Ni-based Coatings Research Articles

Numerical Optimization and Performance Study of Ni-Based Coatings on Gray Cast Iron Surface by High-Speed Laser Cladding Based on Orthogonal Test

Numerical Optimization and Performance Study of Ni-Based Coatings on Gray Cast Iron Surface by High-Speed Laser Cladding Based on Orthogonal Test

Corrosion of Ni-based alloy coatings prepared by laser cladding in high-temperature chloride environment

Due to the complex incineration environment of waste incineration power generation boilers generates large amounts of acidic gases (such as Cl2 and HCl) and alkali metal chlorides (such as NaCl and KCl), leading to boiler corrosion failure. Herein, a new type of NiCrAlTi alloy coatings was deposited on 304 stainless steel surfaces by laser cladding technology. High-temperature corrosion experiments were then carried out at 650 °C for 64 h and the results were compared with those of traditional Inconel625 alloy coating. The high-temperature chloride corrosion mechanism and the corrosion resistance of alloy coatings were examined. The results revealed the decomposition of chlorides, such as HCl, NaCl, and KCl into Cl2 at high temperatures as the source of corrosion of high-temperature chlorides. The released C12 reacted with the metals present in the coating to form nonprotective metal chlorides. The low melting point and high vapor pressure of metal chlorides allowed their transition into a gaseous state to diffuse outward and oxidize into Cl2. In turn, the released Cl2 reacted with the metal to induce corrosion. During the corrosion process of NiCrAlTi alloy coating, a Cr depletion zone was induced, and a continuous Al2O3/TiO2/Cr2O3 three-layer protective film was formed on the coating surface, conducive to better alleviating the corrosion caused by the reaction between Cl2 passing through the film and the metal substrate. Under the conditions of this experiment, the corrosion resistance of NiCrAlTi alloy coating is 1.8 times that of the common material 304 stainless steel, and about 1.2 times that of Incon625 alloy coating. With the extension of the experiment, its corrosion resistance will be better. Overall, rich experimental data and theoretical guidance were provided for further research and development on high-temperature chloride corrosion-resistant alloys or coating materials for high-efficiency cost-effectiveness boilers.

Evaluation of Tribological Characteristics of Atmospheric Plasma Spray Deposited Ni-Based Coatings

Evaluation of Tribological Characteristics of Atmospheric Plasma Spray Deposited Ni-Based Coatings

Electrochemical Deposition and Properties of Ni Coatings with Nitrogen-Modified Graphene Oxide

In this study, a method for producing nitrogen-modified graphene oxide (NMGO) using hydrothermal synthesis in the presence of triethanolamine is presented. The composition and structure of NMGO are characterized using X-ray phase analysis (XPA), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and Raman spectroscopy. Ni-based metal matrix coatings (MMCs) modified with NMGO were obtained from a sulfate-chloride electrolyte in the galvanostatic mode. The process of electrochemical deposition of these coatings was studied using chronovoltammetry. The microstructure of Ni–NMGO MMCs was studied using the XPA and SEM methods. It has been established that the addition of NMGO particles into the Ni matrix results in an increase in the microhardness of the resulting coatings by an average of 1.30 times. This effect is a consequence of the refinement of crystallites and high mechanical properties of NMGO phase. The corrosion-electrochemical behavior of studied electrochemical deposits in 0.5 M sulfuric acid was analyzed. It has been shown that the corrosion rate of Ni–NMGO MMCs in a 3.5% sodium chloride environment decreases by approximately 1.50–1.70 times as compared to unmodified Ni coatings. This is due to NMGO particles that act as a barrier preventing the propagation of the corrosion and form corrosive galvanic microelements with Ni, promoting anodic polarization.

