Surface Roughness Of Coatings Research Articles

Structural and mechanical properties of Si-doped CrN coatings deposited by magnetron sputtering technique

This study successfully deposited Si-doped CrN coatings onto Si (100) substrate by direct current magnetron sputtering. The concentration of Si in the CrSiN coatings was varied by changing the Si target current during deposition. The microstructural and mechanical properties were determined by employing X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy, and nanoindentation test. According to the results, the coating with 3.3 at.% Si contents (CrSiN-2) show an increase and decrease in the crystallite size and coating surface roughness, respectively, leading to solid solution hardening with an optimum hardness and elastic modulus of 21.37 GPa and 205.68 GPa, respectively. With continued Si addition, the coating roughness increased and the mechanical properties gradually decreased and attained 184.08 GPa and 18.95 GPa for the elastic modulus and hardness of the coating with a maximum Si concentration of 9.2 at.% (CrSiN-5).

Evaluation of Some Composite Paint Coatings’ Appearance Quality Using Fractal Dimension

Composite materials are characterized by multiple layers, which leads to a complexity in the design in order to ensure the effective operation of the constituent elements. This article provides information on the use of fractal dimension in assessing the quality of the appearance of paint coatings. The scientific originality of the article lies in the establishment of a correlation between the surface roughness of coatings, the quality grade of their appearance and fractal dimension. As a result, a model of the length of the coating surface profile, with the fractal dimension D, was proposed. The practical significance lies in the proposal to evaluate the quality of the surface of paint and varnish coatings in terms of fractal dimension. An increase in the surface roughness of the coating, a decrease in the appearance quality grade and an increase in the fractal dimension have been observed. Numerical values of the index of the fractal dimension of the coating surface profile, which depended on the porosity of the substrate, have been obtained. The influence of the filling of the paint composition on the quality of the appearance of the coatings has been estimated. It has been revealed that there was an increase in the surface tension of the paint composition, a decrease in the quality of the appearance of the resulting coating and an increase in the roughness and fractal dimension of the coating surface. The influence of the method of applying the paint composition and the preparation of the base surface on the quality of the appearance of the coatings are considered. The results obtained can be applied in various types of production to improve the quality of paint coatings.

Assessment of the effect of surface roughness on electrochemical characteristics of AZ80 magnesium alloy treated by PEO

The main purpose of this article, is to provide the evaluation of the influence of selected pre-treatment method, mainly grinding by various emery papers, which were used before the plasma electrolytic oxidation (PEO) process to assess the electrochemical characteristics of AZ80 magnesium alloy in 0.1 M NaCl solution. Moreover, the exposure time of the PEO pretreatment was set on 14 min. Subsequently, the surface roughness of PEO coatings was analyzed by confocal microscope. In the next step, electrochemical characteristics of ground surfaces with prepared PEO coatings were determined by the potentiodynamic polarization (PDP) at the laboratory temperature.

Evaluation of Novel Chitosan Based Composites Coating on Wettability for Pure Titanium Implants

This work aims to prepare chitosan (CS)-based coated layers, CS (10 wt% nanosilver/90 wt% CS, 10 wt% biotin/90 wt% CS, and 5 wt% nanosilver–5 wt% biotin)/90 wt% CS coatings are prepared, onto pure Ti substrate. The surface morphology of the novel CS composite coating was studied using field emission scanning electron microscopy, atomic force microscopy (AFM), Fourier transforms infrared (FTIR) and wettability test. Results show that the addition of (biotin, nanosilver) 5 Vol.% improves the properties of composite materials. Using different particles’ scale size aid in improving the combinations in the alginate, producing a dual effect on film properties. Coating surface roughness decreased in the chitosan-based biocomposite with preferable homogeneity and crack-free coating layers, as confirmed by AFM. An increase in surface roughness ensured substitution, which enhanced the surface structures. The high wettability of the CS-based coating layers was due to the presence of nanoparticles, and the composite coatings with CS, nanosilver, or biotin had excellent wettability because of the good hydrophilic nature of the CS matrix combined with reinforced particles. The FTIR results showed that peaks of the blending of CS plus nanoparticles, CS plus biotin, or CS plus nanosilver plus biotin were excellent matching with no changes in the structure of the matrix.

