Surface Roughness Of Coatings Research Articles

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.

Modelling surface roughness in finish turning as a function of cutting tool geometry using the response surface method, Gaussian process regression and decision tree regression

In this study, the modelling of arithmetical mean roughness after turning of C45 steel was performed. Four parameters of cutting tool geometry were varied, i.e.: corner radius r, approach angle κ, rake angle γ and inclination angle λ. After turning, the arithmetical mean roughness Ra was measured. The obtained values of Ra ranged from 0.13 μm to 4.39 μm. The results of the experiments showed that surface roughness improves with increasing corner radius, increasing approach angle, increasing rake angle, and decreasing inclination angle. Based on the experimental results, models were developed to predict the distribution of the arithmetical mean roughness using the response surface method (RSM), Gaussian process regression with two kernel functions, the sequential exponential function (GPR-SE) and Mattern (GPR-Mat), and decision tree regression (DTR). The maximum percentage errors of the developed models were 3.898 %, 1.192 %, 1.364 %, and 0.960 % for DTR, GPR-SE, GPR-Mat, and RSM, respectively. In the worst case, the maximum absolute errors were 0.106 μm, 0.017 μm, 0.019 μm, and 0.011 μm for DTR, GPR-SE, GPR-Mat, and RSM, respectively. The results and the obtained errors show that the developed models can be successfully used for surface roughness prediction.

Influence of the content of aluminum on the structure of gradient detonation coatings based on NiCr-Al

This paper studies the effects of aluminium content in the composite powder on the structure of detonation gradient coatings based on NiCr-Al. Gradient coatings were obtained by detonation spraying with a gradual stepwise decrease in the barrel filling volume with an acetylene-oxygen gas mixture from 50% to 25%. The elemental and phase composition, microstructure and surface roughness of coatings based on NiCr-Al with different aluminium content of 15%, 20%, and 30% were investigated. By varying the aluminium content in the powder composition, coatings with a gradient structure were obtained. The study results showed that the phase composition of the gradient coating strongly depends on the mass fraction of Al. In the case of an aluminium content of 30% in the composition of the composite powder, the formation of aluminium oxide was detected. It is established that under the same detonation deposition modes, the formation of the gradient structure of coatings will strongly depend on the aluminium content in the NiCr-Al composition. The study results showed that the optimal composition of the powder is NiCr – 80% and Al – 20% to obtain NiCr-Al coatings with a gradient structure.

EFFECT OF ARC CURRENT ON MECHANICAL PROPERTIES OF AlCrN COATINGS DEPOSITED USING CATHODIC ARC EVAPORATION

The AlCrN coatings were formed using cathodic arc evaporation at constant nitrogen pressure and arc current ranged from 50 to 120 A. Scanning electron microscopy, energy dispersive analysis, X-ray diffractometry, nanoindentation, adhesion tests and friction tests were used to investigate the effect of arc current on surface morphology, composition, structure, and mechanical and tribological properties of coatings. It was found that all coatings present cubic AlCrN with Al/(Al+Cr) ratio independent on arc current. Increase in the arc current results in increase in lattice parameter, crystallite size as well as deposition rate and coating surface roughness. A decrease in hardness with a simultaneous increase in Young's modulus is also observed. The adhesion of the coatings shows a non-linear character with the maximum (108 N) for the coating formed at an arc current of 80 A, which may explain the best wear resistance – the lowest wear rate 1.4·10-7 mm3/Nm.

Surface properties and biocompatibility studies on bone plate by magnetorheological finishing

ABSTRACT Bone plates are essential for providing mechanical support during the healing of bone fractures by adapting to the biochemical environment. The surface quality of bone plates plays a vital role in their sustainability under adverse conditions. Magnetorheological Finishing (MRF) is an advanced surface finishing process that provides high surface finishing without disturbing the polished surface topography. However, while mapping to the workspace has a hole or pocket feature, the Magnetorheological (MR) fluid is not stable and gets trapped inside. Hence, a Feature-based hybrid MRF planning system is developed to overcome the challenge during MRF. The final average surface roughness (Ra) value of 21.56 nm from its initial roughness value of 324.12 nm is achieved on the polished surface bone plate made of Ti–6Al–4V. The enhancement in the surface characteristics of the MRF polished surface leads to the biomaterial's enhanced wear and corrosion resistance.

