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Sun B.,Plasma Giken Co. | Fukanuma H.,Plasma Giken Co. | Ohno N.,Plasma Giken Co.
Surface and Coatings Technology | Year: 2014

The High-Velocity Oxy-Fuel (HVOF) technology has been widely used to deposit cermet, metals, and alloy coatings. However, the high temperature and oxidative flame jet results in oxidation and decomposition of spray particles during the spraying process; giving significant influence on phase composition, microstructure, properties, and performance of the sprayed coatings. In this paper, a high pressure HVOF system with a combustion chamber pressuring up to 3.0. MPa along with characteristics of lower flame temperature and higher flame velocity was used to deposit Stainless Steel 316L coatings. Particle velocity was measured by using the DPV-2000 system. It was found that higher combustion chamber pressure enables higher particle velocity. The influence of oxygen/fuel ratio and spray distance on deposition efficiency, coating microstructure, and microhardness of the Stainless Steel 316L was investigated. It shows that the oxygen/fuel ratio has a significant influence on particle's melting state. Therefore, dense Stainless Steel 316L coating composed of semi-molten or solid state particles can be obtained by adjusting the oxygen/fuel ratio at the combustion chamber pressure of 3.0 MPa. In the experiment, deposition efficiency up to 90% was achieved at the optimized spray conditions. As a typical conventional HVOF system of JP-5000, the comparison to the JP-5000 sprayed coating was also performed. © 2013 Elsevier B.V.


Huang R.,Plasma Giken Co. | Ma W.,Plasma Giken Co. | Fukanuma H.,Plasma Giken Co.
Surface and Coatings Technology | Year: 2014

In the cold spray process, adhesive strength between coatings and substrates is considered to be the most crucial mechanical property. Bonding is an important factor in determining if cold spray can be used for an application. Therefore, development of effective bonding between coatings with various substrates is essential to cold spray processing. In this study, Cu coatings were deposited on to three different substrates: Al5052, Al6063, and stainless steel 316. L. The adhesive strength of Cu coatings on these three substrates was investigated. The experimental results showed that effective bonding could be generated only when particle velocity exceeds 500. m/s for Al alloy substrates, and 800. m/s for stainless steel 316. L substrates. Based on the present studies, an ultra-strong bonding (more than 200. MPa) between dissimilar materials has been developed with cold spray processing. © 2014 Elsevier B.V.


Huang R.,Plasma Giken Co. | Sone M.,Plasma Giken Co. | Ma W.,Plasma Giken Co. | Fukanuma H.,Plasma Giken Co.
Surface and Coatings Technology | Year: 2015

In the cold spray process, deposition of particles takes place through intensive plastic deformation upon impact in a solid state at temperatures well below their melting point. Therefore, spray particles experience little oxidation or decomposition during this process. As a result, cold-sprayed coatings have excellent mechanical, electrical and thermal properties. In this work, pure Al, Cu, Ti and stainless steel 316 were deposited by cold spray. The tensile strength and elongation of these coatings were also measured. The results showed that the as-sprayed coatings of the four materials have poor ductility and almost no elongation. However, heat treatment can improve the mechanical properties of the cold-sprayed coatings to some extent. Here, the effects of heat treatment conditions on the mechanical properties of the four cold-sprayed materials are discussed. © 2014 Elsevier B.V.


Huang R.,Plasma Giken Co. | Fukanuma H.,Plasma Giken Co.
Proceedings of the International Thermal Spray Conference | Year: 2015

Particle velocity is one of the most crucial parameter to determine coating's properties in cold spray process, such as coating's densification and bonding strength. To achieve a high particle velocity, the common way is to increase the working gas temperature or pressure, sometime using the extremely expensive helium gas. In this study, computational fluid dynamics (CFD) method was employ to optimize the nozzle dimension in order to improve particle velocity. Particle velocity was also measured with DPV-2000 to verify the simulation results. Furthermore, coatings were deposited with the optimized nozzle, and their mechanical and electric properties were tested. The results show that the optimized nozzle benefited to improve the adhesive strength with substrate and electric properties of cold-sprayed coatings. © (2015) by ASM International All rights reserved.


