Showing papers in "Surface & Coatings Technology in 2022"
TL;DR: In this paper , a fluorine-free robust super-hydrophobic coating was fabricated on the Al alloy substrate by a simple and low-cost approach, where modified TiO2 nanoparticles were embedded onto a semi-cured epoxy resin adhesive layer.
Abstract: Here, a fluorine-free robust superhydrophobic coating was fabricated on the Al alloy substrate by a simple and low-cost approach. Embed modified TiO2 nanoparticles onto semi-cured epoxy resin adhesive layer prominently reduces the content of low-energy materials (stearic acid) on the superhydrophobic coating. This prepared coating with hierarchical structures, re-entrant structures and low surface energy shows superhydrophobic. The superhydrophobic coating shows excellent high impalement pressure even water droplets with the velocity of 3.43 m/s. This coating also exhibits stability after different tests and noticeable enhancement of adhesive strength compared with the coating without the epoxy resin. Moreover, this coating presents enhanced durability verified by a sandpaper abrasion and decreased friction coefficient by a wear test. It moreover enabled noticeable self-cleaning property. This superhydrophobic coating also shows promising anti-corrosion property in both the corrosion solution and the salt spray compared with the Al alloy substrate. Notably, the superhydrophobic property combined with photocatalytic function prominently improves the anti-biofouling property of the Al alloy substrate due to the superhydrophobicity reducing organic and bacterial adhesion and the photocatalysis providing organic degradation and preventing bacterial adhesion. The fluorine-free robust multifunctional coating with superhydrophobic and photocatalytic properties can be applied to functionalize various solid surfaces.
41 citations
TL;DR: In this paper , the Si-MoSi2 ceramic coatings were prepared on TZM alloy through a hot dip silicon-plating (HDS) process, and the results showed that the SiO2 protective film effectively inhibits the diffusion of oxygen and reduces the consumption rate of MoSi2 layer.
Abstract: The Si-MoSi2 ceramic coatings were prepared on TZM alloy through a hot dip silicon-plating (HDS) process. The hot dip experiments results showed that Si-MoSi2 ceramic coatings have a very dense surface morphology and low roughness (0.258 ± 0.009 to 0.347 ± 0.019 μm). The Si-MoSi2 ceramic coatings presents a typical layered structure with the outermost silicon-rich MoSi2 layer, the intermediate layer is the pure MoSi2 layer, and the Mo5Si3/Mo5Si3C diffusion layer between the MoSi2 layer and the TZM substrate. The oxidation tests showed that MoSi2 ceramic coating maintained a complete appearance after high temperature oxidation at 1500 °C for 4 h. The self-healing SiO2 protective film effectively inhibits the diffusion of oxygen and reduces the consumption rate of MoSi2 layer. HDS Si-MoSi2 ceramic coating presents a very excellent oxidation resistance at high temperature, which is mainly attributed to the uniform and dense coating structure and high surface silicon concentration.
40 citations
TL;DR: The limit of applicability of the correlation between the ratio of hardness to elastic modulus (H / E ) of coating systems and their wear resistance has been explored in this article .
Abstract: The limit of applicability of the correlation between the ratio of hardness to elastic modulus ( H / E ) of coating systems and their wear resistance has been explored. Experimental approaches to determine accurate H / E values by nanoindentation are discussed and best practice recommendations summarised. Small-scale tribo-testing has been used to simplify complex wear conditions, and the role of contact severity and damage tolerance studied to determine why and when coating optimisation strategies are effective. Case studies show the importance of relatively low coating elastic modulus in reducing tensile stresses in sliding/abrasive contact. This may be a key factor in why coating design for optimised H / E and resistance to plastic deformation , H 3 / E 2 , can be more effective than aiming for extremely high coating hardness since that is typically accompanied by high coating stiffness. The influence of substrate ductility and load support on the damage tolerance of the coating system in impact tests has been investigated by testing at different contact size. Results show that mechanical and microstructural factors should not be considered in isolation. The role of coating microstructural design and temperature on optimising coating performance in high speed machining is investigated.
31 citations
TL;DR: In this paper , the oxidation and tribological properties of CrMnFeCoNi/xTiC composite coatings produced by laser cladding were studied at 600 °C, and the addition of TiC to the coating promoted the oxidation process due to short-circuit diffusion.
Abstract: Extensive studies have been conducted on high entropy alloy composite coatings reinforced with micro-sized ceramic particles at the room-temperature. However, studies on their high temperatures properties are rare. The oxidation and tribological properties of CrMnFeCoNi/xTiC composite coatings produced by laser cladding were studied at 600 °C. The addition of TiC to the coating promoted the oxidation process due to “short-circuit diffusion”. During the high temperature wear process, brittle cracking did not occur on the worn surface, and a good wear-resistant intermediate layer was formed. The coatings exhibited low hardness, low wear rate, and high coefficient of friction due to the formation of composite oxide film formed on the worn surface with good adhesion to the matrix. • Tribology and oxidation behavior of CrMnFeCoNi coatings with different content of TiC • TiC in the coating forms a “short circuit diffusion” channel and promotes oxidation. • The ceramics in the composite coating played the load-bearing and load transfer role to improve the wear resistance.
31 citations
TL;DR: The concept of Si alloyed transition metal (TM) diborides was explored for bulk ceramics in this paper , where the authors studied the oxidation behavior up to 1200 °C for five different physical vapor deposited TM-Si-B2±z (TM = Ti, Cr, Hf, Ta, W) coatings.