Effect of rotary ultrasonic machining parameters on surface integrity of advanced ceramics

The commercial use of advanced ceramics has been hampered by the lack of an efficient, low-cost machining process. Two of the most important requirements for making machining of ceramics economically viable are: i) obtaining high enough material removal rates and ii) developing a machining process that does not cause surface and subsurface damage to the ceramic component. Therefore, it is important to study, in-depth, machining processes that have the potential to machine advanced ceramics efficiently and reliably. In this study, two-level full factorial experiments were designed and run to determine the effect of rotary ultrasonic machining process parameters (grit size, vibration amplitude, and feed rate) on the process outputs (cutting force, surface roughness, and surface compressive residual stresses). The materials under investigation were sintered silicon nitride and sintered reaction-bonded silicon nitride. The experiments reveal the main effects as well as the interaction effects of the process parameters on the process outputs such as cutting force, surface roughness, and surface compressive residual stresses. Using a larger grit size has been found to decreases the tool axial force. Samples that had a rougher surface finish also showed the highest surface residual compressive stresses. Surface compressive residual stresses were present in all samples after rotary ultrasonic machining irrespective of the conditions used. The presence of surface residual compressive stresses was found to be independent of the direction of machining.

Effect of particle size on surface roughness and morphology of heat-treated electroless Ni-YSZ coating

The paper discusses the surface characterisation of electroless nickel-yttria-stabilised zirconia (Ni-YSZ) coating with varying YSZ particle sizes and undergoes heat treatment at a temperature between 300-400°C for 1-2 hours for wear resistance purposes. This finding will be helpful to the application of Ni-YSZ as an alternative coating for cutting tools. The surface characterisation was analysed using JOEL Scanning Electron Microscope (SEM) coupled with Energy Dispersive X-ray (EDX) JSM 7800F. The crystallographic structure of materials was analysed by X-ray diffraction (XRD) Bruker D8 Advance instrument. The Ni-YSZ coating was deposited using electroless nickel co-deposition of 8YSZ ceramic particles with a nano, mixed and microparticle sizes onto a high-speed steel (HSS) substrate. The coatings were heat treated at temperature 300-400°C and time 1-2 hours. The surface roughness was measured using Mitutoyo surface roughness tester SJ-301. The electroless Ni-YSZ coating deposited has an average thickness of 30 µm. It is found that the coating morphology electroless coating without YSZ particle incorporation (EN) and Ni-YSZ nano (N) is smoother compared to the Ni-YSZ mixed (NM) and Ni-YSZ micro (M). The EDS composition analysis shows the YSZ content in the electroless Ni-YSZ coating for N samples is the lowest, whereas NM samples are the highest. This resulted in the surface roughness behaviour where the mixed-size YSZ particle gives the highest roughness at all temperatures. The XRD analysis shows that heating temperatures above 300°C caused the precipitation of Ni3P crystalline. Previous studies in the surface characterisation of electroless nickel composite are scarce; thus, the study has limitations in finding supporting data. The surface characterisation especially related to the surface roughness of the electroless nickel, either the Ni-P or composites or alloys are rarely reported. Thus, this study enlightened the effect of particle size on surface roughness and morphology of heat-treated coatings.