Electrodeposition of nanocrystalline Ni and NiCr alloy coatings: Effects of Cr content on microhardness and wear resistance improvement

The safety and reliability of high-speed trains depend on the brake disc. In order to improve the lifetime of brake disc and reduce the waste of resources, a coating with higher microhardness and well wear resistance is urgently needed. The effect of chromium content on the microstructure, microhardness and wear resistance of NiCr coating has been studied. Nano-crystalline Ni and NiCr coatings with superior mechanical properties were successfully prepared on the 30CrNiMo steel substrate by pulse current electrodeposition method. The inclusion of formic acid and sodium citrate was found to significantly expedite the co-deposition of Ni and Cr. The NiCr coatings with various Cr contents were prepared at current densities ranging from 200 to 300 mA/cm2. These coatings significantly enhance microhardness and wear resistance of the substrate. The microhardness of the NiCr coating increased to 603 HV, outperforming pure Ni coating by 119 HV. Additionally, the wear rate of the NiCr coating decreased by 50% at a load of 10 N in comparison to the Ni coating. The high microhardness is attributed to grain refinement and solution strengthening. This study successfully addresses the challenges associated with electrodepositing Ni-based coatings on 30CrNiMo steel substrate and lays a theoretical foundation for the utilization of Ni-based coatings to enhance the tribological properties of materials used in high-speed train brake disc.

INFLUENCE OF SPRAY DISTANCE ON THE POROSITY OF Ni-BASED AMORPHOUS COATINGS: NUMERICAL SIMULATION AND EXPERIMENT

The influence of injection distance on the porosity of Ni-based amorphous coatings (AMCs) prepared with a high-velocity air fuel (HVAF) process is discussed based on a numerical analysis and experimental methods. A computational fluid dynamics model was established to demonstrate the gas flow field and behavior of particles in flight at different spraying distances during HVAF spraying. When analyzing the changes in the particle velocity and temperature, the spraying distance is less than 30 µm. The velocity and temperature changes of small particles have a significant impact, and the optimal spray distance (350 mm) for obtaining a low porosity coating is predicted. The calculation was validated experimentally by producing a Ni-based AMC with a low porosity (1.87 %) that was manufactured using the predicted HVAF optimal spraying distance.

Erosion Prediction Gaussian Process Regression Algorithm for Alumina and Chromia Reinforced Nickel-Based High-Velocity Oxy-Fuel Coatings

Background:: Machine learning (ML) methodologies have demonstrated efficacy in the determination of erosion rates and material removal. In this context, a novel Erosion Prediction Gaussian Process Regression Algorithm (EPGPRA) was developed to predict the volumetric erosion in thermal spray coatings. Aim:: In this patent, a novel EPGPRA based model was developed to predict the volumetric loss of 30Al2O3 and 20Cr2O3 reinforced Ni-based coatings deposited using a high-velocity oxy-fuel (HVOF) process. Objective:: The objective of this patent is to develop a GPR model for the prediction of Ni-30Al2O3 and Ni-20Cr2O3 coatings. Methods:: Spraying powders were applied to the SS316L steel substrate in order to develop coatings. An erosion tester was used in order to investigate the wear resistance of HVOF-coated steel. The gathered experimental dataset is put to use in the construction of a powerful GPR model. The outcomes from GPR model were then measured against the values obtained from the experiments. To demonstrate the accuracy of the GPR model, the produced model is evaluated against various cutting-edge machine learning methods. Results:: This innovation was successful in terms of developing a new GPR model for wear prediction. The discrepancy between the actual and expected values is the smallest for Matern 5/2 (M5/2) GPR in the validation set. It was also lesser as compared to Ensemble Boosted Trees, Support Vector Machine, Linear regression, and Fine Tree. In terms of MSE, MAE, RMSE, and R2 the accuracy performance of the M5/2 GPR model was determined to be 9.8565×10-5, 0.0048884, 0.009928, and 0.93 correspondingly. Ni-Chromia coating performed better than the Ni-Alumina. Conclusion:: As per this patent, a novel EPGPRA-based model was developed, which is the better machine learning technique for wear prediction of Ni-based HVOF coatings.

Review of laser cladding coating on wear and fatigue of railway wheels/rails

With the rapid development of high-speed railway, wheel/rail premature wear and fatigue cracks occur frequently. Laser cladding high-quality coatings with high wear resistance and fatigue resistance on the damaged surface of wheel/rail can prolong its service life. In this review, the latest research progress of laser cladding Fe-based, Co-based and Ni-based coatings on the wear and fatigue of railway wheels/rails at home and abroad is reviewed. It is concluded that the wear resistance and fatigue resistance of Co-based alloy coatings are better than those of other alloy coatings. Adding strengthening elements to alloy powders can improve the welding process and improve the comprehensive properties of the coatings. Additionally, the laser cladding of railway wheel/rail is further envisaged as well.