Abstract: The concept of Si alloyed transition metal (TM) diborides – well explored for bulk ceramics – is studied for five different physical vapor deposited TM-Si-B2±z (TM = Ti, Cr, Hf, Ta, W) coatings, focusing on the oxidation behavior up to 1200 °C. In their as deposited state, all coatings exhibit single phased AlB2 prototype structures, whereby the addition of Si results in dense, refined morphologies with no additional phases visible in the X-ray diffractograms. With already low amounts of Si, the slope of the mass increase during dynamic oxidation flattens, especially for Ti-Si-B2±z, Cr-Si-B2±z, and Hf-Si-B2±z. Above distinct Si contents, the formation of a steady state region exhibiting no further mass increase is promoted (starting at around 1000 to 1100 °C). Best results are obtained for Hf0.21Si0.18B0.61 and Cr0.26Si0.16B0.58 (both around 2.4 μm thick in the as deposited sate), revealing drastically retarded oxidation kinetics forming 400 nm thin oxide scales after 3 h at 1200 °C in ambient air (significantly lower compared to bulk ceramics). This highly protective oxidation mechanism is attributed to the formation of an amorphous Si rich oxide scale. The Si content needed to form these oxide scales largely differs between the TM-Si-B2±z coatings investigated, also diversifying the prevalent oxidation mechanism, especially for Cr-Si-B2±z.
23 citations
TL;DR: In this article , three composite coatings were developed by varying Al2O3 particle sizes in micrometric, nano, and bimodal forms, and the results of the tests revealed that two of them successfully protect the underlying substrate owing to their hardness and fracture toughness which is higher than the other two.
Abstract: In the present experimental work, Inconel-625 (IN625) was reinforced with Al2O3 (30 wt%) to develop composite coatings with plasma spraying technique on ASTM SA210 GrA1 boiler steel. Three composite coatings were developed by varying Al2O3 particle sizes in micrometric, nano, and bimodal forms. The Inconel625 + 30 wt% micrometricAl2O3, Inconel625 + 30 wt% nano-Al2O3 and Inconel625 + 15 wt% micrometric Al2O3 + 15%nano-Al2O3 combinations were considered. The developed composite coatings were analyzed for the detailed microstructure studies, microhardness, fracture toughness, and elevated temperature erosion test. The elevated temperature erosion tests for bare substrate and coatings were conducted at 900 °C by using an erosion test rig (air jet) at two impingement angles 30° and 90°. By studying the eroded surfaces through scanning electron microscopy (SEM) micrographs, the mechanism of material removal was predicted. The existence of grooves and lips at a 30° and 90° impact angle on surfaces indicate the erosion mechanism consists of ploughing and micro-cutting action in the substrate. At 30° and 90° impact angles, all composite coatings exhibited a brittle erosion mode as erosion characteristics. The micrographs of eroded surfaces indicated splat removal, cracks, and fracture as the main erosion mechanism. The outcomes of the tests revealed that the bimodal composite coatings successfully protect the underlying substrate owing to their hardness and fracture toughness which is higher than the other two coatings. The better outcome of bimodal coatings was related to refined microstructures and good interaction among nano and micrometric Al2O3 reinforcement.
22 citations
TL;DR: In this paper , a survey of typical hard coatings belonging to the respective material classes, deposited by physical or chemical vapor deposition (PVD, CVD) on cutting tools to improve their application performance is presented.
Abstract: Since decades, protective hard coatings with thicknesses of a few micrometers are grown by physical or chemical vapor deposition (PVD, CVD) on cutting tools to improve their application performance. For the huge variety of cutting applications, different coating materials are used, which typically belong to the material classes of nitrides, carbides, carbonitrides, borides, boronitrides or oxides, frequently in bi- or multilayer stacks. The present work surveys typical hard coatings belonging to the respective material classes, deposited by PVD as well as CVD. Pioneering studies in this field as well as recent findings contributing to the establishment of comprehensive “synthesis – structure – property – application performance” relationships of the respective coatings are discussed and the current state-of-research is reviewed. Condensed summaries and comparisons between PVD and CVD coatings are given at the end of each subsection. In addition, current and future challenges for the hard coatings community are surveyed.
21 citations
TL;DR: In this paper , the effect of post-deposition annealing on CrN/CrAlN multilayer coating was evaluated using XRD, SEM, nanoindentation test, Rockwell-C adhesion measurements, and EIS assays.
Abstract: CrN/CrAlN multilayer coatings were deposited on AISI 304 stainless steel substrates utilizing the CAE-PVD process. Then the coatings were annealed at 400, 500, 600, and 700 °C for a duration of 1 h in a vacuum condition. The phases identification, surface morphology, mechanical properties, adhesion, and corrosion behavior of the coating before and after post-deposition annealing treatment were characterized using XRD, SEM, nanoindentation test, Rockwell-C adhesion measurements, and EIS assays, respectively. The results indicated that with increasing post-deposition annealing treatment temperature, the phase structures of the multilayer coating vary from a face-centered cubic CrN to a hexagonal Cr 2 N. Moreover, annealing resulted, in the decrease of the macroparticles on the coating surface decreased. The hardness of the multilayer coating decreased from 19 GPa to 17 GPa, which can be ascribed to the increase in crystallite size and the decrease in the residual stress and annihilation of defects as the temperature increased to 700 °C. Based on the EIS results, the sample annealed at 700 °C had the highest corrosion resistance among other samples, which can be attributed to a decrease in the porosities as corrosion initiation sites, the existence of Cr 2 N as corrosion resistance phase, and an increase in the crystallite size of the multilayer coating. • Comprehensive evaluation on the effect of annealing on CrN/CrAlN multilayer coating. • Significant decrease in residual stress and macrostrain. • Crystallite growth resulted in the decrease in the hardness of the coating by 10%. • Enhancement of electrochemical properties through post-deposition annealing.
20 citations
TL;DR: In this paper , a CO 2 laser polishing was used for surface modification of the additively manufactured (AM) Ti-6Al-4V grade 23 ELI, popular for medical devices and aerospace parts production.
