Cold Gas Dynamic Spray Research Articles

Obtaining electrically conductive wear-resistant coatings using cold gas-dynamic spraying method

This work presents research results of the technology development in applying electroconductive wear-resistant coatings using supersonic cold gas-dynamic spraying method.

Understanding the process of installing Al + Al2O3 powder coatings by cold gas dynamic spraying on substrates with different surface roughness

The present research paper aims to study the process of gas-dynamic cold spray at low pressure. The influence of surface roughness of substrate aluminum alloy A7 on the sprayed coatings porosity is also researched. The developed powder mixture A-10-1 (Al + 79.3% Al2O3) was used as the sprayed material. The samples surface was subjected to abrasive treatment, after that the surface roughness was evaluated using a profilometer with an estimate of the microroughness Ra ranging from 0.4 μm to 1.5 μm. The coating process was sprayed by the low-pressure cold spraying method using the DIMET 405. The working gas is compressed air, which is heated to 450 оC and accelerated by pressure. The heated flow of gas and powders impact to substrate and make a deposition. As a result of studying of the obtained coating’s microstructure by the metallographic method using SEM was found that the porosity in the sprayed coating is not low, reaches values from 0.56 to 0.89%, and rises along with increasing of surface roughness of the substrate during the coating process of A-10-1 powder mixture. The size of the pores ranging from 1 μm to 15 μm. Moreover, the orientation of the substrate roughness does not affect the quality of the coatings. The efficiency of cold spraying by the low-pressure method is measured. Due to the low contact speed and temperature during spraying, the deposition efficiency is low, in criminating to 5%.

PROCESSES AND TECHNOLOGIES OF COLD GAS DYNAMIC SPRAYING OF AGRICULTURAL EQUIPMENT

The article is devoted to the technology of cold gas-dynamic spraying - a relatively new technology for creating functional coatings in which narrowed-expanding nozzles (De Laval nozzles) are used, in which solid powders are sprayed at or close to supersonic speed in the direction of the substrate, where they plastically deform and adhere. Cold gas dynamic spraying is an innovative process that has received widespread scientific interest and industrial applications in the automotive, aerospace and biotechnology industries in recent years. Spraying various powder materials in this way provides protection against corrosion and can increase the mechanical strength and wear resistance of details. With that method it is possible to create functional coatings with different thermal conductivities and electrical conductivities, which can be used as insulation materials, conducting and isolation surface layers of parts, coatings for controlling gaps, restoring and repairing details. The article discusses modern developments in the field of experimental analysis of technologies and processes of cold gas-dynamic spraying, the systems of cold gas-dynamic spraying and coating formation are determined and the parameters and principles of the process are described. The installation for spraying surfaces developed at VNAU is presented and researches and the analysis of possibility of use of a method of a cold gas-dynamic spraying for restoration of details of autotractor equipment of agricultural purpose are carried out.

INVESTIGATION OF THE SPEED OF MOVEMENT OF COLD GAS DYNAMIC SPRAYING POWDER PARTICLES

The article shows the results of the study of the velocity of the sprayed powder particles on the example of cold gas-dynamic spraying of copper powder C01-11. Features and advantages of gas-dynamic spraying before other gas-thermal coating methods are given. The importance of the speed regime of coating and its influence on the formation of the coating is analyzed. A computational experimental method for determining the velocity of sprayed particles is proposed, as well as an experimental setup with the help of which it is possible to obtain objective data on the velocity regime of cold gas-dynamic coating. The design of the applied gas-dynamic spraying device is shown, which contains an electric heater of the compressed air flow and an accelerator of the heated compressed air into which the sprayed metal powder is driven due to the ejection effect. An experimental setup was used for the study, which contained two rotating disks mounted at a distance of 20 mm from each other on the shaft of a high-speed electric motor, with holes in the upper disk through which spraying occurs on the surface of the lower disk. Due to the fact that the disks with the spraying process rotate at a speed of 10587 rpm is the displacement of the sputtering figure on the lower disk relative to the projection of the hole of the upper disk on the lower disk. The magnitude of this displacement is calculated by the velocity of the particles of the sprayed powder, according to the above method. The parameters that are taken into account when calculating the speed of the spray particles of the powder is the diameter of the nozzle of the spray device 5 mm. The distance from the nozzle cut to the upper disk is 10 mm. The distance from the nozzle cut to the lower disk is 32 mm. The distance between the disks a = 22 mm. The radius on which the nozzle of the spray device is installed is 90 mm. As a result of the experiments, it was found that when spraying copper powder C01-11 at a temperature of 20 ºC, the spraying speed is 232.2 m / s, which does not provide conditions for coating, and at elevated temperatures to 285 ºC quality coating was formed. The spraying speed was from 302.7 to 359.2 m / s for critical sections of 2.5 and 3.01 mm2, and the spraying area at higher speeds was approximately 20% higher than at lower speeds. This makes it possible for researchers to determine the velocity modes of spraying and, accordingly, to more accurately assign the optimal technological parameters to achieve the highest quality results of creating functional coatings.