Corrosion of 316L Stainless Steel used for Building Applications in Marine–Urban Atmospheres: A Case Study from Genoa, Italy

This study concerns the corrosion behavior of a 316L stainless steel railing installed in an aggressive marine–urban atmosphere, located about 400 m as the crow flies from the sea, in Genoa, a coastal city in northwestern Italy. Despite the well-known relevance of surface finishes in determining the degree of resistance to atmospheric corrosion, the initial surface finish of the material used could not be ascertained. Only 3 months after it was erected, the railing showed, upon visual inspection, reddish-brown halos and spotted deposits distributed diffusely all over the structure. To investigate the likely causes of these sudden and unexpected corrosion phenomena, the morphology of the corrosion and the surface chemical compounds were examined using microscopic (optical and scanning electron, with an electron probe microanalyzer equipped with an energy-dispersive spectrometer) and profilometry (no-contact three-dimensional optical profiling) techniques. The morphology of the steel surface finish on the specific material used for the structure was found to be unsuitable for its designated use in such an aggressive atmosphere. Chloride occurring along the constituent grain boundaries of the rough surface finish triggered intergranular corrosion, leading to grain fall out and subsequent significant localized corrosion.

Multi-pass EDM process planning for the surface treatment of powder-bed-fusion AM CORRAX mold steel

Although it is time-consuming to perform multi-pass electrical discharge machining (EDM) processes, EDM is exceedingly feasible for processing the partially unmelt profile of Powder-Bed-Fusion additive manufacture mold steel. This study is based on the principle of removing three times the thickness of the recast layer and reducing the EDM processes depth. And then, the surface quality and the processing time with EDM passes are decreased by adjusting the EDM passes suggested by the machine builder. Secondly, reduction of four more passes and the predetermined depth of processing so that the total processing time can be reduced further. Finally, the efficiency is increased by more than 77% compared to machine builder’s processes, and the final surface roughness reaches the specification of 0.17 μm Ra. The HAZ and recast layer thickness are also reduced drastically and distributed uniformly. Therefore, a new version of the EDM process planning suitable for AM CORRAX mold surface treatment is proposed, and its processing efficiency and surface integrity are investigated.

CFD of roughness effects on laminar heat transfer applied to additive manufactured minichannels

AbstractAdditive manufacturing has received significant interest in the fabrication of functional channels for heat transfer; however, the inherent rough surface finish of the additively manufactured channels can influence thermal performance. This study investigates the impact of roughness on the thermo-fluid characteristics of laminar forced convection in rough minichannels. A numerical model was developed to create 3D Gaussian roughness with specified root-mean-square height. The finite volume method was used to solve the conjugate heat transfer of developed laminar flow in square minichannels. For Reynolds numbers ranging from 200 to 1600, the simulation results indicated enhanced heat transfer and increased flow resistance as Reynolds number increases, compared to a smooth minichannel, where effects on heat transfer and flow friction were negligible. For channels with relative roughness (root-mean-square height to channel hydraulic diameter) of 0.0068, 0.0113, and 0.0167, increasing the Reynolds number led to increased friction factor by 1.56, 1.71, and 2.91%, while the Nusselt number was enhanced up to 0.03%, 32.74%, and 46.05%, respectively. Heat transfer reduced in roughness valleys due to the presence of local low-velocity fluid in these regions; however, recirculation regions can occur in deep valleys of high roughness, increasing heat transfer and flow friction. Heat transfer was enhanced over roughness peaks due to flow impingement on the windward face of roughness as well as intensified energy transfer to the channel wall from roughness. Moreover, surfaces with higher roughness have a greater number of high peaks providing a thermal-flow path of a larger area and a thermal conductivity greater than that of the fluid.

Prediction of Surface Roughness of SLM Built Parts after Finishing Processes Using an Artificial Neural Network

A known problem of additive manufactured parts is their poor surface quality, which influences product performance. There are different surface treatments to improve surface quality: blasting is commonly employed to improve mechanical properties and reduce surface roughness, and electropolishing to clean shot peened surfaces and improve the surface roughness. However, the final surface roughness is conditioned by multiple parameters related to these techniques. This paper presents a prediction model of surface roughness (Ra) using an Artificial Neural Network considering two parameters of the SLM manufacturing process and seven blasting and electropolishing processes. This model is proven to be in agreement with 429 experimental results. Moreover, this model is then used to find the optimal conditions to be applied during the blasting and the electropolishing in order to improve the surface roughness by roughly 60%.