Effectiveness and safety of bleaching agents on lithium disilicate glass ceramics.

Aesthetic expectations have increased the use of aesthetic materials in dentistry. Lithium disilicates are frequently used materials for these expectations. Bleaching is another method used to provide aesthetics. Bleaching processes on restorative materials are not fully known. This study investigated the effect of at-home and in-office bleaching methods on the color change, surface roughness, and topography of lithium disilicate glass-ceramic materials produced with two different techniques and subjected to different polishing procedures. A total of 144 disc-shaped pressed and computer-aided design (CAD) lithium disilicate glass-ceramic specimens were randomly divided into four groups. Glazing and three different chair-side polishing procedures were performed. The specimens in each group were randomly divided into two groups and subjected to at-home and in-office bleaching processes (n=9). The home bleaching process was repeated with 16% carbamide peroxide agent for six hours for seven days, while the in-office bleaching process was applied with 40% hydrogen peroxide agent for two sessions of 20 minutes. After the bleaching processes, the final color and surface roughness experiments of the specimens were carried out, and the results were recorded. ANOVA and Tukey multiple comparison tests were used FOR the statistical analysis of the data (α=0.05). The material*polish*bleaching, polish*bleaching, material*bleaching, and material*polishing interactions were not statistically significant regarding color and roughness changes of both specimens (P>0.05). Both bleaching processes can be safely applied to lithium disilicate glass-ceramic materials.

Solving the Bonding Problem of the Ni Thin Coating with the Ultrasonic Assisted Electrochemical Potential Activation Method.

Electroplating nanocrystallite Ni coating can improve the mechanical properties of the metal structure surface, which is widely used in fabricating metal MEMS devices. Because of the large internal compressive stress caused by the oxidation layer of the substrate surface, the Ni coating easily falls off from the substrate surface. To solve this bonding problem, the ultrasonic assisted electrochemical potential activation method was applied. The ultrasonic experiments have been carried out. The bonding strength was measured by the indentation method. The substrate surface oxygen element was tested by the X-ray photoelectron spectroscopy (XPS) method. The dislocation was observed by the TEM method. The compressive stress was tested by the XRD method. The coating surface roughness Ra was investigated by the contact profilometer method. The results indicated that the ultrasonic activation method can remove the oxygen content of the substrate surface and reduce the dislocation density of the electroplating Ni coating. Then, the compressive stress of the electroplated Ni coating has been reduced and the bonding strength has been improved. From the viewpoint of the compressive stress caused by the oxygen element of the substrate surface, mechanisms of the ultrasonic activation method to improve the bonding strength were researched originally. This work may contribute to enhancing the interfacial bonding strength of metal MEMS devices.

Fabrication of negative carbon superhydrophobic self-cleaning concrete coating: High added-value utilization of recycled powders

In this work, two cost-effective methods for preparing negative carbon superhydrophobic self-cleaning concrete coatings were developed by using silane-modified recycled powders (RP) from concrete and carbonated & silane-modified RP. The effects of silane-modification and carbonation on RP, the surface roughness and performances of RP coatings were investigated. The results showed that both methods achieved negative carbon emission. RP and carbonated RP were successfully modified by silane, and two possible silane modification mechanisms corresponding to the two methods were proposed. Surface rough structures of the two coatings were formed by the stacking of powders on the surface of cement paste, which both exhibited excellent superhydrophobicity. In addition, both coatings presented desirable mechanical properties, weathering resistance and chemical stabilities in performances tests. These two high added-value utilization methods of RP are considered to be of great significance to low-carbon city construction and green economic development.