Abstract: Poor surface quality of Additively Manufactured (AM) components, can greatly increase the overall cost and lead time of high-performance components. Examples are medical devices where surfaces may contact the patient's skin and hence need to be smooth and aerospace components with high fatigue strength requirements where surface roughness could reduce fatigue life. The average surface roughness (Ra) of AM parts can reach high levels greater than 50 μm and maximum distance between the high peaks and the low valleys of more than 300 μm. As such, there is a need for fast, cost effective and selective finishing methods of AM produced components targeted at high-performance industries. In this paper Ti-6Al-4V Grade 23 ELI, popular for medical devices and aerospace parts production, was L-PBF processed to manufacture parts which were subsequently treated via laser polishing. Here in this work, CO 2 laser polishing was used for the surface modification of the Ti-6Al-4V produced samples. The most significant processing parameters were optimised to achieve approximately an 80% reduction in the average surface roughness and a 90% reduction in the peak-to-valley distance with a processing time of 0.1 s/mm 2 and cost of 0.2 €/cm 2 . • CO 2 laser polishing of additively manufactured Ti-6Al-4V is presented. • Flat and cylindrical samples were successfully polished by using the methodology detailed in this article. • The percent overlap of the laser scanning track was an effective processing parameter to reduce surface roughness. • Double-pass lasing offered a further reduced surface roughness.
20 citations
TL;DR: In this article , Al2O3 particles reinforced FeCoNiCrMn HEA composite coatings were fabricated by cold spray and the microstructure, mechanical and tribological properties of the composites coating were studied.
Abstract: High entropy alloys (HEAs) are novel materials that have been extensively studied in recent years. In this work, Al2O3 particles reinforced FeCoNiCrMn HEA composite coatings were fabricated by cold spray. The microstructure, mechanical and tribological properties of the composites coating were studied and compared with those of the pure FeCoNiCrMn coating. The results indicate that cold spray is a promising process to fabricate HEA composite coatings. The composite coatings made in this work had higher hardness than pure FeCoNiCrMn coating due to the reinforcing effect of well distributed Al2O3 particles. The composite coatings also had improved wear-resistance properties with nearly 50% reduction in wear rate as compared to the pure FeCoNiCrMn coating. The improvement was due to the formation of tribo-layer which can effectively withstand material loss. The results also reveal that the main wear mechanisms for the composite coatings were dominated by adhesive wear in comparison to abrasive wear for the pure FeCoNiCrMn coating. This study proves the feasibility of cold spray for the fabrication of high-performance HEA composite coatings.
20 citations
TL;DR: A cross-scale study on the effect induced by laser shock peening (LSP) and physical vapor deposition (PVD) coating on the wear and corrosion resistance of FeCoCrNiAl high entropy alloys has been made in this article .
Abstract: A cross-scale study on the effect induced by laser shock peening (LSP) and physical vapor deposition (PVD) coating on the wear and corrosion resistance of FeCoCrNiAl high entropy alloys (HEA) has been made in this work. The nano scale FeCoCrNiAl HEA coating on substrate 304 steel and microscale FeCoCrNiAl HEA has been acquired through PVD nanocoating and LSP, respectively. The micro hardness, friction and corrosion properties have been investigated to evaluate the reliability of the material in application. The results of microhardness and wear test indicate that both approaches have increased the surface hardness of HEA through grain refinement. And the results for corrosion test reveal a competing effect between grain refinement and compressive stress. As the enhancement brought by PVD nano coating is not comparable to the cast sample, due to the side effect brought by grain refinement which will reduce the corrosion resistance. Surprisingly, specimens treated with LSP have better performance in corrosion resistance, as the compressive residual stress induced by LSP enhanced the adhesion between the substrate and modified layer, forming dense passive films to inhibit corrosion ions in the environment and successfully neutralized the side effect brought by grain refinement. Therefore, the modified layer induced by LSP on the surface contributes to the improvement of both wear resistance and corrosion resistance. • Effect of LSP and PVD on wear and corrosion resistance of HEA have been studied. • The wear and corrosion resistance of FeCoCrNiAl 0.1 are enhanced. • The grain refinement has a positive effect on the wear properties. • The compressive stress has a positive effect on the corrosion properties.
TL;DR: In this article , the effect and characteristics of the laser clad interstitial CoCrFeNi high entropy alloy coating reinforced with carbon nanotubes (CNTs) was investigated.
Abstract: In this study, the effect and characteristics of the laser clad interstitial CoCrFeNi high entropy alloy coating reinforced with carbon nanotubes (CNTs) was investigated. 1.0 wt% of CNTs were added as the reinforcement. To prepare composite powders before cladding, the CNTs and pre-alloyed CoCrFeNi powders were mechanically mixed without ball milling treatment. As a result, the microstructure of the CNTs on powder surface was well protected from serious damage. The effects of the CNTs upon the microstructure and wear behavior of the produced interstitial CoCrFeNi-CNTs coating were evaluated. The results showed that the intergranular (Fe, Cr) 7 C 3 /α eutectics were found to fully precipitate in the clad CoCrFeNi-CNTs coating. The hardness of the CoCrFeNi-CNTs coating was enhanced by 42.2% compared with that of the CoCrFeNi coating. The wear property was positively correlated with the hardness. The wear rate of the CoCrFeNi-CNTs coating (2.18 × 10 −5 mm 3 ·N −1 ·m −1 ) was significantly lower than that of the CoCrFeNi coating (10.54 × 10 −5 mm 3 ·N −1 ·m −1 ). The enhancements of the wear property originated from the solution strengthening of carbon on grains and the precipitation strengthening of (Fe, Cr) 7 C 3 carbides on grain boundaries. In wear process, the lamellar (Fe, Cr) 7 C 3 /α eutectics deposited on worn surface and eventually formed a carbide hardening layer structure and prevent severe wear on the CoCrFeNi-CNTs coating. • Mechanical mixing can avoid agglomeration of carbon nanotubes on powder surface. • Intergranular carbide eutectic precipitates with the addition of carbon nanotubes. • The carbide hardening layer is formed by carbide eutectic deposition in wear test. • Wear resistance of CoCrFeNi coating is enhanced by the carbide hardening layer.
