Adhesion Strength Of Coatings Research Articles

Effect of Transition Metals Oxide Additives on the Properties of Mixed-Alkali Glass for Electric Insulating Coatings on Aluminum

In order to reduce the cost of the thick-film technology of microcircuits and heating elements, as well as to expand its areas of use, it became necessary to expand the range of materials that, along with ceramics and steel, can also be used as substrates for these products. One of these advanced materials is aluminum. Electrically insulated coatings on metals are subjected to repeated heating and cooling while their produce and use, which promotes the creation of temperature stresses in the coating and leads to their chipping. Therefore, in order to improve the water resistance and adhesion strength of electrical insulation coatings on aluminum, CuO, ZrO2 and Bi2O3 additives were examined. There was found an increase in water resistance with a simultaneous increase in the adhesion strength of the enamel coating with an aluminum substrate with the addition of not more than 3 pts. wt. of copper oxide (II), up to 1 pts. wt. of zirconium oxide (IV), and up to 4 pts. wt. of bismuth oxide (III) w.r.t. 100 pts. wt. of glass.

THE EFFECT OF TiN, TiAlN, CrAlN, AND TiAlN/TiSiN COATINGS ON THE WEAR PROPERTIES OF AISI H13 STEEL AT ROOM TEMPERATURE

TiN, TiAlN, CrAlN and TiAlN/TiSiN films were deposited on AISI H13 hot work steel substrate by cathodic arc evaporation method. Each coating was optimized in laboratory conditions and the highest hardness and wear resistance coatings were taken into consideration for this study. Morphological properties, chemical compositions, crystallographic structure, nano hardness and adhesion strength of coatings were analyzed with SEM, AFM, EDS, XRD, nano indentation and scratch resistance tester. Wear experiments were performed using ball-on-disk tribometer against Al2O3 ball of 6[Formula: see text]mm diameter and wear volume of coatings were measured using optical profilometer. Wear experimental results revealed that all coated samples showed higher wear resistance and hardness than uncoated AISI H13 steel substrate. The highest wear and scratch resistances as well as nano hardness were attained for CrAlN coating. TiAlN coating has the lowest scratch resistance and wear resistance. Adhesive wear mechanism was the dominant wear mechanism for CrAlN coatings which is the highest wear resistant coating. Abrasive wear mechanism was the dominant wear mechanism for TiAlN coatings which is the lowest wear resistant coating.

Effects of constituent layers and interfaces on the mechanical and tribological properties of metal (Cr, Zr)/ceramic (CrN, ZrN) multilayer systems

The influences of constituent layers and interfaces on the mechanical and tribological behaviors of metal (Cr, Zr)/ceramic (CrN, ZrN) multilayer coatings were systematically investigated in the present study. Four sets of multilayer coatings (Cr/CrN, Cr/ZrN, Zr/CrN and Zr/ZrN) with the same number of interfaces were synthesized by multi-arc ion plating technique. The crystalline structures of the multilayer coatings were determined by X-ray diffraction and morphologies were observed by scanning electron microscope and transmission electron microscope. Furthermore, the nanoindenter, Vicker indenter, scratch tester and ball-on-disk tribometer were employed to evaluate the hardness, indentation toughness, adhesion strength and tribological properties of as-prepared coatings, respectively. Results revealed that the multilayer coatings with different constitute layers and interfaces presented different microstructures and properties. Based on the analysis of the cross-sectional indentation topographies, Zr interlayers exhibited higher crack resistances compared to Cr interlayers. Zr/CrN multilayer coating showed the highest hardness of 28 GPa, the strongest strength adhesion (>100 N) and the lowest wear rate. The excellent tribological performance of Zr/CrN multilayer coating was mainly ascribed to the high crack resistance of Zr layer, high wear-resistant layer of CrN as well as the local coherent interface between Zr and CrN sublayers.