Pulse Electrodeposited Super-Hydrophobic Ni-Co/WS2 Nanocomposite Coatings with Enhanced Corrosion-Resistance

The hydrophobicity and corrosion resistance of composite coatings can be effectively improved by changing the electrodeposition method and adding inorganic nanoparticles. In this work, the incorporation of WS2 nanoparticles significantly increased the surface roughness of Ni-Co coatings. The best hydrophobicity and corrosion resistance of the Ni-Co/WS2 nanocomposite coatings (water contact angle of 144.7°) were obtained in the direct current electrodeposition mode when the current density was 3 A/dm2 and the electrodeposition time was 50 min. Compared with direct current electrodeposition, the pulsed current electrodeposition method was more conducive to improving the electrodeposition performance of the nanocomposite coatings. Under the conditions of a current density of 3 A/dm2, pulse duty cycle of 70%, and pulse frequency of 1000 Hz, the nanocomposite coatings reached a superhydrophobic state (water contact angle of 153.8°). The nanocomposite coatings had a slower corrosion rate and larger impedance modulus in this state, and thus the corrosion resistance was superior. The wetting state of the Ni-Co/WS2 nanocomposite coating surface was closer to the Cassie–Baxter model. The protective air layer formed by the layered rough microstructures significantly reduced the actual contact area between the liquid and the substrate, achieving excellent hydrophobic and corrosion resistance properties.

Experimental and theoretical analyses of material removal in poppet valve magnetorheological finishing

Poppet valves used in internal combustion engines have a high risk of failure due to significant temperature and pressure. These poppet valves need surface finishing at the nano-scale level to prolong their life during their working use. In the present research, the chosen poppet valve has narrow ridge profiles, which is difficult to nano-finish by conventional processes due to certain limitations. The magnetorheological fluid-based finishing method can be effectively used for this kind of complicated narrow profile. For the magnetorheological fluid-based finishing processing of the poppet valve, a novel magnet fixture and setup is used. For checking the efficiency of this setup, surface characterization and surface roughness for polished and unpolished surfaces are outlined using a field-emission scanning electron microscope, microscope and optical profilometer. The final surface roughness of Sa = 23.1 nm at poppet profiles were obtained. All manufacturing defects like burrs, dents, scratches and pits are almost removed. The study of finishing forces in the magnetorheological fluid-based finishing method is also carried out using magnetostatic fluid–solid interaction, experimental and theoretical analysis. This force analysis supports the development of the material dislodgement model to anticipate material removal rate while finishing. The gap (error = 12.87%) between the experimental and theoretical material removal rate is marginal. It has high accuracy and reliability for specific applications.

Surface quality optimization of laser cladding based on surface response and genetic neural network model

The model was established to optimize the laser cladding process parameters, the coating surface topography can be predicted and controlled. Taguchi and Box-Behnken (BBD) experiments were used to carry out the experimental design of laser cladding multi-channel lap. 316 L stainless steel coating was cladded on the surface of 45 steel substrate. The genetic algorithm-back propagation (GA-BP) neural network and response surface methodology (RSM) models were established respectively. The prediction accuracy of the two models was compared. The coupling effect between cladding process and multi-channel lap forming quality was analyzed. The relationship between cladding process parameters, such as laser power, feeding speed, scanning speed and overlap ratio, and surface roughness of coating was studied. The experimental results show that: The root mean square error (RMSE) and absolute mean deviation (AAD) of the GA-BP model are smaller than those of the RSM model. The coefficient of determination R2 of the GA-BP model is closer to 1 than that of the RSM model. The minimum roughness predicted by GA-BP model is 20.89 μm, which is lower than that of RSM model (35.67 μm). The final findings: in the optimization of process parameters of laser cladding, overlap ratio and scanning speed has significant effects on coating surface roughness. The GA-BP model of the coating surface roughness prediction accuracy is better than the RSM model. The prediction and control of the coating surface roughness are realized by GA-BP model, for the precise forming of the laser cladding coating surface, which provides theoretical basis and technological direction.