TL;DR: In this article , an anti-icing surface with super-hydrophobic properties was designed by combining poly(methyl-3, 3,3-trifluoropropyl siloxane) (PMTFPS) modified silica with a low surface free energy fluorine-silicone resin.
Abstract: An anti-icing surface with superhydrophobic properties was designed by combining poly(methyl-3,3,3-trifluoropropyl siloxane) (PMTFPS) modified silica with a low surface free energy fluorine‑silicone resin. The hydrophobic silica particles were characterized using SEM, FTIR, and XPS. The hydrophobicity, wettability and wear resistance of the resulting coating were analyzed. The anti-icing and de-icing properties of the coatings were also characterized in terms of complete icing time and ice adhesion strength. The obtained SiO2-PMTFPS coating achieved a contact angle of 158.5° and a roll-off angle of 1°. Compared with tinplate sheets, icing time is delayed by 200% at −10 °C and 800% at −15 °C. Ice adhesion strength decreases by 91.8% compared with tinplate, making ice relatively easy to remove. After sandpaper abrasion and immersion in solutions with different pH and temperature, the coating is proven to exhibit good abrasion resistance and chemical durability in water solutions.
TL;DR: In this article , the authors used glow discharge optical emission spectroscopy, scanning electron microscopy, X-ray diffraction, transmission electron microscope, Xray photoelectron, and Raman spectroglobalization to evaluate the short-time oxidation resistance of coatings at temperatures of 1100, 1300, and 1500 °C.
Abstract: The Mo-Si-B, Mo-Zr-Si-B, and Mo-Hf-Si-B coatings were deposited by magnetron sputtering of the MoSi2-MoB, MoSi2-MoB-ZrB2 and MoSi2-MoB-HfB2 targets. The composition and structure of coatings were investigated by glow discharge optical emission spectroscopy, scanning electron microscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron and Raman spectroscopy. Mechanical properties were measured by nanoindentation method. The short-time oxidation resistance of coatings was evaluated at temperatures of 1100, 1300, and 1500 °C. The results showed that all coatings deposited onto alumina substrates were characterized by a dense columnar structure. Mo-Si-B coatings contained phases of hexagonal h-MoSi2 and amorphous a-MoB. With the addition of Zr and Hf, an increase in the lattice parameter and a decrease in the grain size of h-MoSi2 by 50 and 25%, respectively, were observed. The base Mo-Si-B coating had a high hardness of 30 GPa. The introduction of Zr and Hf led to a decrease in hardness by 24 and 20%, respectively. The Mo-Si-B coating was characterized by a minimal oxidation depth (<10 nm) at 1100 °C and 1300 °C, but a network of cracks that penetrated to the substrate was formed. Cracks on the surface of the Mo-Zr-Si-B and Mo-Hf-Si-B coatings were not observed; the formation of oxide layers, 0.3–2.0 μm thick, was revealed. The oxidation resistance of coatings at temperature of 1500 °C increased in direction Mo-Si-B → Mo-Hf-Si-B → Mo-Zr-Si-B. The best results for the Mo-Zr-Si-B coating were associated with a smaller grain size, higher thermal stability, and the formation of a protective layer based on SiO2 with the inclusion of ZrO2 crystallites.
TL;DR: In this paper , the effect and mechanism of ultrasonic vibration on the microstructure and performance of laser cladding 316L coating has been studied, providing a theoretical basis and technical support for the application of the ultrasonic-assisted laser cladd process.
Abstract: The effect and mechanism of ultrasonic vibration on the microstructure and performance of laser cladding 316L coating has been studied, providing a theoretical basis and technical support for the application of the ultrasonic-assisted laser cladding process. The results show that ultrasonic vibrations with different amplitudes can effectively improve the macroscopic forming quality of the cladding layer, among which the ultrasonic vibration with 17.5 μm amplitude is the best. Ultrasonic vibration can also significantly improve the micro-forming quality of the cladding layer, such as homogenizing the structure, refining grains and reducing porosity. The wear mechanism of the cladding layer with an ultrasonic assistance of 17.5 μm is mainly abrasive wear, so the wear resistance has been significantly improved. The ultrasonic-assisted cladding layer exhibits significant passivation behavior in 3.5 wt% NaCl solution. It may be that the surface roughness reduction and grain refinement caused by ultrasonic assistance can improve the integrity and compactness of the cladding layer, so the dynamic equilibrium process of the dissolution and reformation of the passive film is changed, which can improve the corrosion resistance of the surface. There are some equiaxed grains in the columnar-grains area of the ultrasonic-assisted cladding layer, mainly because the inside of some primary columnar grains has gone through a process of lattice distortion → dislocation multiplication → substructure rotation → formation of small-angle grain boundary → misorientation accumulation → formation of new grains in the process of ultrasonic-assisted laser cladding of 316L stainless steel.
TL;DR: In this paper , four different post-treatment methods including heat treatment, mechanical and chemical surface treatments as well as their combination were considered and their effect was studied on microstructure, surface, and mechanical properties of laser powder bed fusion (LPBF) V-notched AlSi10Mg samples.