Tribological Properties of Chromia and Chromia Composite Coatings Deposited by Plasma Spraying

Cr2O3 and Cr2O3–SiO2-TiO2 coatings are deposited on P265GH steel using atmospheric plasma spraying. The influence of silicon oxide—titanium oxide addition on the surface morphology of the coatings, phase composition and tribological properties under non-lubricated sliding conditions are investigated. The addition of SiO2-TiO2 led to the formation of a more uniform surface morphology and reduce the surface roughness of the Cr2O3 coatings. The X-ray diffraction (XRD) studies indicated that both coatings are composed of an eskoloite Cr2O3 phase. The friction coefficients of the Cr2O3 coating are 0.504 and 0.431 when 1 N and 3 N loads were used, respectively. Meanwhile, the Cr2O3–SiO2-TiO2 coating demonstrated slightly lower values of friction coefficients under similar loads. The specific wear rate of the as-sprayed coating is reduced with the addition of SiO2-TiO2. It was found that the wear rates of the Cr2O3 and Cr2O3–SiO2-TiO2 coatings are up to 20 times lower compared to the steel substrate. This article is an expanded version of the “19th international conference on plasma physics and applications” conference abstract.

The Impact of Selected Laser-Marking Parameters and Surface Conditions on White Polypropylene Moldings

Laser marking of polymer materials is a technology that is increasingly used in industry. Polypropylene (PP) shows a low ability to absorb electromagnetic radiation in the near-infrared range (λ = 1064 nm). The paper presents the influence of the surface condition of white-colored polypropylene moldings on the efficiency of their marking with a laser beam. In addition, the operation of the commercial laser marking additive (LMA) Lifolas M 117009 UN, intended to support the process of laser marking of polyolefin surfaces, was verified. The study is an attempt to combine laser operating parameters, material, and geometric properties of PP moldings to obtain the expected quality of graphic symbols. The test samples were made by injection molding method with the use of a specially designed modular injection mold. The molding cavities were prepared with various methods of metal processing, thanks to which obtained moldings differed in surface condition. The marking effects were assessed based on colorimetric tests and digital image analysis. The 0.5 wt% LMA content resulted in obtaining a graphic sign with high contrast in comparison to the background. The gradual increase in the modifier content resulted in a further increase in contrast. These values depended on the degree of surface finish of the samples, and therefore on the roughness parameters. Samples with a rough surface finish showed higher contrast compared to surfaces with a high surface finish. It was also found that for the analyzed moldings, the laser-marking process should be performed with the use of a low head velocity (450–750 mm/s) and a high concentration of the laser beam (0.03–0.05 mm).

Surface Roughness and Design for Additive Manufacturing: A Design Artefact Investigation

AbstractLaser Powder Bed Fusion (LPBF) brings the possibility to manufacture innovative near-net-shape part designs. But unfortunately, some designed surfaces suffer from rough surface finish due to characteristics of the LPBF process. This paper explores trends in managing surface roughness and through a space industry case study, a proposed process that uses Additive Manufacturing Design Artefacts (AMDAs) is used to investigate the relationship between design, surface roughness and fatigue. The process enables the identification of design uncertainties, however, iterations of AMDA's can be required.

Improvement of Structures and Properties of Al2O3 Coating Prepared by Cathode Plasma Electrolytic Deposition by Incorporating SiC Nanoparticles

A serious issue in the preparation of Al2O3 coatings by cathode plasma electrolytic deposition (CPED) is that the coatings have a porous structure, which is detrimental to their protective performance. Therefore, to address this problem, SiC nanoparticles are incorporated into the Al2O3 coating in this study. A series of Al2O3–SiC composite coatings are efficaciously prepared on the surface of 316L stainless steel by CPED. The microstructures, compositions and phase components of the composite coatings are characterized; the electrochemical corrosion resistance and tribological behavior are evaluated; and the mechanism of SiC nanoparticles in the coating formation process is discussed in detail. The results indicate that the Al2O3 coating prepared by CPED consists of α-Al2O3 and γ-Al2O3, and the former is the main crystalline phase. With the incorporation of SiC nanoparticles in the coating, the content of α-Al2O3 gradually decreases, almost disappearing, accompanied by an increase in γ-Al2O3 as the main crystalline phase. The incorporation of SiC nanoparticles significantly reduces the surface irregularity and roughness of Al2O3 coatings and remarkably improves the corrosion resistance and wear resistance of the Al2O3 coatings. The improvement in corrosion resistance and anti-wear properties can be explained by the fact that the SiC nanoparticles effectively weaken electrical breakdown and increase the compactness of the coatings.