(Cr/TiAlCrN/TiAlN/AlSiN/AlSiO) Multi Layer Solar Selective Coatings for Concentrated Solar Power Plant

A multi layer solar selective coating Cr/TiAlCrN/TiAlN/AlSiN/AlSiO gives the good absorption (α= 0.95) and low emission (Є= 0.08) over the SS 316 tube for solar thermal applications. In this multi layer solar selective coating each layer has unique properties that mostly depend upon the each layer thickness. Individual layer thickness has been optimized to get high absorbance (α= 0.95) and low emission (Є= 0.08). metal nitride multilayer films display a unique combination of exceptional properties with respect to optical absorption, thermal emission, corrosion resistance, adhesion between coating and surface and thermal stability at high temperatures. The sequence of the Cr/TiAlCrN/TiAlN/AlSiN/AlSiO coating layers was selected based on their relative thickness, which was optimized to get good solar selectivity (α/Є). The multilayer solar selective coating was characterized by using Raman spectrometer, Ultra violet- VisibleNIR spectrophotometer, Scanning electron microscope (SEM), Transmission electron microscopy (TEM) etc. Scratch test was used to find the coating adhesion strength and corrosion tests were also done for these absorber coatings.

Developments in pre- and post-treatment of thin films and their influences on surface topography and coating adhesion strength of cutting tools

Due to the increased requirements on machining of metallic and non-metallic materials, the pre- and post-treatment of hard thin films has been an important topic in several researches in the past decade. The main improvement in tool properties by a reduction of surface inhomogeneities is reached by an additional mechanical or chemical treatment before and/or after the coating process. Especially the cleaning before coating has to be considered to reduce the amount of debris of the pre-treatment which may negatively effect surface quality after the coating process. The mainly used processes of mechanical treatment to enhance surface topography before and after coating are several machining processes such as abrasive jet machining or drag finishing. This paper introduces a novel process for the pre- and post-treatment of coated cutting tools by elastically bonded diamond grinding wheels. Both the removal rate of surface inhomogeneities, the influence of surface topography before and after coating and the influence of the initial tool surfaces regarding coating adhesion strength were investigated to underline the potential of this pre- and post-treatment. Additionally, a new method for characterizing and describing the number of coating defects and proportion area of coating defects per $${\hbox {mm}}^{2}$$ is presented.

Computer-aided detection of the optimal spraying modes of coatings based on intermetallic titanium-aluminum alloys

The computational experiments results on simulation of a layered structure formation and the prediction of characteristics (porosity, roughness, adhesion) of metallic coatings based on intermetallic titanium-aluminum alloys (α2-Ti3Al, γ-TiAl and TiAl3) are given. The coatings under conditions typical of atmospheric plasma spraying (APS) and for high-velocity spraying (HVOF, D-Gun Spraying, etc.) by computer-aided design have been prepared. The ranges of the “key physical parameters (KPPs)” values of the sprayed particles, which ensure the stable formation of spreading and solidified melt particles (splats) on the sprayed surface for each of the three types of intermetallic titanium-aluminum coatings, have been detected. Taking into account the stable splat formation conditions, as well as the minimum of porosity (and roughness) and the maximum adhesion strength of the simulated coatings, the optimal spraying modes of coatings based on intermetallic titanium-aluminum alloys (Ti3Al, TiAl and TiAl3) were determined.

Wear-resistant Ti–Al–Ni–C–N coatings produced by magnetron sputtering of SHS-targets in the DC and HIPIMS modes

The hard wear-resistant nanocomposite Ti–Al–Ni–C–N coatings were deposited by direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HIPIMS) in the Ar, Ar+15%N2, and Ar+25%N2 atmospheres. The structure of coatings was analyzed using the X-ray diffraction analysis, glow discharge optical emission spectroscopy, and scanning electron microscopy. Mechanical and tribological properties were measured using the nanoindentation and scratch testing as well as by tribological testing using the “pin-on-disc” scheme. Electrochemical corrosion resistance and oxidation resistance of coatings were investigated. The results suggest that the coatings are based on the FCC phases TiCN and Ni3Al with crystallites size ~3 and ~15 nm, correspondingly. DCMS coatings with optimal composition were characterized by hardness 34 GPa, stable friction coefficient <0.26 and wear rate <5 × 10-6 mm3N-1m-1. Application of HIPIMS mode allowed the increase of adhesion strength, tribological properties and corrosion resistance of coatings.