Effect of rare earth La2O3 particles on structure and properties of laser cladding WC-Ni60 composite coatings

In the production of polysilicon, valve sealing surfaces are vulnerable to issues such as erosion wear from silicon powder, corrosion from chloride ions, and leakage leading to functional failure. This paper proposes a process route for laser cladding rare earth La2O3 doped Ni-based WC coatings on the surface of AISI 304 steel, and carries out a study on the macroscopic morphology, microstructure, physical phase evolution pattern, wear resistance and corrosion resistance of WC-Ni60 composite coatings from different particle sizes of rare earth La2O3. The results show that the addition of rare earth La2O3 optimized the macroscopic morphology and microstructure of WC-Ni60 coatings, and improved the wear and corrosion resistance of the coatings. Among them, micron-La2O3 showed the most significant improvement in the performance of WC-Ni60 coatings, with wear and self-corrosion current density reduced by 71.43 % and 59.63 %, respectively, compared with the substrate.

Composition Design of Ni-Nano-Cu-BTC@Ag Coatings with Low Friction and Their Intelligent Electrical Control Behavior.

At present, Ni-based coatings are rarely used in the field of voltage control friction because of their poor antifriction, wear resistance, and conductive properties. Therefore, in this paper, Cu-BTC@Ag nanocrystals were used to enhance the nickel coatings, and the effect of voltage on their tribological properties was also investigated. It was found that the grains of coating were refined via the addition of Cu-BTC@Ag nanocrystals, leading to an improvement in the hardness and corrosion resistance of this composite coating. The tribological performance of nickel composite coating could be controlled under different electrical fields. With the comparison of the pure Ni-based coating, the average friction coefficient and wear volume of its composite coating with 5 wt % Cu-BTC@Ag were reduced by 7.0 and 91.8%, respectively, which showed excellent wear resistance without an applied voltage. Under the condition of 20 V, the 5 wt % Cu-BTC@Ag/Ni-based composite coating owned outstanding antifriction performance. Therefore, Cu-BTC@Ag played an intelligent role in regulating the friction of Ni-based coatings under an external voltage. It is due to the accumulation of Cu-BTC@Ag nanocrystals on the surface of the coating under the action of voltage, which played the role of supporting load and effectively reducing wear.

Effect of laser remelting on internal defects and properties of Ni-based coatings reinforced by multi-channel WC in situ

In order to investigate the effect of laser remelting on the properties of hot work die steel, WC reinforced Ni base remelting layer was prepared on H13 steel surface. Optical metallography microscope, X-ray diffractometer and scanning electron microscope were used to analyze the macroscopic defects, phase evolution and microstructure of the coating before and after laser remelting. Microhardness tester and friction and wear tester were used to test the microhardness and wear resistance of the remelted layer, and compared with the coating without remelting. The results show that the inner porosity of the coating decreases with the increase of laser power. With the dissolution of WC/W2C ceramic particles and the uniform distribution of W element, the distribution of reinforcement particles in the coating becomes more and more uniform. When the laser power reaches 1500 W, the WC/W2C ceramic particles inside the coating basically disappear, the porosity is reduced to the lowest, the coating uniformity is the best, and the microhardness and wear resistance are the highest.

Tribological properties of Ni-based composite coatings with addition of Ag@Ni core−shell particles over multiple thermal cycles

In order to inhibit the diffusion of Ag, Ag@Ni core−shell structure particles were prepared by the electroless plating, and then the NiCrAlY−Mo−Ag@Ni coatings were prepared by atmospheric plasma spraying. The effects of core−shell structure design on the mechanical and tribological properties of the coatings over multiple thermal cycles were researched in detail. The results show that the core−shell structure design of Ag could enhance the interfacial bonding strength between Ag and NiCrAlY by the Ni-coated layer, and then improve the hardness of the coating obviously. The Ni-coated layer inhibits the diffusion and dissipation of Ag effectively in the friction process at high temperatures. The friction coefficient and wear rate of the NiCrAlY−Mo−Ag@Ni coating tested at 800 °C are only about 0.25 and 1×10−5 mm3/(N·m), respectively, which are obviously lower than those of the NiCrAlY−Mo−Ag coating. Meanwhile, the core−shell structure design of Ag endows the coating with excellent self-lubricating and wear resistance over multiple thermal cycles.

