesion to the substrate.

Mechanical, Tribological, and Corrosion Resistance Properties of (TiAlxCrNbY)Ny High-Entropy Coatings Synthesized Through Hybrid Reactive Magnetron Sputtering

This study investigates the effects of aluminum and nitrogen content on the microstructure, mechanical properties, and tribological performance of high-entropy coatings based on (TiCrAlxNbY)Ny systems. Using a hybrid magnetron sputtering technique, both metallic and nitride coatings were synthesized and evaluated. Increasing the aluminum concentration led to a transition from a crystalline to a nanocrystalline and nearly amorphous (NC/A) structure, with the TiAl0.5CrNbY sample (11.8% Al) exhibiting the best balance of hardness (6.8 GPa), elastic modulus (87.1 GPa), and coefficient of friction (0.64). The addition of nitrogen further enhanced these properties, transitioning the coatings to a denser fine-grained FCC structure. The HN2 sample (45.8% nitrogen) displayed the highest hardness (21.8 GPa) but increased brittleness, while the HN1 sample (32.9% nitrogen) provided an optimal balance of hardness (14.3 GPa), elastic modulus (127.5 GPa), coefficient of friction (0.60), and wear resistance (21.2 × 10−6 mm3/Nm). Electrochemical impedance spectroscopy revealed improved corrosion resistance for the HN1 sample due to its dense microstructure. Overall, the (TiAl0.5CrNbY)N0.5 coating achieved the best performance for friction applications, such as break and clutch systems, requiring high coefficients of friction, high wear resistance, and durability.

The Effect of Bi on the Kinetics of Growths, Microstructure and Corrosion Resistance of Hot-Dip Galvanized Coatings.

This paper presents the results of studies on the growth kinetics, microstructure (SEM/EDS) and corrosion behavior of coatings obtained by hot-dip galvanizing process in baths containing Bi additive. The coatings for testing were produced on low-silicon steel in a Zn bath containing 0.04, 0.12 and 0.4 wt.% Bi. The corrosion resistance of the coatings was determined comparatively in standard Neutral Salt Spray Tests (NSST) (ISO 9227) and sulfur dioxide test (SDT) in a humid atmosphere (ISO 22479). Potentiodynamic tests and electrochemical impedance spectroscopy measurements were conducted. It was found that the addition of 0.04 and 0.12 wt.% Bi reduces the total thickness of the coatings and the thickness of intermetallic layers, while the content of 0.4 wt.% Bi in the bath increases the thickness of the layers forming the coating. Direct corrosion tests (NSST and SDT) and electrochemical tests showed that the addition of Bi to the zinc bath reduces the corrosion resistance of the coatings. The corrosion resistance of the coatings decreases with increasing Bi concentration in the zinc bath. In the microstructure of the coatings, it was found that Bi precipitates mainly on the surface of the coating, but also on the cross-section of the outer layer and ζ intermetallic layer. Bi precipitates, due to their cathodic nature, affect the reduction of the corrosion resistance of the coatings with the increase of their content in the bath.