Electrophoretic deposition of hydroxyapatite coating on biodegradable Mg–4Zn–4Sn–0.6Ca–0.5Mn alloy

ABSTRACT Aluminium-free Mg–4Zn–4Sn–0.6Ca–0.5Mn alloys, with similar mechanical properties to natural bone, were produced and used as substrates for electrophoretic deposition (EPD) of hydroxyapatite (HA) powder. HA powder was deposited at three levels of DC voltage (50, 100 and 150 V) at different times. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used for phase characterization. Cavities appeared in coated specimens with a coating thickness of more than 70 µm and micro-cracks appeared in a coating thickness of more than 100 µm. The maximum adhesion strength of coatings was 2.8 ± 1.1 MPa for 150 V–5 s. Electrochemical impedance spectroscopy (EIS) test showed that coating resistance and charge transfer resistance increased in the coated samples of 100 V–5 s and 150 V–5 s, respectively.

Cold Spray Technology to Promote Conductivity of Short Carbon Fiber Reinforced Polyether-Ether-Ketone (PEEK)

Recent studies showed that cold spray is a suitable way to produce metallic coatings on non-metallic surfaces such as polymers and composites for engineering applications. Mechanical bonding and particle anchoring process onto these substrates have not been totally understood yet. This study is focused on the creation of conductive coatings by cold spray onto short carbon fiber reinforced PEEK. For the requirements of the industrial application, the deposit should be able to tolerate both electrostatic and electric currents (higher than 10A). Because of their high conductivity, aluminium and copper powder seemed to be the best candidate materials. To promote adhesion and coating build up, copper-zinc and copper-PEEK mixed powders were also tested. A correlation between experimental and numerical tests has been adopted to assess and improve the possibilities of this material coupling. Both low pressure and high-pressure cold spray equipment were used for the spraying. Since polymer matrix-based composites are thermosensitive materials, it was necessary to develop a computational fluid-dynamics tool to investigate the interaction of the hot gas on the substrate and the correlation with the deposition process. A series of finite element simulations of single and multi-particle impacts onto local structures of the composite, as observed from SEM images of the specimens, is on-going. A classical pull-off test of the specimen will be adopted to collect data about coating adhesion strength. Finally, the four points measurement by Van der Pauw method will be used to assess the conductivity of specimens for different powders and coating thicknesses.

Properties of the protective powder coating made on the basis of nickel and received by the cold spray method

The structure, porosity, microhardness, adhesion strength of gasdynamic powder coatings have been investigated. Patterns of the process of electrochemical breakdown and passivation of coatings have been studied during comparative tests in the seawater in accordance with time factors. It is established that the protective coating on the basis of nickel with increased thickness in combination with low apparent porosity and high adhesion strength provides reliable electrochemical protection of the electric contacts made of titanic VT3-1 alloy in the sea water.

Investigation of Properties of Electro-metallized Coatings Deposited by Supersonic Air Stream with Aerosol Fluxing

The article presents the results of studies of the effect of flux components on the adhesive strength, porosity and oil absorption of coatings obtained by supersonic arc metallization (EM) using aerosol fluxing (AF) deposited on 45G2 steel with a speed v = 400-410 m / s. Due to the use of AF in EM, the adhesion strength of electrometallization coatings (EM coatings) increases. The highest value of adhesive strength is 66 MPa. Porosity due to the use of AF decreases by 1.5 - 1.6 times, in comparison with EM coatings without AF. At the same time, the oil absorption of EM coatings using AF decreases 1.6–1.7 times. It is advisable to use EM coatings with AF when restoring worn-out parts for various purpose equipment, as well as for eliminating defects at the production stage.