Huang R.,Plasma Giken Co. | Fukanuma H.,Plasma Giken Co. | Uesugi Y.,Kanazawa University | Tanaka Y.,Kanazawa University
Journal of Thermal Spray Technology | Year: 2012

It is well known that the coating quality of plasma spraying is strongly influenced by the instability of jets in the plasma spray, which is due to arc root fluctuation. Three dimensional (3D) unsteady-state modeling was employed in this research to analyze the arc root fluctuation in a DC non-transferred plasma torch. Numerical calculations on the distributions of gas temperature and velocity in the plasma torch were carried out using argon as the plasma gas. The electrical current density and potential were also discussed. The results indicate that the fluctuation of arc inside the plasma torch is mainly induced by the movement of the arc root on the anode surface. The arc root moves downstream with the flow of gas, and simultaneously the arc is bent by electromagnetic force. When the arc bends close enough to the anode boundary, a new arc root is formed somewhere upstream of the current attachment. In this paper the nature of the arc root fluctuation is presented, and also it is demonstrated that the voltage-drop calculated is larger than that measured experimentally because the plasma inside the torch has some deviation from the local thermodynamic equilibrium state hypothesis used in the current study. © ASM International.


Sun B.,Plasma Giken Co. | Fukanuma H.,Plasma Giken Co.
Proceedings of the International Thermal Spray Conference | Year: 2012

WC-Co coatings are primarily deposited by using the high velocity oxy-fuel (HVOF) spray process. However, the decomposition and decarburization of carbides during spraying result in the degradation of coating wear performance. In this paper, a novel high pressure HVOF with the characteristics of lower particle temperature and higher particle velocity was developed. It exhibits combustion chamber pressures up to 3.0 MPa. The influence of combustion chamber pressure and oxygen/fuel equivalence ratio on WC-Co particle velocity and temperature levels were analyzed by numerical simulation. The experiment results show that the combustion chamber pressure and the oxygen/fuel equivalence ratio have a significant influence on the particle velocity and melt degrees, as well as, on the coating microstructure and microhardness. High velocity WC-Co particles in different states, i.e., molten, semi-molten and non-molten can be readily obtained by changing the spray conditions. A comparison to the conventional JP-5000 was also executed. Copyright 2012 ASM International®. All rights reserved.


Huang R.,Plasma Giken Co. | Fukanuma H.,Plasma Giken Co.
Journal of Thermal Spray Technology | Year: 2012

The adhesion mechanism of deposit/substrate interface prepared by the cold spray method is not fully understood at present. It seems that the adhesion strength is mainly determined by the mechanical (including the plastic deformation of particle and substrate) and thermal interaction between particle and substrate when the particles impact onto the substrate with a high velocity. In order to understand the adhesion mechanism, a novel adhesive strength test was developed to measure the higher bonding strength of cold sprayed coatings in this study. The method breaks through the limits imposed by glue strength in the conventional adhesive strength test, and it can be used to measure the coatings with a higher adhesive strength. The particle velocity was obtained with DPV-2000 measurement and CFD simulation. The relationships between the adhesion strength of deposits/substrate interface and particle velocity were discussed. The results show that stronger adhesion strength can be obtained with the increase of particle velocity. There are two available ways to improve the adhesion strength. One is to increase the temperature of working gas, and another is to employ helium gas as the working gas instead of nitrogen gas. © ASM International.


The object of the present invention is to provide a cold spray method in which spray efficiency is improved by using a device comprising a similar construction to the conventional ones with minor change in conditions. The cold spray method employs the nozzle for cold spray system which comprises a convergent shape part, a throat part and a conical divergent shape part widen forward from the throat part used for making the raw material powder introduce from a inlet of the nozzle which locates in the convergent shape part into and shoot the powder as a supersonic flow by using a working gas having temperature equal to or lower than a melting point of the raw material powder from a spout provided at the tip of the divergent shape part, wherein the convergent shape part is composed of a preheating region and a convergent region.


An object of the present invention is to provide a cold-spray nozzle that can be continuously used for a long time without causing clogging up of the nozzle compared to a conventional case to effectively obtain a high-quality film by a cold-spray method. To achieve the object, the cold-spray nozzle that is a convergent-divergent type cold-spray nozzle comprising a convergent part, a throat part, and a divergent part sequentially arranged in this order for constituting a working gas flow path along a working gas flow direction from an inlet side to an outlet side is employed. The inner peripheral surface of the divergent part has a conical shape and at least a part of the inner peripheral surface is constituted by a glass material.


Patent
Plasma Giken Co. | Date: 2010-12-22

An object of the present invention is to provide a cold-spray nozzle that can be continuously used for a long time without causing clogging up of the nozzle compared to a conventional case to effectively obtain a high-quality film by a cold-spray method. To achieve the object, the cold-spray nozzle that is a convergent-divergent type cold-spray nozzle comprising a convergent part, a throat part, and a divergent part sequentially arranged in this order for constituting a working gas flow path along a working gas flow direction from an inlet side to an outlet side is employed. The inner peripheral surface of the divergent part has a conical shape and at least a part of the inner peripheral surface is constituted by a glass material.

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