Abstract: Complex geometries can be produced by laser powder bed fusion (LPBF) techniques in a layer-by-layer manner. These parts exhibit inhomogeneous microstructure and poor surface quality in their as-built state. Performing post-treatments to modify these imperfections can play a substantial role in enhancing the performance of LPBF parts. However, the effects of post treatments on local geometrical irregularities are not still well documented. In this study, four different post-treatments including heat treatment, mechanical and chemical surface treatments as well as their combination were considered. Their effect was studied on microstructure, surface, and mechanical properties of LPBF V-notched AlSi10Mg samples. The as-built samples were subjected to two different shot peening processes (using different Almen intensity, shot diameter, and shot hardness), chemical polishing and electro-chemical polishing, in individual and combined configurations. Comprehensive microstructural characterization was carried out and the surface state of the samples was studied in detail in terms of surface morphology and roughness. In addition, mechanical properties including microhardness and residual stresses were measured and finally the fatigue behaviors of the samples were analyzed and compared at a constant stress level. All post treatments led to improved fatigue life. The combination of the aforementioned post-treatments led to a remarkable fatigue life improvement up to 414 times higher compared to the as-built state.
TL;DR: In this article , laser cladding of vanadium carbide-reinforced Inconel 625 (In625) metal matrix composite (MMC) coating was carried out on grade 304 stainless steel substrates.
Abstract: In the present work, laser cladding of vanadium carbide (VC)-reinforced Inconel 625 (In625) metal matrix composite (MMC) coating was carried out on grade 304 stainless steel substrates. The microstructure, hardness, and abrasive wear performance were studied by changing the weight fraction of VC at 0, 5, 10, and 15 wt%, respectively. The effects of increasing the reinforcement phase on the microstructure evolution, composition, hardness, and abrasion resistance properties were evaluated on the obtained coatings. The results indicated the formation of defect-free coatings alongside the formation of secondary strengthening precipitates were observed within the primary γ-Ni matrix in the In625 clad. Complex secondary carbides were formed on all MMC coatings near the In625-VC interface region, indicating the formation of an interphase which guaranteed the bonding between the matrix and reinforcement. The results also showed an almost linear relationship between the amount of VC into the In625 alloy clads and the clads hardness. With a VC content of 15 wt%, the clads hardness increased approximately 65% with respect to a 100% In625 coating. On the other hand, while the addition of 5 wt% of VC slightly improves the abrasion resistance of the In625, further increased of the reinforcement phase content led to a reduction of the clads behaviour. • Vanadium carbide reinforced Inconel 625 coatings were deposited via laser cladding. • The higher the vanadium carbide content the higher the hardness of the clad. • The increase of reinforcement phase content led to a reduction of the clads abrasion resistance.
TL;DR: In this article , the effect of texturing, carburizing and their combination was investigated to improve the bonding strength of diamond-like carbon film (DLC) on Ti6Al4V alloy (TA) substrate.
Abstract: To improve the bonding strength of diamond-like carbon film (DLC) on Ti6Al4V alloy (TA) substrate, the effect of texturing, carburizing and their combination was investigated. The different surface treatments were carried out on the Ti6Al4V substrate surface by laser texturing and carburizing before the deposition of DLC coatings. Thus, three different DLC coated samples were prepared: 1. DLC coatings with a laser textured substrate, named TDLC; 2. DLC coatings with a laser carburized substrate, named CDLC; 3. DLC coatings with a hybrid laser textured and carburized substrate, named TCDLC. Meanwhile, the only mechanical polished DLC coatings (ODLC) were also prepared for comparison. The adhesion and tribological performance of different DLC coatings were evaluated by using variable depth nano-scratch tests and ball-on-disk wear tests . Among the four kinds of DLC coatings with different surface treatments, the bonding strength of hybrid pretreated coatings (TCDLC: 12.25 N) were highest compared with other three samples (ODLC: 5.73 N; TDLC: 8.72 N; CDLC: 9.28 N). The coupling of the mechanical-physical-chemical effects accompanying laser texturing and carburizing reaction can enhance the wettability and specific surface area of the Ti6Al4V substrate surface, thereby providing a mechanical self-locking and matching chemical property between the Ti6Al4V substrate and DLC coatings. • A hybrid pre-processing method of laser texturing and carburizing was proposed. • The combined treated DLC coated sample presented the best coatings adhesion. • Matching chemical property between Ti6Al4V substrate and DLC coatings was obtained.
TL;DR: In this article , laser-clad AlCrFeCoNi high entropy alloy (HEA) coatings, produced on the surface of AISI 316 L stainless steel, were pack-borided at 1000 °C for 4 h in open air, high-purity Ar and vacuum environments.
Abstract: Laser-clad AlCrFeCoNi high entropy alloy (HEA) coatings, produced on the surface of AISI 316 L stainless steel, were pack-borided at 1000 °C for 4 h in open air, high-purity Ar and vacuum environments. The HEA, which had an initial hardness of 6.14 ± 2.06 GPa, formed a complex boride layer consisting of (CoFe)B2, (CrFe)B2 and Cr2Ni3B6 phases on its surface, with hardness ranging from 15.95 ± 0.7 to 20.15 ± 4.50 GPa as a result of the boriding process. While the greatest boride layer thickness was obtained in the sample borided in vacuum, the highest surface hardness was obtained in the sample borided in air. The borided coatings showed improved wear resistance and lower friction values compared to the untreated control samples, both at 25 °C and 650 °C. The borided coatings also showed reduced coefficients of friction at 650 °C. The wear losses at 650 °C significantly exceeded those at 25 °C.
TL;DR: In this article , a liquid-fuelled high velocity oxy fuel (HVOF) thermal spray was used to sample the microstructure and mechanical properties of NiCrAlCY coatings and the results showed that higher oxygen flow rates are critical for obtaining coatings with lower porosity and higher microhardness.