Preparation of the Composite Powder Al – B4C by Ball Milling for Cold Spray

In the work, when ball milling of mixture of aluminum powder (ASD – 1) and boron carbide (F 500) powder in a high-energy planetary mill, composite particles sized from 10 to 100 microns were produced, in the volume of which ultrafine boron carbide particles were distributed in the size range from 0.1 to 20 microns. It is assumed that the use of such particles in the production of coatings by cold gas-dynamic spraying will increase the deposition efficiency and the weight fraction of boron carbide in the coating. An increase in the concentration of carbide particles in the processed powder mixture, under all other conditions being equal, leads to a decrease in the average volume size of the particles. It is noted that in this case, the boron carbide particles behave as a surfactant. The X-ray phase analysis has shown diffraction peaks corresponding only to aluminum and boron carbide, therefore, under the selected milling conditions, the phase composition remain the same as in the original powders.

Effect of Hot Isostatic Pressing on the Structure and Properties of Articles from Alloy VT6 Obtained by Cold Gas-Dynamic Spraying

Effect of Hot Isostatic Pressing on the Structure and Properties of Articles from Alloy VT6 Obtained by Cold Gas-Dynamic Spraying

Deposition of Brass Coating by a Method of Cold Gas-Dynamic Spraying

Deposition of Brass Coating by a Method of Cold Gas-Dynamic Spraying

Cold Gas-Dynamic Spray for Catalyzation of Plastically Deformed Mg-Strips with Ni Powder.

Magnesium hydride (MgH2) has received significant attention due to its potential applications as solid-state hydrogen storage media for useful fuel cell applications. Even though MgH2 possesses several attractive hydrogen storage properties, it cannot be utilized in fuel cell applications due to its high thermal stability and poor hydrogen uptake/release kinetics. High-energy ball milling, and mechanically-induced cold-rolling processes are the most common techniques to introduce severe plastic deformation and lattice imperfection in the Mg/MgH2. Furthermore, using one or more catalytic agents is considered a practical solution to improve both the de-/rehydrogenation process of MgH2.These treatments are usually dedicated to enhance its hydrogen storage properties and deduce its thermal stability. However, catalyzation of Mg/MgH2 powders with a desired catalytic agent using ball milling process has shown some disadvantages due to the uncontrolled distribution of the agent particles in the MgH2 powder matrix. The present study has been undertaken to employ a cold gas-dynamic spray process for catalyzing the fresh surfaces of mechanically-induced cold-rolled Mg ribbons with Ni powder particles. The starting Mg-rods were firstly heat treated and forged 200 times before cold rolling for 300 passes. The as-treated ribbons were then catalyzed by Ni particles, using cold gas-dynamic spray process. In this catalyzation approach, the Ni particles were carried by a stream of Ar gas via a high-velocity jet at a supersonic velocity. Accordingly, the pelted Ni particles penetrated the Mg-substrate ribbons, and hence created numerous micropores into the Mg, allowed the Ni particles to form a homogeneous network of catalytic active sites in Mg substrate. As the number of coating time increased to three times, the Ni concentration increased (5.28 wt.%), and this led to significant enhancement of the Mg-hydrogen storage capacity, as well as improving the de-/rehydrogenation kinetics. This is evidenced by the high value of hydrogen storage capacity (6.1 wt.% hydrogen) and the fast gas uptake kinetics (5.1 min) under moderate pressure (10 bar) and temperature (200 °C). The fabricated nanocomposite MgH2/5.28 wt.% Ni strips have shown good dehydrogenation behavior, indicated by their capability to desorb 6.1 wt.% of hydrogen gas within 11 min at 200 °C under 200 mbar of hydrogen pressure. Moreover, this system possessed long cycle-life-time, which extended to 350 h with a minimal degradation in the storage and kinetics behavior.