Femtosecond laser polishing of additively manufactured parts at grazing incidence

Surface polishing is usually a requisite for making additively manufactured (AM) parts ready for practical applications. Due to its advantages of being flexible and noncontact, laser polishing has attracted increasing research interest. In this research, femtosecond (fs) laser polishing was established to post-process both the top surfaces and sidewalls of AM parts. The challenge to remove three levels of roughness (i.e., the initial surface roughness of the AM parts, the undulations newly introduced during fs laser polishing, and the micro-nanoscale surface features induced by fs laser irradiation) was identified and addressed. Mirror surfaces with Sa < 200 nm were achieved on stainless steel parts printed with an initial roughness >20 µm. Both parallel- and perpendicular-incidence were investigated for the polishing, with the former verified to be more effective in eliminating the initial roughness of the AM parts, due to the elongated focal intensity profile of a Gaussian beam irradiated on the AM part surfaces. The challenge of forming three-zone surfaces during the parallel-incidence was further addressed through a grazing-incidence polishing approach, and uniform smooth surfaces were realized. Fine-tuning the laser power enabled controlling the submicron surface features formed under fs laser irradiation, which determined the final achievable surface roughness.

Preparation of Ni-Cu composite coatings with excellent tribological property and corrosion resistance by doping OH-BN(h)-PA-Zn-DCD hybrid

In this study, a novel Ni-Cu/OH-BN(h)-PA-Zn-DCD composite coatings with excellent wear resistance and corrosion resistance was developed, which may be used in the field of seawater corrosion. By the self-assembling of phytic acid, Zn2+ and dicyandiamide to grow PA-Zn-DCD structure onto the surface of hydroxylated BN(h) nanosheets, obtained a hybrid denoted as OH-BN(h)-PA-Zn-DCD, which was doped into Ni-Cu coating by pulse electrodeposition. The results show that OH-BN(h) and OH-BN(h)-PA-Zn-DCD hybrids affect the surface morphology, roughness, microcrystals size and thickness of the composite coatings. Simultaneously, compared with NC coating and NC/HB-1.5 coating, NC/BP-1.5 coating has the highest microhardness (559.26 Hv), the lowest friction coefficient (0.172), and the best corrosion resistance (icorr is 3.551 × 10−8 A·cm−2, Rct is 1.098 × 106 Ω·cm2). In addition, the EIS results of the immersed specimens showed that the NC/BP-1.5 composite coating still has good protective ability after soaking for 15 days in simulated seawater medium (Rct is 7.434 × 106 Ω·cm2).

Investigation of electrochemical discharge machining process variables during µ - drilling on stir casted novel Zn/ (Ag+ Fe)-MMC for biomedical applications

ABSTRACT Stainless steel, titanium alloy, and cobalt have long-term risks when used as metallic implants. Zinc is essential component of human body and can be used for metallic implants. The research presents the fabrication of novel hybrid Zn/(Ag + Fe)-MMC using stir casting method, analysis of microstructural and mechanical properties of fabricated MMC specimen. Electrochemical Discharge Machining (ECDM) was employed for the µ-drilling on the fabricated MMC. The effect of ECDM process variables like supply voltage, peak current, pulse-on-time, pulse-off-time, feed rate and electrolyte concentration on material removal rate (MRR), overcut (OC) and tool wear (TW) were identified during µ-drilling. Experiments had been performed based on the one factor-at-a-time approach. From the experiments it was found that MRR, OC and TW increase as supply voltage, peak current, pulse-on-time, electrolyte concentration increase and decrease as pulse-off-time increases. An increment in feed rate increases the MRR and TW but overcut decreases. Scanning electron microscopy (SEM) analysis at maximum MRR condition shows rough surface finish and ovality in µ-drilled hole. Whereas high circularity and uniform drilling attributes were obtained along the whole depth at minimum OC condition.

A review on the influence of process variables on the surface roughness of Ti-6Al-4V by electron beam powder bed fusion

Electron beam powder bed fusion (EB-PBF) has been given much attention in recent years for its potential in the aerospace and medical industries, particularly with Ti‐6Al‐4V. However, these processes produce parts with inherent rough surface finishes, impacting the performance and generating additional challenges and costs with surface post-processing. This review examines the primary mechanisms responsible for surface roughness generation in EB-PBF and the process variables that have been verified to influence the surface quality of Ti‐6Al‐4V parts. The challenges in surface metrology of metallic PBF parts are also discussed, as are new perspectives and guidelines for future research.