Microstructure and properties of Ni-based VC and TiVC2 composite coatings fabricated in situ by laser direct deposition

Ni-based VC and TiVC2 composite coatings were prepared on the surface of worn brake discs by laser direct deposition, and the influence mechanism of trace TiC addition on the microstructure and performance of the coating was investigated. The microstructure of the coatings was analyzed by XRD, SEM, EDS, and TEM, which revealed the evolution mechanism of the microstructure during the laser deposition process. The friction wear performance was tested on friction wear equipment. The results showed that VC0.88 was formed by the in-situ reaction of C and V under the action of the laser, which presents dendritic morphology. After the addition of TiC particles, TiVC2 was further synthesized along the TiC particles in addition to dispersed VC0.88 in the coating. It can be seen that the addition of trace TiC particles inhibited the formation of VC0.88 dendrites and enhanced the plastic toughness of the coating. HRTEM calibration proved the existence of TiVC2 and Ni, and there was no obvious orientation relationship between the interface. The friction coefficients of Ni-based VC and Ni-based TiVC2 coatings with Al2O3 balls were 0.59 and 0.51 at room temperature, respectively. After 1.5 h of high-temperature wear at 300 °C and 600 °C, the distribution of wear marks shows a groove and high-temperature fatigue appearance. The TiC-doped coating has better wear properties than the base material and the original coating is expected to meet the requirements for brake discs.

Comparative Study of Corrosion Performance of LVOF-Sprayed Ni-Based Composite Coatings Produced Using Standard and Reducing Flame Spray Stoichiometry.

Coating efficiency and quality can be significantly improved by carefully optimizing the coating parameters. Particularly in the flame spray method, the oxygen/fuel ratio, which is classified as oxidizing flame stoichiometry (excess oxygen) and reduces flame stoichiometry (excess acetylene), and spray distance are the most critical factors, as they correlate significantly with coating porosity and corrosion performance. Hence, understanding the effects of these parameters is essential to further minimize the porosity, improving the corrosion performance of thermally sprayed coatings. In this work, a NiWCrBSi alloy coating was deposited via the oxyacetylene flame spray/Flexicord-wire (FS/FC) method. The effect of the flame oxygen/fuel ratio and spray distance on the microstructure properties and corrosion behavior of the coatings was investigated. Afterwards, the microstructure, phases' compositions, spray distance, and corrosion performance were studied. The equivalent circuit model was proposed, and the corrosion mechanism was discussed. The obtained results highlight that the oxygen-to-fuel ratio is a promising solution for the further application of flame spray/Flexicord-wire (FS/FC) cermet coatings in hostile environments. Depending on the flame's oxygen/fuel ratio, careful selection of the flame stoichiometry provides low porosity and high corrosion performance.

The Effect of Laser-Cladded Co6, T400, and Ni-Based 30WC Coatings on the Wear Resistance of H13 Steel

To enhance the wear resistance of H13 steel (4Cr5MoSiV1), Co6, T400, and Ni-based 30WC coatings were applied to the surface of H13 steel using laser cladding technology. The microstructures and phase compositions of the three coating types were analyzed using SEM and XRD methods. The high-temperature friction and wear performance of the three coated samples and H13 steel were measured through high-temperature friction wear tests, and the friction wear types of the four samples were analyzed. A comparative analysis of experimental data led to the following conclusions: (1) Among the four samples, the Ni-based 30WC-coated sample exhibited the best self-lubricating properties. (2) The average wear area of H13 steel was 0.059 mm2, and the wear volume was 0.29 mm3; the average wear area of Co6-coated samples was 0.050 mm2, and the wear volume was 0.25 mm3; the average wear area of T400-coated samples was 0.002 mm2, and the wear volume was 0.01 mm3; and the average wear area of the Ni-based 30WC-coated sample was 0.035 mm2, and the wear volume was 0.17 mm3. In terms of wear resistance, the ranking from highest to lowest was: T400-coated sample > Ni-based 30WC-coated sample > Co6-coated sample > H13 steel. (3) Based on the classification of friction wear types, H13 steel primarily exhibited adhesive wear and oxidized wear; the Co6- and T400-coated samples primarily showed adhesive wear, abrasive wear and oxidized wear; and the Ni-based 30WC-coated sample mainly exhibited abrasive wear and oxidized wear.