Fused Filament Fabrication of ONYX-Based Composites Coated with Aluminum Powders: a Preliminary Analysis on Feasibility and Characterization

Polymer-based AM methods are the most mature additive technologies for their versatility and variety of products obtainable. The addition of fibre reinforcement can also confer to the manufactures produced good mechanical properties. Unfortunately, several applications are still precluded because polymers cannot guarantee appropriate electrical conductivity, erosion resistance and operating temperature. Aiming to overcome these issues, the metallization of the surfaces emerges as a possible solution. Unfortunately, thermoplastic polymers exhibit thermosensitive behaviour and run the risk of being damaged when traditional metallization techniques, which require the melting of metal powders which will act as a protective coating. For this reason, studies have focused on Cold Gas Dynamic Spray, an additive manufacturing technology, which exploits kinetic energy to favour the adhesion of metal particles rather than the increase in temperature. In this work, a first attempt is made to verify the feasibility of cold spray coatings on 3D printed composite substrates, produced by means of Fused Filament Fabrication (FFF) technique. FFF technology allows the deposition of two different types of filaments by using a double extruder. These composite fibres within 3D printed parts manage to give the object a resistance comparable to that of a metal part with lower production cost and a high degree of automation. These structures, made of ONYX, a Nylon matrix in which short carbon fibres are dispersed, and reinforced with long carbon fibres, are designed to better fit the CS deposition. Aluminium coatings have been produced and a characterization campaign has been carried on.

CREATION OF COMPOSITE ELECTRICALLY CONDUCTIVE COATINGS BY GAS DYNAMIC SPRAYING

The article presents the results of research of spraying processes of composite electrically conductive coatings using copper C01-11 and aluminum A20-11 powders in order to determine the effect of components on each other in the formation of cold gas-dynamic spraying (CGDS) and the development of recommendations for the introduction of additional component to obtain a composite coating with a given ratio of different components. For example, when at a working air temperature of 300 ° C the copper sputtering coefficient is almost zero, it is a search for the experimental dependence of the sputtering coefficient change depending on the percentage of components of copper and aluminum powders in the sprayed mixture and determination of their residual content in the coating. based on the obtained data of the sputtering coefficients of copper and aluminum. The CGDS method obtained blanks with composite coatings from mixtures of powders of aluminum A20-11 and copper C01-11 at different initial concentrations of aluminum by weight (from 0 to 100% with a step of 10%) under otherwise equal conditions (air pressure 0,6 MPa, temperature air heating 300 ° C). The sputtering coefficient of a mixture of copper and aluminum and the residual content of components in the sprayed composite coatings were found. Data on the residual content of the individual components in the sprayed coating allows to determine the composition of the source powder required for spraying a given content of each of the components in the coating. The dependences of the spraying coefficients of copper C01-11 and aluminum A20-11 on the mass content of aluminum in the sprayed mixture were found. When the initial concentration of aluminum is less than 66%, the coefficient of copper deposition is greater than the coefficient of deposition of aluminum. Both increase with increasing concentration of aluminum until it reaches 61%. At high concentrations of aluminum (more than 66%) the spray coefficients of copper, aluminum and their mixtures coincide. The results obtained on the residual content of the components in the coating allow you to select the composition of the source powder required to obtain the desired content of components in the coating. For example, the maximum residual copper content (~ 95%) can be obtained by adding 30-40% aluminum to the starting powder. The obtained results prove the influence of the components on each other and justify the amount of introduction of an additional component for spraying a composite coating containing a component that is difficult to spray.

INVESTIGATION OF THE SPEED OF MOVEMENT OF POWDER PARTICLES OF COLD GAS DYNAMIC SPRAYING

The article shows the results of the study of the velocity of the sprayed powder particles on the example of cold gas-dynamic spraying of copper powder C01-11. Features and advantages of gas-dynamic spraying before other gas-thermal coating methods are given. The importance of the speed regime of coating and its influence on the formation of the coating is analyzed. A computational experimental method for determining the velocity of sprayed particles is proposed, as well as an experimental setup with the help of which it is possible to obtain objective data on the velocity regime of cold gas-dynamic coating. The design of the applied gas-dynamic spraying device is shown, which contains an electric heater of the compressed air flow and an accelerator of the heated compressed air into which the sprayed metal powder is driven due to the ejection effect. An experimental setup was used for the study, which contained two rotating disks mounted at a distance of 20 mm from each other on the shaft of a high-speed electric motor, with holes in the upper disk through which spraying occurs on the surface of the lower disk. Due to the fact that the disks with the spraying process rotate at a speed of 10587 rpm is the displacement of the sputtering figure on the lower disk relative to the projection of the hole of the upper disk on the lower disk. The magnitude of this displacement is calculated by the velocity of the particles of the sprayed powder, according to the above method. The parameters that are taken into account when calculating the speed of the spray particles of the powder is the diameter of the nozzle of the spray device 5 mm. The distance from the nozzle cut to the upper disk is 10 mm. The distance from the nozzle cut to the lower disk is 32 mm. The distance between the disks a = 22 mm. The radius on which the nozzle of the spray device is installed is 90 mm. As a result of the experiments, it was found that when spraying copper powder C01-11 at a temperature of 20 ºC, the spraying speed is 232.2 m / s, which does not provide conditions for coating, and at elevated temperatures to 285 ºC quality coating was formed. The spraying speed was from 302.7 to 359.2 m / s for critical sections of 2.5 and 3.01 mm2, and the spraying area at higher speeds was approximately 20% higher than at lower speeds. This makes it possible for researchers to determine the velocity modes of spraying and, accordingly, to more accurately assign the optimal technological parameters to achieve the highest quality results of creating functional coatings.