Effect of microwave heating on microstructure and elevated temperature adhesive wear behavior of HVOF deposited CoMoCrSi-Cr3C2 coating

This research reports the improvement of high-temperature sliding wear resistance of a grade 15 titanium alloy protected by an HVOF sprayed CoMoCrSi-Cr3C2 coating. The coatings have been tested in as-sprayed condition and after a post-deposition microwave heating step. The powder feedstock has been manufactured by high energy ball milling. X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) equipped with the Energy Dispersive Spectroscopy (EDS) methods were used for coatings characterization. Surface roughness, microhardness, adhesion strength, and porosity of coatings were also measured. The wear test was conducted at an applied load of l0 N and 20 N with varying temperatures of 200 °C, 400 °C, and 600 °C under dry sliding conditions. Co3Mo2Si, Co7Mo6, Mo3Si, Co3Mo, and Co2Mo3 were the intermetallic laves phases generated in the CoMoCrSi feedstock during HEBM process. The microwave-fused coating exhibited metallurgical bonding, homogeneous structure, less porosity, and greater hardness as compared to as-sprayed coating. Microwave-treated coating revealed better wear property than an as-sprayed coating. This was mainly due to the intermetallic formation and metallurgical bonding in coatings. The fused coatings exhibit tribo-oxide layers during sliding action which was the main phenomenon of improving the wear resistance of the fused composite coatings.

Stability and osteogenic potential evaluation of micro-patterned titania mesoporous-nanotube structures.

Background: Although titanium dioxide nanotubes (TNTs) had great potential to promote osteogenesis, their weak bonding strength with titanium substrates greatly limited their clinical application.Purpose: The objective of this study was to maintain porosity and improve the stability of TNT coatings by preparing some micro-patterned mesoporous/nanotube (MP/TNT) structures via a photolithography-assisted anodization technology.Methods: The adhesion strength of different coatings was studied by ultrasonic cleaning machine and scratch tester. The early adhesion, spreading, proliferation and differentiation of MC3T3-E1 cells on different substrates were investigated in vitro by fluorescent staining, CCK8, alkaline phosphatase activity, mineralization and polymerase chain reaction assays, respectively.Results: Results of ultrasonic and scratch assays showed that the stability of TNTs (especially 125 nm) was significantly improved after being patterned with MP structures. In vitro cell assays further demonstrated that the insertion of MP structure into 125 nm TNT coating, which was denoted as MP125, could effectively improve the early adhesion, spreading and proliferation of surface MC3T3-E1 cells without damaging their osteogenic differentiation.Conclusion: We determined that the MP/TNT patterned samples (especially MP125) have excellent stability and osteogenesis properties, and may have better clinical application prospects.

Adhesion strength of flame sprayed ceramic coatings obtained by robotic projection

Introduction: One of the possible applications of ceramic thermal barriers is in shells (permanent moulds – die casting). The moulds` capacity to support very high temperatures (up to 1600 °C) plays a crucial role in the selection of materials due to the liquid state of the cast iron. Objectives: This paper presents and discusses the obtained results from robotic flame projection tests, carried out with the purpose to quantify the influence of several factors of flame sprayed in the adhesion strength of coatings of Nickel-Aluminium-Molybdenum and Zirconium Oxide. In literature a minimum adhesion strength was not found for the application of thermal ceramic barriers in the coating of permanent casting moulds, so in this work it is intended to obtain its values ​​considering several combinations of projection parameters and substrates. Methods: The determination of the adhesion strength was performed according to the standard ASTM C633-79 where the coated test specimens were glued to CK45 steel against-specimens with a cyanoacrylate glue (LOCTITE 415). A weight of 100 N was then applied for 3 minutes to promote the initiation of the polymerization reaction of the cyanoacrylates and a period of 24 hours was needed so the bonded glue could acquire its maximum strength (sufficient enough to tear off the coating of the specimen). Finally tensile tests were carried out at the speed of 1 mm/min. Results: The main parameters studied are the material of the substrate, the projection angle and the substrate preheating temperature. The higher adhesion strength for the sprayed to 90° (average value of 6.2 MPa) was obtained by the specimens of spheroidal graphite cast iron (SGCI) with a preheating temperature of 120 °C. For the preheating of 90 °C and spray angle of 90° the aluminum-copper (AlCu) and brass specimens were the ones that obtained the higher adhesion strengths (average value of 4.5 MPa). The sprayed of 65° originates the higher adhesion strength in all the materials used for the substrate, being the highest value (average value of 8.3 MPa) obtained by the spheroidal graphite cast iron. Conclusions: The results obtained clearly suggest that the substrate material and the preheating temperature strongly influence the adhesion strength. The analysis of the coatings microstructures, using optical microscopy, supports this observation.