The influence of laser remelting on microstructural changes and hardness level of flame-sprayed NiCrBSi coatings with tungsten carbide addition

The presented article describes the influence of the laser remelting process on microstructural changes, heat-affected zone size, dilution effect and hardness level of hard-facing Ni-based coatings based on NiCrBSi system with the addition of W2C\\WC carbide in the context of thermal diffusivity and specific heat value. This relationship is practically not described in the literature. Three commercial systems, Metco 15E, Metco 36C and customized Metco 15E + DURMAT® FTC, were deposited by flame-spraying on carbon steel with the following laser remelting treatment with different energetical variants. The total deposited in coatings energy value was used as a comparison criterion. The reflectance effect was also considered as a factor influencing the total energy transferred to the coatings. The dilution effect, heat-affected zone size, and hardness level in the context of microstructural changes caused by the laser remelting process in the context of thermal diffusivity were analyzed. It was revealed that the reflectance factor can be omitted as a negligible form point of view of total deposited energy in the coating. The thermal diffusivity of coating materials is similar, but the difference in HAZ and dilution effect is very significant. It can suggest that the thermal diffusivity is an important factor affecting microstructural changing in laser remelting process of flame sprayed NiCrBSi systems, especially when is considered together with specific heat related to presences of different fraction of tungsten carbide.

Effect of a Substrate’s Preheating Temperature on the Microstructure and Properties of Ni-Based Alloy Coatings

Laser cladding is a new technology to fabricate a coating on the surface of a metal substrate. The properties on copper substrates are usually not very good due to the high thermal conductivity and reflectivity. The appropriate preheating temperature is helpful to fabricate coatings with good quality and properties, especially for copper substrates. In order to investigate the effect of different preheating temperatures, four coatings with different preheating temperatures (100, 200, 300 and 400 °C) were fabricated via a laser on a copper substrate. The microstructures and properties of four coatings were investigated using SEM, XRD, EDS, a Vickers microhardness meter, a wear tester and an electrochemical workstation. The results show that the elements from Ni-based alloy powder were uniformly distributed among the binding region, which obtained a good metallurgical bonding. The microstructure was mainly composited of cellular, dendrite and plane crystals, and the main reinforced phases were γ (Fe, Ni), Cr0.09Fe0.7Ni0.21, WC and Ni3B. The values of average microhardness of the four coatings were 614.3, 941.6, 668.1 and 663.1 HV0.5, respectively. The wear rates of the four coatings were 9.7, 4.9, 12.5 and 13.3 × 10−5 mm3·N−1·m−1, respectively, which were less than that of the copper substrate (4.3 × 10−3 mm3·N−1·m−1). The decrease in wear rate was due to the existence of the reinforced phases, such as WC, Ni3B, M7C3 (M=Fe, Cr) and Cr0.09Fe0.7Ni0.21. The fine crystals in the coating preheated at 200 °C also improved the wear resistance. Additionally, the minimum values of corrosion current density were 3.26 × 10−5, 2.34 × 10−7, 4.02 × 10−6 and 4.21 × 10−6 mA·mm−2, respectively. It can be seen that the coating preheated at 200 °C had higher microhardness, lower wear rates and better corrosion resistance due to the existence of reinforced phases and fine and uniform crystals.

Elevated temperature tribological assessment of Ni-based cermet self-lubricating coatings deposited by cold spray