Comparison of Performance and Microstructure of Two Kinds of Cold Spray Anticorrosion Composite Coatings on High-strength Steel

Objective to study the performance of Zn/Ni composite coatings and Al/Zn composite coatings, which were deposited by Cold Gas Dynamic Spray. Methods: Those coatings was sprayed by Zn and Ni mixture powder and Al and Zn mixture powder on 300M high-strength steel surface, the SEM images and micro hardness tester analyzed the two kinds coatings’ morphology and microstructure. The corrosion resistance of Zn/Ni coatings can be compare with Al/Zn coatings, which was investigated by neutral salt-spray test and coating furcated test. Results The results indicate that Zn/Ni coatings porosity is 0.8%, it is same as Al/Zn coatings. The micro hardness of Zn/Ni coatings is 70.8HV, which is higher than Al/Zn coatings 61.2HV. However, the salt spray result of Al/Zn coatings can reach 1000h and it can reach 770h even the coatings fails; which is better than Zn/Ni coatings, their salt spray resistance can reach 770h and it can reach 350h when the coatings fails. Conclusion those coatings could both be efficient corrosion resistance coatings on 300M high strength steel surfaces.

Investigation of calcium–magnesium-alumino-silicate (CMAS) resistance and hot corrosion behavior of YSZ and La2Zr2O7/YSZ thermal barrier coatings (TBCs) produced with CGDS method

Thermal barrier coatings (TBCs) commonly expose to oxidation, hot corrosion, and CaO-MgO-Al2O3-SiO2 (CMAS) attacks during the service condition. All of these attacks cause the spallation or delamination of TBCs from the bond coat. In this study, the effect of these attacks on YSZ and La2Zr2O7/YSZ TBC systems was investigated. YSZ and double layer La2Zr2O7/YSZ topcoats were deposited using electron beam physical technique (EB-PVD) on CoNiCrAlY bond coat produced by cold gas dynamic spray (CGDS) technique. CMAS tests at 1225 °C for 4, 8, 12, 16, 20, 24, 28, and 32 h and 5 h cyclic hot corrosion tests at 1000 °C were carried out on TBCs. Before and after the tests, TBCs were characterized using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), x-ray diffraction (XRD) and image analysis software program. At the end of the tests, the formed phases, microstructural changes, and general failure mechanisms were investigated in detail for each test. The general result shows that double-layered TBCs provide significant contributions and durability against high-temperature corrosive attacks of conventional YSZ TBC. In addition, in this study, hot corrosion damage mechanism and CMAS attack significantly damaged the column morphology of the EB-PVD method, reducing the thermal insulation properties and strain tolerance of TBCs. As a result of the tests, spallation and phase changes occurred in the damaged TBC systems.

Study of phase transformations in the synthesis of catalytic coatings on metal carrier

The article presents the results of a study of the catalytically active system Ni-Al-Al(OH)3-Ca(OH)2-Mg(OH)2 for efficient synthesis gas production. A technology for obtaining volumetric porous functional coatings has been developed using the method of supersonic cold gas-dynamic spraying. The advantages of this method and its possibilities from the point of view of producing synthesis gas with high activation energy are shown.

Development of an alloy in the tellurium - copper - cerium system for manufacturing functional coatings for photocathodes of photoelectronic devices

This paper presents the results on the development of an alloy in the tellurium - copper - cerium system used for the manufacture of functional coatings using the technologies of supersonic cold gas-dynamic spraying. Coatings from the specified alloy are used for the manufacture of photocathodes of photoelectronic devices operating in the UV spectral region.

A numerical analysis of compressive residual stresses in cold gas dynamic spray (CGDS) deposition method

This study presents a finite element approach of a numerical model to investigate the profile of the deformed sprayed particles and the compressive residual stresses analysis at the interfacial zone of particle and substrate impact using cold gas dynamic spray (CGDS). The Lagrangian approach was used to analyze, in details, the material deformation behavior during impact, contact problems of single-particle impact process and the outputs of equivalent plastic strain and temperature to achieve a qualitative understanding of cold gas dynamic spray contact process of cold sprayed particle on the substrate. The evolution of residual compressive stresses during impact was also analyzed for multiple-particles impact process using the Lagrangian approach. It can be observed that the compressive residual stresses increase by increasing the preheating temperature and particle initial impact velocity.