Enhancing cytocompatibility, antibacterial activity and corrosion resistance of PEO coatings on titanium using incorporated ZrO2 nanoparticles

This study aims to present the influence of adding three different concentrations (1, 3, and 5 g/L) of ZrO2 nanoparticles (NPs) into the electrolyte of the plasma electrolytic oxidation (PEO) process on prepared composite coatings characteristics on Ti substrate. The structural and compositional analysis confirmed that ZrO2 NPs can incorporate on the surface and inside the pores of coatings, while it may emerge as the ZrTiO4 phase in the coatings’ composition. The higher concentration of NPs increased porosity percentage and thickness of coatings. The wettability and surface roughness of coatings were realized to relate to the NPs concentration directly. The electrochemical features of coatings were investigated after exposure to simulated body fluid (SBF) for 7 days. The highest corrosion resistance (1.69 MΩ.cm2) was achieved by adding 5 g/L ZrO2 NPs. At the same time, we found out that the most desirable MG63 cell biocompatibility in terms of cell adhesion and flattening was attributed to the smaller ZrO2 NPs addition. The antibacterial activity of coatings against S. aureus bacteria was found to increase from 63.30 ± 2.47 up to 94.37 ± 2.25 % within 24 h. This work endows an exciting path for developing advanced PEO coatings on Ti-based implants.

Early stage growth of amorphous thin film: Average kinetics, nanoscale dynamics, and pressure dependence

We used the coherent grazing incidence small angle x-ray scattering technique to study the average kinetics and nanoscale dynamics during early-stage a-${\mathrm{WSi}}_{2}$ sputter deposition. The kinetic and dynamic properties are examined as a function of pressure, which is known to be a critical factor in determining final surface roughness. Surface growth kinetics and dynamics are characterized by time parameters extracted from the height-height structure factor and correlation functions. The roughness at a given length scale reaches a maximum before relaxing down to a steady state. The lateral length scale dependence and pressure dependence are then compared among the measured kinetics and dynamics time parameters. Surfaces grown at lower pressures are smoother, leading to longer correlation times. The time parameters to reach a dynamic steady state and a kinetic steady state show contrasting pressure dependence. A dynamic steady state is reached earlier than the kinetic steady state at high pressure. A more random deposition direction and lower kinetic energy at higher pressures can explain these phenomena, along with the hypothesis that larger nanoclusters form in vapor before arriving at the surface. A continuum model is applied to simulate the overall behavior with mixed success.

Electrochemical Polishing of Tungsten: An Investigation of Critical Spatial Frequency and Ultimate Roughness

Electrochemical polishing (ECP) offers incomparable advantages and great potential in metal polishing by surface errors correction. This paper systematically investigates the ultimate roughness and surface errors correction ability of ECP over different spatial frequency ranges. This paper further explores the law of ECP influencing errors at different frequency ranges, proposes and clarifies the concept of critical spatial frequency, and studies the law of polishing parameters affecting critical spatial frequency by using spatial frequency spectrum analysis. The surface roughness evolution and ultimate roughness of ECP were investigated using the surface error filtering method based on the critical spatial frequency. The ultimate roughness of ECP was determined by two different strategies, (i) stepwise polishing and (ii) one-step polishing. In addition, the stepwise polishing was also investigated for any possible inconsistency with one-step polishing on the final surface roughness. As ECP progressed, the optimization speed of surface roughness gradually decreased, and the surface roughness eventually reached a stable limiting value. Further analysis revealed that crystal corrosion is mainly responsible for inhibiting surface roughness optimization.