Abstract: Nickel based superalloy are in demand for high temperature applications and their corrosion, erosion and wear resistance have been investigated for a long time. Nickel chromium (NiCr) alloys are widely used for corrosion resistant coatings, while chromium carbide nickel chromium (CrC-NiCr) alloys are preferred for wear resistant coatings at high temperature. In this study CrNiAlCY coatings were deposited via a liquid fuelled high velocity oxy fuel (HVOF) thermal spray using two spray parameters and tested as wear resistant coatings. Effects of processing parameters on microstructure and mechanical properties of the coatings were investigated. Results showed that higher oxygen flow rates are critical for obtaining coatings with lower porosity and higher microhardness. Coating with lower porosity and higher hardness was chosen for both room temperature (~24 °C) and high temperature (900 °C) unlubricated sliding wear tests in a ball on disc setup. The coating was tested against alumina counterbody under 3 different loading conditions (10, 30 and 60 N). The wear rate of the coating was directly proportional to the applied load at room temperature. In the room temperature tests, wear debris was produced, which then oxidised and pushed away to the edges of the wear track. On the other hand, wear debris was smeared on the wear surface at high temperature tests. The surface was oxidised into Cr 2 O 3 at high temperatures, which acted as a protective layer. Although thermal softening took place at higher temperatures, wear rates under 10 and 30 N were similar to room temperature values due to the protective oxide layer formed on the top surface; however, the oxide layer under 60 N could not withstand the load, started to crack and lost its protective ability. • CrNiAlCY coatings have been produced using a liquid-fuelled HVOF thermal spray. • Effects of spray parameters on the microstructure and hardness studied. • Wear performance was investigated against the alumina counter body. • 2 Different temperature settings were used during the wear tests.
TL;DR: In this article , a super-hydrophobic micro-nano structured composite coating on the E40 low-temperature steel was designed and fabricated, which was composed of an underlying WO3 coating derived from the pulsed electrodeposition process and a top polytetrafluoroethylene (PTFE) layer obtained from the magnetron sputtering.
Abstract: The fabrication of superhydrophobic coatings on the low-temperature steels has rarely been explored to this day. Herein, we designed and fabricated a superhydrophobic micro-nano structured composite coating on the E40 low-temperature steel, which was composed of an underlying WO3 coating derived from the pulsed electrodeposition process and a top polytetrafluoroethylene (PTFE) layer obtained from the magnetron sputtering. The synergistic effect of the hierarchical micro-/nanostructures of the WO3 coating and the low surface free energy of the fluorine-containing PTFE layer makes the PTFE/WO3 coating superhydrophobic, which demonstrated a water contact angle of 159° and a water roll-off angle of ≤1°. The PTFE/WO3 coating exhibited outstanding anti-pollution properties towards both the solid pollutant such as carbon black particles and the liquid pollutant such as black ink. Importantly, the PTFE/WO3 coating demonstrated excellent anti-icing properties with low icing temperature and small ice-adhesion strength, while simultaneously possessing outstanding anti-fouling performance. The present work provides a new strategy for fabricating coatings with multifunctionality on metallic materials which can work under low-temperature and biofouling conditions.
TL;DR: In this paper , AA 7075-T6 aluminum alloys were treated by different shot peening processes, and the surface characteristic, including refined microstructure, residual stress and surface roughness, were characterized, then its effect on localized corrosion pitting and stress crack propagation behavior were investigated.
Abstract: Shot peening is often reported as being beneficial to stress corrosion cracking resistance; however, the increased surface roughness induced by shot peening may promote localized corrosion pitting. Here, AA 7075-T6 aluminum alloys were treated by different shot peening processes, and the surface characteristic, including refined microstructure, residual stress and surface roughness, were characterized, then its effect on localized corrosion pitting and stress crack propagation behavior were investigated. Compared with single shot peening, the microstructure refinement was not further enhanced by dual shot peening with adding a subsequent low intensity of micro-shot peening. The surface residual stress distribution become more uniform, and the average surface residual stress value was increased from −158 MPa to −175 MPa. The maximum residual stress was synchronously increased from −302 MPa to −319 MPa. Meanwhile, the surface roughness (Ra) value was decreased from 4.05 μm to 2.05 μm. Compared with single shot peening, the degree of surface localized corrosion pitting was alleviated after dual shot peening due to its low surface roughness and more uniform compressive residual stress distribution. The depth of stress corrosion cracking for dual shot peening was decreased with a minimum value of 33 μm, which may be ascribed to the high maximum compressive residual stress at the subsurface.
TL;DR: In this paper , the synergic effect of cavitation erosion (CE) and corrosion on two HVOF-sprayed nickel-based cermet coatings, WC-10Ni5Cr (WC-NiCr) and WC-18Hastelloy C(WC-H), on Monel K-500 substrate was evaluated.
Abstract: Monel K-500 is a nickel-based alloy that is a widely used material in industries like hydraulic, chemical and marine. In its marine application, such as in seawater, Monel alloy suffers from high cavitation and corrosion. In one of the approaches to control these degradations, thermal spray coatings are recommended to enhance the resistance against these degradations. The current study assesses the synergic effect of cavitation erosion (CE) and corrosion on two HVOF-sprayed nickel-based cermet coatings, WC-10Ni5Cr (WC-NiCr) and WC-18Hastelloy C (WC-H), on Monel K-500 substrate. CE tests were conducted for 15 h in a corrosive (3.5% NaCl) environment. It was observed that WC-NiCr coating reduced the CE losses in Monel alloy by 45%. In pure cavitation (DI water) conditions, the better CE of a coating originates from its better combination of microhardness and indentation toughness. Whereas, in a corrosive medium, the CE behavior of a coating depends upon its electrochemical properties too. Electrochemical corrosion test on both the coatings revealed that WC-NiCr coating had better corrosion results than that of WC-H coating due to its higher corrosion potential (Ecorr) value and slightly lower corrosion current density which may influence the CE performance of the investigated coatings. In-depth study of the erosion mechanism for each of the coatings was conducted using Scanning Electron Microscopy (SEM). It was observed that due to the effect of the corrosive medium, several pits and pores were generated over the coating surface. These defects provided additional nucleation sites for CE in the coatings resulting in a high level of erosion losses in the coatings. Considering the effects of cavitation and corrosion simultaneously, HVOF-sprayed WC-NiCr coating is recommended to enhance the cavitation-corrosion resistance in Monel K-500 alloy.