A numerical analysis of compressive residual stresses in cold gas dynamic spray (CGDS) deposition method

This study presented a finite element approach of a numerical model to investigate the profile of the deformed sprayed particles and the compressive residual stresses analysis at the interfacial zone of particle and substrate impact using cold gas dynamic spray (CGDS). Elastic, isotropic hardening and Johnson-Cook material model were selected to account for elasticity, plasticity and stress softening behaviour of the ductile materials as the material model formulations respectively. The Lagrangian approach was used to analyze in detail the material deformation behaviour during impact, contact problems of single-particle impact process and the outputs of equivalent plastic strain and temperature to achieve a qualitative understanding of cold gas dynamic spray contact process of cold sprayed particle on the substrate. The evolution of residual compressive stresses during impact was also analyzed for multiple-particles impact process using the Lagrangian approach. It can be observed that the compressive residual stresses increase by increasing the preheating temperature and particle initial impact velocity.

Atomistic simulation of the preheating treatment and crystal orientation influences in the hardness of cold gas dynamic sprayed nickel coating unto the copper substrate

Abstract As a modern surface modification technique, cold gas dynamic spray (CGDS) is commonly used to improve the quality of the surface. Molecular dynamics (MD) simulations were used to systematically analyse the effects of preheating treatment and crystal orientation of copper (Cu) substrate on coating surface generation mechanisms by nickel (Ni) particles in the cold gas dynamic spray. In this study, the embedded-atom method (EAM/alloy) potential was adopted to describe the interaction of Ni atoms in the particle and Cu atoms in the substrate. The amorphization tendency and temperature distribution in our simulation are consistent with the experimental results from the literature. Simulation results show that the particle/substrate impact in the interfacial region undergoes a structural transformation from the face-centred cubic structure into different local atomic structure upon the impact of the Ni particle. After the impact, recrystallization of the crystal lattice occurs and due to unrecoverable plastic deformation, the substrate surface is residually dimpled. Comparing the hardness of three different crystal orientation of Cu surface, it is obvious that [1 1 0] is the hardest surface and the [1 0 0] the weakest. With regard to the effect of preheating temperatures, simulation results show that Cu substrate softens, and Cu adhesiveness increases when preheating temperature is higher.

Nanoindentation study in cold gas dynamic sprayed thin films using molecular dynamics simulation

Abstract To enhance the efficiency of the cold gas dynamic spray (CGDS) technology-based metal composite membrane, it is extremely important to examine the mechanical characteristics of the CGDS coated thin films at the atomistic level. The nanoindentation test was performed in the present study on vanadium, copper and palladium thin film coated on niobium substrate by using molecular dynamic (MD) simulation. At the indentation region, the thermosetting control is applied with temperature variance from 300 K to 700 K. The results show that as the temperature decreases, the indentation load increases for loading and unloading processes. nanoindentation test was also performed at a different nanoindentation loading rate of 0.5–2.5 A/ps. The measured average hardness of the thin films by nanoindentation method increases in the order of vanadium, copper and palladium with the nanoindentation loading rate.

Technological parameters of gas-dynamic spraying affecting the formation coating based on mixture of particles copper, zinc and corundum

The results of a study of the effect of the spraying temperature and the overlap coefficient on the formation of the coating structure based on a mixture of Cu, Zn and Al2O3 particles applied by cold gas-dynamic spraying are presented. X-ray diffraction analysis has shown a decrease in the size of coherent scattering regions (CSR) from 200 nm to 90 nm for copper and to 64 nm for zinc when using an overlap coefficient of 55 % and more significant (up to 22 nm) with an overlap of 64 %. The CSR sizes of electronic type compounds CuZn3 (ε-phase) and Cu5 Zn8 (γ-phase) are quite close to the CSR size of zinc. The microdeformation of copper decreases from 187 to 119 % with an increase in the deposition temperature and does not depend on the overlap coefficient. For the electronic compound of the ε-phase, the microstrain value increases, and the γ-phase decreases by 2 times (from 0.31 to 0.17 %). The mass fraction of aluminum oxide (corundum) decreases from 5.4 to 2.2 % with an increase in the spraying temperature. The use of the maximum spraying temperature of 450 °C is accompanied by the formation of zinc oxide, the mass fraction of which is 4.3 % with 64 % overlap.