Biomechanical compatibility and electrochemical stability of HA/Ta2O5 nanocomposite coating produced by electrophoretic deposition on superelastic NiTi alloy

In this paper, natural hydroxyapatite (nHA) and nHA/20 wt% Ta2O5 coatings were electrophoretically deposited on NiTi. Phase analysis and microstructural characterizations of coatings were accomplished using X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM). Micro-indentation examination results revealed that nHA/Ta2O5 coating has the most compliant elastic modulus (32.85 GPa) to that of the adjacent bone tissue. Adhesion strength of coatings that was determined with tensile as well as nano-scratch tests affirmed the better adhesion properties of nHA/Ta2O5 compared with nHA coating on NiTi. Fracture toughness calculations from nano-scratch data exhibited the highest value for nHA/Ta2O5 coating (1 MPa m1/2). Degradation behaviors of nHA and nHA/Ta2O5 coated NiTi in Phosphate Buffered Saline (PBS) solution were characterized by electrochemical impedance spectroscopy (EIS) technique during 30 days of immersion. Time-dependent evolution of open circuit potentials and impedance characteristics' results clarified the positive role of Ta2O5. Reasons for this improvement were explained by the lower amounts of open porosities and easier blocking of pores in the presence of Ta2O5.

Influence of plasma spraying parameters on microstructure and corrosion resistance of Cr3C2-25NiCr cermet carbide coating

PurposeIn this work, Cr3C2-25NiCr coatings were deposited on 410 stainless steel substrate by using the atmospheric plasma spray technique, at varying spaying parameters. The porosity and microhardness, adhesion strength and corrosion behaviour of coatings were examined in relation to these spraying parameters.Design/methodology/approachThe microstructure of prepared coatings was examined by using scanning electron microscopy. The coating compositional analysis was performed by using X-ray diffraction (XRD) technique. The corrosion resistance of coated steel was investigated by potentiodynamic polarization. Results indicate that optimal factors for minimalizing the porosity were as follows: 10 g/min feed rate, 600 A plasma current and 100 mm spraying distance. The spraying factors influencing corrosion resistance of coating were also evaluated.FindingsUnder this optimal condition, the porosity of coating reached its minimal value of 3.1 per cent. The microhardness and adhesion of coatings also reached their maximum values of 64.8 Rockwell Hardness scale C and 60 MPa, respectively. XRD results indicated the transformation of Cr3C2originating from Cr3C2-25NiCr source powder into Cr7C3and Cr23C6crystalline phases, due to the high temperature during spraying process. The undetectable Cr3C2peaks indicating that this phase was remained in coating at very low concentrations. The potentiodynamic polarization and salt spray tests confirmed the highest corrosion resistance for the coating prepared by optimal spraying parameters.Originality/valueThe application of Cr3C2-NiCr cermet carbit coating for protection of steel from corrosion-erosion is very promising.

Surface roughening of Al2O3/Al2O3-ceramic matrix composites by nanosecond laser ablation prior to thermal spraying

Al2O3/Al2O3 ceramic matrix composites are candidate materials for high-temperature applications such as gas turbines. As water vapor corrosion of Al2O3/Al2O3-CMC (ceramic matrix composite) is a major issue, the application of suitable environmental barrier coatings is inevitable. An important factor for coating adhesion, especially in thermal spraying, is mechanical interlocking. Therefore, a rough substrate surface is needed. Although it has been proven that laser ablation is a suitable method for surface preparation of metallic substrates, no studies on Al2O3/Al2O3-CMCs are available. Therefore, the suitability of surface preparation of an Al2O3/Al2O3-CMC by laser ablation for use prior to atmospheric plasma spraying was examined. The laser ablation threshold fluence for Al2O3/Al2O3-CMC was determined. The effects of different processing parameters on the surface were studied. Various surface morphologies were obtained, such as cauliflower and honeycomb structures. The samples were characterized by white light interferometry, laser microscopy, and scanning electron microscopy. The obtained surface structures were coated with Gd2Zr2O7. It was found that the adhesion strength of coatings on laser treated samples was drastically increased.