Effect of the Addition of Shellac Self-Healing and Discoloration Microcapsules on the Performance of Coatings Applied on Ebiara Solid Board

Self-made shellac microcapsules and discoloration microcapsules in different proportions were added to water-based coatings and the influence of different proportions of self-healing discoloration microcapsules on the coating performance for Ebiara solid boards was discussed. Through a three-factor, two-level orthogonal experiment, the effects of the content of the addition of discoloration microcapsules, shellac microcapsules, and microcapsules on the performance of the coating were explored; the most influential factor of microcapsules was the shellac microcapsule content. Through the coating repair experiment, after 5 days of repair, the coating without adding shellac microcapsules does not display the repair effect. When the shellac microcapsules and discoloration microcapsules were added simultaneously, the width of the coating decreased by 3–6 μm after 5 days of repair, displaying a good repair effect. The shellac microcapsules have a great influence on the surface roughness of coatings. After adding the shellac and discoloration microcapsules, the hardness of the coating was not significantly affected. It was found that there was no chemical reaction between the coating and microcapsules. The best comprehensive performance was obtained by adding 15.0% shellac microcapsules in primer and 20.0% discoloration microcapsules in topcoat. The results provided a reference for multifunctional wood coatings.

Challenges and strategies in high-accuracy manufacturing of the world’s largest SiC aspheric mirror

In the process of manufacturing the world’s largest silicon carbide (SiC) aspheric mirror, the primary difficulties are mirror blank preparation, asphere fabrication, and testing, as well as cladding and coating. Specifically, the challenges include the homogeneity of the complicated structure casting, accuracy and efficiency of the fabrication process, print-through effect, fidelity and precision of test procedure, stress and denseness of cladding process, the dynamic range of interferometric measurement, and air turbulence error due to the long optical path. To break through such a barrier of difficulties, we proposed the water-soluble room temperature vanishing mold and gel casting technology, homogeneous microstructure reaction-formed joint technology, nano-accuracy efficient compound fabrication, gravity unloading technology, high-denseness low-defect physical vapor deposition (PVD) Si-cladding technology, test data fusion method, and time-domain averaging method, etc. Based on the proposed technologies and methods, we have accomplished the world’s largest SiC aspheric mirror with a size of ⌀4.03 m. The impressive performance of the SiC aspheric mirror is validated by the characteristics of the fabricated SiC aspheric mirror. The aerial density of the SiC blank is less than 120 kg/m2, surface shape test accuracy is better than 6 nm RMS, thickness inhomogeneity of the cladding layer is less than 5%, and the final surface figure error and roughness are 15.2 nm RMS and 0.8 nm RMS, respectively.

Effect of TiC on the high-temperature oxidation behavior of WMoTaNbV refractory high entropy alloy fabricated by selective laser melting

The refractory high-entropy alloys possess both high melting points and excellent high-temperature properties. As a result, they are expected to become a new generation of high-temperature materials. Along these lines, in this work, selective laser melting (SLM) was used to prepare WMoTaNbV and TiC/WMoTaNbV-based alloys, while the influence of the SLM process parameters on the surface morphology, internal defects distribution and microstructure of the alloy was thoroughly analyzed. On top of that, the long-term high-temperature oxidation behavior of the two alloys at 600°C was studied. The extracted results showed that the process parameters had a serious impact on the surface quality and internal defects of the refractory high-entropy alloys. By optimizing the process parameters, the final surface roughness value of the WMoTaNbV-based alloy was 9.148 μm (Sa). On the contrary, the surface roughness value of the TiC/WMoTaNbV compound was 14.218 μm (Sa). It is also interesting to notice that the incorporation of TiC could significantly reduce the number of cracks within the TiC/WMoTaNbV alloy. Moreover, the WMoTaNbV-based alloy was mainly composed of dendritic structures, while the TiC/WMoTaNbV-based alloy consisted of cellular structures. The main oxidation products of the WMoTaNbV-based alloy were the Ta16W18O94 and Nb14W3O47 ternary oxidation products. After the TiC particles were added, the Ti-containing oxidation products such as TiO2, Ti2Nb10O29. etc. within the TiC/WMoTaNbV-based alloy increased significantly, preventing thus effectively the alloy from being seriously oxidized. The cellular structures, carbides and TiO2 phase are helpful in improving the oxidation resistance of the TiC/WMoTaNbV-based alloy.