Solid lubricant coatings provide reduced friction and wear resistance and hence finding widespread application in harsh environmental conditions, such as gas turbine, aircraft, and internal combustion engines. It is apparent that single lubricant fails to offer effective lubrication over wide temperature range. Hence, two or more solid lubricants are mutually incorporated to achieve the appropriate lubrication by their synergy under harsh service conditions. The current investigation is being carried out to evaluate the synergistic impact of different solid lubricants viz. silver (Ag), molybdenum disulfide (MoS2), hexagonal boron nitride (h-BN) and chromium oxide (Cr2O3) on the frictional properties of coatings from room temperature (RT) to 800 °C. Cold spraying process has gathered extensive acceptance for the development of metallic and metallic-ceramic coatings. The current study elucidated the tribological characteristics of cold sprayed nickel-based high temperature lubrication coatings, namely, Ni-Al-MoS2-Ag (NB0), Ni-Al-MoS2-Ag-5 wt% h-BN (NB5), Ni-Al-MoS2-Ag-7.5 wt% h-BN (NB7.5), Ni-Al-MoS2-Ag-10 wt% h-BN (NB10) and Ni-Al-MoS2-Ag-Cr2O3–7.5 wt% h-BN (NB7.5 + 7 wt% Cr2O3) against Al2O3 ball in an operative testing regime from (RT-800 °C) using ball-on-disc tribometer. Results indicated that NB7.5+ 7 wt% Cr2O3 coating exhibited remarkable self-lubricating and wear resistance properties as compared to other coatings. However, NB7.5+ 7 wt% Cr2O3 revealed slightly higher coefficient of friction (COF) in compare to NB7.5 coating till 400 °C, and beyond that it showed a decreasing trend and lesser COF in compare to other coatings. The observed wear mechanisms at different temperatures were discussed in detail after analyzing the morphologies of worn surface. The pivotal role played by the participating solid lubricants were also discussed in detail which help in to provide the continuous compacted layers at the worn surfaces at elevated temperature.

Microstructure and properties analysis of Ni60-based/WC composite coatings prepared by laser cladding

In this study, Ni60-WCx coatings (x = 0, 2, 4, 6 %) on 316L stainless steel (316Lss) were prepared via laser cladding technology. We examined all specimens s for microstructure, phase composition, microhardness and electrochemistry using several characterization techniques. It shows that the microstructure of the Ni-based coatings can be changed with WC powder. When the WC ratio is 2 %, crystalline crystals and cellular crystals can be found in the coating. As the WC ratio increases, more cellular crystals and fewer spiny crystals appear in the coating. When the WC ratio changes to 6 %, only cellular crystals can be found in the coating. The microhardness resultsshow that the Ni-based overcoat with added WC has a better microhardness compared to the pure Ni coating, and its average value of the coating area reaches a maximum value of 822.8 HV at a WC ratio of 2 %. That is due to the addition of WC which can cause regime transition. In addition, the Ni-based coating has better corrosion properties due to its different microstructure. When the WC ratio is 2 %, the specimen possesses the maximum Ecorr and smaller icorr with the best corrosion resistance.

Stress Distribution in Wear Analysis of Nano-Y2O3 Dispersion Strengthened Ni-Based μm-WC Composite Material Laser Coating.

Oxide-dispersion- and hard-particle-strengthened (ODS) laser-cladded single-layer multi-tracks with a Ni-based alloy composition with 20 wt.% μm-WC particles and 1.2 wt.% nano-Y2O3 addition were produced on ultra-high-strength steel in this study. The investigation of the composite coating designed in this study focused on the reciprocating friction and wear workpiece surface under heavy load conditions. The coating specimens were divided into four groups: (i) Ni-based alloy, nano-Y2O3, and 2 μm-WC (2 μm WC-Y/Ni); (ii) Ni-based alloy with added 2 μm-WC (2 μmWC/Ni); (iii) Ni-based alloy with added 80 μm-WC (80 μmWC/Ni); and (iv) base metal ultra-high-strength alloy steel 30CrMnSiNi2A. Four conclusions were reached: (1) Nano-Y2O3 could effectively inhibit the dissolution of 2 μm-WC. (2) It can be seen from the semi-space dimensionless simulation results that the von Mises stress distribution of the metal laser composite coating prepared with a 2 μm-WC particle additive was very uniform and it had better resistance to normal impact and tangential loads than the laser coating prepared with the 80 μm-WC particle additive. (3) The inherent WC initial crack and dense stress concentration in the 80 μm-WC laser coating could easily cause dislocations to accumulate, as shown both quantitatively and qualitatively, resulting in the formation of micro-crack nucleation. After the end of the running-in phase, the COF of the 2 μm-WC-Y2O3/Ni component samples stabilized at the minimum of the COF of the four samples. The numerical order of the four COF curves was stable from small to large as follows: 2 μm-WC-Y2O3/Ni, 2 μm-WC/Ni, 80 μm-WC/Ni, and 30CrMnSiNi2A. (4) The frictional volume loss rate of 2 μm-WC-Y2O3/Ni was 1.3, which was significantly lower than the corresponding values of the other three components: 2.4, 3.5, and 13.