Approaches to Increasing the Adhesion Strength of Hard Wear-Resistant Nanostructured Coatings Based on the Ti–B–(Cr, Si, C)–N System

The structure and properties of Ti–B–N, Ti–Cr–B–N and Ti–Si–B–C–N coatings, deposited by magnetron sputtering are investigated. Various approaches to increasing adhesion strength are considered: deposition of sublayers, application of a high bias voltage at the beginning of deposition, preliminary ion etching of a substrate, and implantation by high-energy ions at various stages of deposition. Scratch testing is used to evaluate coating adhesion.

New insight into the loss of adhesion of ZnMg[sbnd]Zn bi-layered coatings on steel substrates

In this research, physically vapor deposited MgZn and ZnMgZn bi-layered coatings were annealed at 180 °C for different annealing times to study the origin of the adhesion loss during heat treatment. In the case of MgZn bi-layered coatings, it was observed that MgZn2 and Mg2Zn11 intermetallics are formed during annealing from Zn and Mg by diffusion, which results in a reduction of the thickness of the initial pure zinc interlayer. In the case of ZnMgZn bi-layered coating, the “interfacial adhesion strength” at the ZnMg/Zn interface was quantified by using scratch test. The novel finding is that the adhesion strength of as-deposited coatings at the interface of ZnMg/Zn is independent of the thickness of the zinc interlayer (tZn). tZn decreases gradually during annealing at 180 °C. The “adhesion performance” of the studied coatings, as tested by BMW crash adhesion test (BMW AA-M223), drops drastically when tZn is less than a threshold (~ 500 nm). The obtained results indicate that tZn plays the significant role in the adhesion performance of ZnMgZn bi-layered coatings.

Titania nanotube interface to increase adhesion strength of hydroxyapatite sol-gel coatings on Ti-6Al-4V for orthopedic applications

Sol-gel coating hydroxyapatite (HA) allows for non-line-of-sight coatings on metallic implants that enhance biocompatibility and osseointegration, but coatings are on the order of a few microns thick and have poor adhesion, especially at low sintering temperatures; Both issues can limit implant longevity. In order to improve coating adhesion strength, a titania nanotube interface was used to reduce thermal mismatch and provide a nano-scale surface morphology for mechanical interlocking, while multiple dip-coatings achieved coating thicknesses >70 μm. In this study, Ti-6Al-4V disks were anodized to produce self-assembled titania (TiO2) nanotubes (NTs) on the surface of the substrates, while HA sol-gel was used to dip-coat the samples. The titania layers measured 800–900 nm thick, with nanotube pore widths of 90 ± 12 nm. Pure HA coating thicknesses were measured at 73.3 ± 10.5 μm and 84.97 ± 18.1 μm for polished Ti-6Al-4 V and anodized Ti-6Al-4V, respectively. The adhesion strengths of pure HA coatings on anodized (NT) surfaces were significantly higher (P < 0.05, N = 7) than polished surfaces at 19.02 ± 3.36 MPa and 13.8 ± 3.28, respectively. Strontium was doped into sol-gel coatings (Sr-Sol) to enhance bioactivity and showed a significant increase in preosteoblast MTT optical density after 3 days of culture compared to pure HA sol-gel, and plasma sprayed pure HA and strontium-HA (Sr-HA). SEM imaging showed well attached osteoblast cells with a similar morphology of multiple, long filopodia across all samples. This study shows that forming titania nanotubes through anodization is a viable approach to increase the adhesion strength of sol-gel coatings sintered at low temperatures, and demonstrates a facile method to incorporate dopants that enhance the osteoconductivity of HA sol-gels.