Influence of Heat Treatment on Microhardness and Surface Roughness of Electroless Ni-YSZ Composite Coating

The application of heat treatment was introduced in Ni-YSZ composite coating as the incorporation of ceramic YSZ in electroless nickel deposition is new and worth investigating. In this paper, the influence of heat treatment by varying the heating temperature and time on the electroless Ni-YSZ composite coating is investigated. The Ni-YSZ composite is deposited onto a high-speed steel substrate via electroless nickel co-deposition. YSZ powder of mixed sizes of micro- and nano-sized of the ratio of 1:1 is incorporated in the electroless deposits. The electroless Ni-YSZ composites coating was heated up to 400oC for a maximum of 2 hours. The microhardness measurements were carried out using a Vickers microhardness tester (Shimadzu) according to ISO 6507-4. The surface roughness of the coating was measured using Mitutoyo surface roughness tester SJ-301. The surface characterisation was analysed using Cambridge Stereoscan 90 Scanning Electron Microscope (SEM) coupled with Energy Dispersive X-ray Analysis (EDX). The crystallographic structure of materials was analysed by X-ray diffraction (XRD) Bruker D8 Advance instrument. The microhardness and surface roughness of the coating both increase with time. The microhardness is directly proportional to the heating temperature and time and these observations are supported by the XRD analysis. The surface roughness observation is explained by the SEM micrographs.

Micro-nanoarchitectonics of electroless Cu/Ni composite materials based on wood via heat treatment

This research aims to optimize the comprehensive performance of wood-based electromagnetic shielding interference (EMI) materials and master the effect of heat treatment on its coating density, interfacial morphology, conductivity, and hydrophobic and electromagnetic shielding. The results showed that the surface roughness of composite coatings was 11.0 μm when the wood was conducted via electroless two deposition Cu and one Ni and the heat treatment temperature was 150 °C. The composite coating’s surface gradually became more uniform with increasing temperature. The coating’s thickness via 120 °C heat treatment was 97.5 μm. Energy Dispersive Spectroscopy (EDS) spectra verified the existence of Cu and Ni particles. The heat treatment had an obvious influence on conductivity of composite materials and the pore network structure. The contact angle of composite materials reached 119°. The average electromagnetic shielding efficiency via 180 °C heat treatment was up to 91.4 dB in the frequency ranging from 300 to 3.0 GHz, which verified that the composite materials can shield 99.99% of the incident electromagnetic wave energy. The conductivity gradient structure can realize multi-dielectric interface loss and multiple reflection loss.

An Orthogonal Experimental Study on the Preparation of Cr Coatings on Long-Size Zr Alloy Tubes by Arc Ion Plating.

Cr-coated Zr alloys are widely considered the most promising accident-tolerant fuel (ATF) cladding materials for engineering applications in the near term. In this work, Cr coatings were prepared on the surfaces of 1400 mm long N36 cladding tubes using an industrial multiple arc source system. Orthogonal analyses were conducted to demonstrate the significance level of various process parameters influencing the characteristics of coatings (surface roughness, defects, crystal orientation, grain structure, etc.). The results show that the arc current mainly affects the coating deposition rate and the droplet particles on the surface or inside the coatings; however, the crystal preferred orientation and grain structure are more significantly influenced by the gas pressure and negative bias voltage, respectively. Then, the underlying mechanisms are carefully discussed. At last, a set of systemic methods to control the quality and microstructures of Cr coatings are summarized.