TL;DR: In this paper , acid pickling, grinding and anodising treatments were applied to the Ti-6Al-4V titanium substrates, and the CFRPs were grinded to compare the performances.
Abstract: Adhesive bonding between carbon fibre reinforced polymer (CFRP) and titanium alloy is extensively employed to achieve lightweight and adequate strength in aircraft structures. In this study, acid pickling, grinding and anodising treatments were applied to the Ti-6Al-4V titanium substrates, and the CFRPs were grinded to compare the performances. A special technique named resin pre-coating (RPC) was also used to improve substrate wetting. The single lap shear tests results showed that the bond strengths of grinded and anodised specimens were higher than that of the acid pickled specimens. The RPC treatment further increased the bond strengths of all the specimens by 29.9%–51.5% and appeared to be more effective on rough surfaces. A combination of the NaOH anodising and RPC treatment yielded the highest bond strength of 22.0 MPa, which was 105.3% and 70.1% higher than the bond strengths of acid pickled and grinded specimens, respectively, and the failure mode changed from adhesive failure to CFRP delamination failure. These surface treatments are simple and thus suitable for aerospace and aviation industries.
TL;DR: In this article , CoNiCrAIY metallic bond coatings were coated on Inconel 718 super alloy using a high velocity oxygen-fuel (HVOF) deposition technique.
Abstract: Thermal barrier coatings (TBCs) are protective coating systems that are mostly utilized to improve the thermal insulation and functional performance of gas turbine engines and other aircraft components that are both stable and movable. These coatings protect materials operating in harsh conditions from structural damage caused by corrosion, oxidation, the CaO-MgO-Al 2 O 3 -SiO 2 effect (CMAS), thermal shock , volcanic ash, and vermiculite deposits at high temperatures. In this study, CoNiCrAIY metallic bond coatings were coated on Inconel 718 super alloy using a high velocity oxygen-fuel (HVOF) deposition technique. Then, single YSZ, Gd 2 Zr 2 O 7 (GZ), and double YSZ/GZ based ceramic topcoats were applied to the bond coats by using the electron beam physical vapor deposition (EB-PVD) method. The produced TBC samples and the uncoated Inconel 718 superalloy substrate were subjected to vermiculite (VM) deposition at 1250 °C for 4 h, and then the coatings were characterized. To determine the phase structures, microstructural and mechanical properties of the TBCs, X-ray diffractometer (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer elemental mapping analysis (EDS), stereo microscopy analyses, porosity, and hardness measurements were used. The obtained results were comparatively evaluated with the recent related studies in the literature. • The aim of this study is to investigate the VM behavior of innovative single- and double-layer TBC systems. • The VM infiltration has occurred through the surface of the Inconel 718 superalloy substrate and all other TBC systems. • HVOF-bond coating and EB-PVD GZ coating were used for deposition of the TBCs. • On the Inconel 718 super alloy surface, YSZ, Gd 2 Zr 2 O 7 , and YSZ/Gd 2 Zr 2 O 7 coatings were deposited. • The TBC systems' initial porosity percentages decreased, but the top coating hardnesses increased. • The TGO structure formed at the interface with the effect of high temperature.
TL;DR: In this paper , a well-known hard material (VC) has been explored as potential candidate for surface modifications to overcome the problem of cavitation erosion (CE) in hydro machinery components.
Abstract: A well-known hard material (VC) has not been explored as potential candidate for surface modifications to overcome the problem of cavitation erosion (CE) in hydro machinery components. Therefore, in this course of work, VC has been blended with a malleable and soft binder material (CuNi-Cr) in three different proportions (VC, VC + 50%CuNi-Cr, and CuNi-Cr) and coated over SS316 steel with the help of HVOF spraying system. It has been observed that with the increase in VC content in the candidate coatings, the hardness, porosity, and thickness increased. CE tests were carried out with the help of an in-house fabricated cavitation erosion apparatus as per ASTM G134 Standard. The CE resistance of SS316 steel was found to be enhanced with the application of HVOF sprayed VC and CuNi-Cr based coatings. HVOF coating prepared with 100% VC content have showed excellent wear resistive properties owing to its maximum hardness (1023 HV 9.81N ) and better rebounding properties due to maximum thickness and porosity. CE parameters consisting of highest velocity of jet, intermediate stand-off distance (SOD) and normal impedance were found to be dominating to produce maximum cavitation erosion. Moreover, SS316 steel have showed ductile mode of failure with signatures of material removal as overlapped CE pits and plastic deformation sites. However, the mode of failure for coatings have been changed from ductile to brittle with the increase in VC content in the coating matrix with signatures changes from plastic deformation to cracks and pores in case of CuNi-Cr and VC coatings, respectively. • VC and CuNi-Cr composite coatings have been efficaciously prepared using HVOF spray process. • Microhardness of coatings was reported to be increased with increase in VC content. • Erosion resistance of SS316 steel was found to be significantly improved after deposition of coatings. • Mode of failure for coatings have been changed from ductile to brittle with the increase in VC content.
TL;DR: In this article , a single-layer Cr (8 um) and multilayer Cr(8 μm)/Mo (3 μm) coatings were deposited by magnetron sputtering.
Abstract: The oxidation and interdiffusion behavior of Cr- and Cr/Mo-coated Zr1Nb zirconium alloy were investigated. A single-layer Cr (8 um) and multilayer Cr (8 μm)/Mo (3 μm) coatings were deposited by magnetron sputtering. The coated Zr1Nb alloy samples were oxidized in air at 1100 °C for 15–60 min. Both coating types had a protective scale during high-temperature (HT) oxidation. The use of Mo sublayer resulted in preventing CrZr interdiffusion under high temperature. Scanning electron microscopy, optical microscopy, X-ray diffraction before and after HT oxidation and in situ X-ray diffraction up to 1250 °C were used to identify interdiffusion behavior of the system of Cr/Mo/Zr. Some aspects of applying of Cr/Mo coatings for Zr nuclear fuel claddings are discussed.
TL;DR: In this article , Ni-doped Al2O3 nanocomposite ceramic coatings were produced on Cp-Ti samples at two different rotational speeds by the spin coating process, which is a sol-gel method.
Abstract: Cp-Ti is frequently used in biomedical applications because of its good corrosion and high biocompatible properties. However, its poor wear resistance limits its use in some applications. Therefore, this study aims to improve its wear and corrosion resistance by producing Ni-doped Al2O3 nanocomposite coatings on Cp-Ti. In order to achieve this goal, undoped Al2O3 and Ni-doped Al2O3 nanocomposite ceramic coatings were produced on Cp-Ti samples at two different rotational speeds by the spin coating process, which is a sol-gel method. Afterward, their structural and morphological features were examined by XRD, SEM, Raman, and 3D surface profilometer. Reciprocating wear tests and electrochemical investigations were performed to determine their wear and corrosion properties.
TL;DR: In this paper , the effect of bilayer thickness and the individual sublayer thickness ratio on the microstructure and mechanical properties of ZrN/TiN multilayer coatings was investigated.
Abstract: Modifying the architecture of multilayer hard coatings allows to adjust the mechanical properties of these materials for a given application. Within this work, the effect of the bilayer thickness (Λ) and the individual sublayer thickness ratio on the microstructure and mechanical properties of ZrN/TiN multilayer coatings was investigated. Multilayer coatings with Λ of 570, 320 and 35 nm were deposited by cathodic arc evaporation and compared to TiN and ZrN single-layer coatings. The microstructure was investigated by X-ray diffraction (XRD) and scanning electron microscopy. All coatings exhibit a single phase face-centred cubic structure and a predominant (111) texture. A columnar structure was observed for all coatings and grain growth extending beyond the ZrN/TiN interfaces was evident in all multilayers. For all coatings, compressive residual stresses were determined by XRD using the sin 2 ψ method, where the multilayer sample with the largest Λ exhibited the highest compressive residual stress of −1.7 ± 0.2 GPa. Lower compressive residual stresses could be correlated with decreasing Λ and decreasing ZrN:TiN thickness ratio. Nanoindentation experiments as well as micro-mechanical bending tests were conducted to assess the mechanical properties of the coatings. The ZrN/TiN multilayer sample with Λ of 35 nm showed the highest hardness of 28.0 ± 1.1 GPa. This value is similar to the TiN single-layer and higher compared to the ZrN single-layer, which exhibited a hardness of 27.9 ± 1.4 GPa and 25.8 ± 1.3 GPa, respectively. While the ZrN single-layer showed the highest fracture toughness, the ZrN/TiN multilayer samples were identified as the mechanically stiffest and strongest of the investigated coatings, since they exhibited a higher fracture stress compared to the single-layer coatings. The obtained results allow to optimise the architecture of ZrN/TiN multilayer coatings yielding the desired coating properties for application in the cutting industry. • Arc evaporated ZrN/TiN multilayer coatings with varying bilayer thickness Λ • Smaller Λ leads to grain refinement and more pronounced (111) texture. • Multilayer coating with lowest Λ exhibits the highest hardness. • Highest fracture toughness for ZrN single-layer coating • Improved fracture stress for multilayers compared to single-layers
TL;DR: In this article , a superhydrophobic nickel-phosphorus/nickel/fluorinated polysiloxane (PFDTMS) triple-layer composite coating was successfully designed and fabricated on AZ31 magnesium alloy.
Abstract: To improve the corrosion protection of a nickel-based coating to the underlying magnesium alloy, a superhydrophobic nickel‑phosphorus/nickel/fluorinated polysiloxane (PFDTMS) triple-layer composite coating was successfully designed and fabricated on AZ31 magnesium alloy. The composite coating consists of an electroless-deposited nickel‑phosphorus (ELNi) bottom layer, an electrochemically deposited nickel (ECNi) nano-cone array middle layer, and a PFDTMS top layer via a dehydration-condensation reaction of silane. The surface morphology, structure, and chemical composition of the coating are identified by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The static water contact angle (WCA) of the composite coating is 153.0° ± 4.6°, attributed to the synergistic effect between nano-cone-shaped nickel and PFDTMS layer. Compared to the untreated magnesium alloy, the corrosion current density of the coating decreases by four orders of magnitude based on the Tafel curve, and the corresponding impedance modulus at low frequency (|Z|ƒ=0.01 Hz) increases by almost four orders of magnitude based on the electrochemical impedance spectra (EIS), demonstrating the superior corrosion protection to magnesium alloy. Lastly, the wetting states of the water droplets on the nickel‑phosphorus layer with and without electrodeposition of nickel nano-cone array and silane modification are also discussed in detail.