초음속 저온분사법에 의한 알루미늄 분말 적층에서 얇은 모재에 발생하는 변형에 대한 연구

이재철(Jae-Chul Lee),천두만(Doo-Man Chun),김성근(Sung-Geun Kim),안성훈(Sung-Hoon Ahn) 한국정밀공학회 2006 한국정밀공학회 학술발표대회 논문집 Vol.2006 No.5월

Cold gas dynamic spray or cold-spray is a deposition process, which causes deformation of a thin substrate. The deformation is usually convex to the deposited side. In this research, the main cause of the deformation was investigated using 6061-T6 aluminum alloy. The effects of anisotropic coefficient of thermal expansion (CTE) of the deposited layer by cold-spray and residual stress were studied by experiments and finite element analysis. The Hole Drilling method was applied to measure residual stress in the cold-spray layer and substrate. The data obtained by the experiments were used for the analysis of substrate deformation. From the result of the analysis, it was concluded that compressive residual stress was the main reason of substrate deformation while CTE had little effect.

저온 분사 공정으로 제조된 티타늄 코팅층의 치밀화에 미치는 열처리 분위기의 영향

유지상,김형준,오익현,이기안,Yu, Ji-Sang,Kim, Hyung-Jun,Oh, Ik-Hyun,Lee, Kee-Ahn 한국분말야금학회 2012 한국분말재료학회지 (KPMI) Vol.19 No.2

This study investigated the effects of annealing environment for the densification and purification properties of pure titanium coating layer manufactured by cold spraying. The annealing was conducted at $600^{\circ}C$/1 h and three kinds of environments of vacuum, Ar gas, and $5%H_2+Ar$ mixture gas were controlled. Cold sprayed Ti coating layer (as sprayed) represented 6.7% of porosity and 228 HV of hardness, showing elongated particle shapes (severe plastic deformation) perpendicular to injection direction. Regardless of gas environments, all thermally heat treated coating layers consisted of pure ${\alpha}$-Ti and minimal oxide. Vacuum environment during heat treatment represented superior densification properties (3.8% porosity, 156.7 HV) to those of Ar gas (5.3%, 144.5 HV) and $5%H_2+Ar$ mixture gas (5.5%, 153.1 HV). From the results of phase analysis (XRD, EPMA, SEM, EDS), it was found that the vacuum environment during heat treatment could be effective for reducing oxide contents (purification) in the Ti coating layer. The characteristic of microstructural evolution with heat treatment was found to be different at three different gas environments. The controlling method for improving densification and purification in the cold sprayed Ti coating material was also discussed.

Cold spray induced amorphization at the interface between Fe coatings and Al substrate

Ko, K.H.,Choi, J.O.,Lee, H.,Seo, Y.K.,Jung, S.P.,Yu, S.S. Elsevier 2015 Materials letters Vol.149 No.-

<P><B>Abstract</B></P> <P>Cold spraying of hard Fe particles onto soft Al substrates increases the mechanical energy supplied to the interface of the two metals compared to previous Al coatings on Fe substrate. As a result, the irregular interfacial morphologies found in this study were on a larger scale. As in the case of the soft particle/hard substrate system, roll-up features that perfectly encapsulated the Fe particles were found, but their structure was larger and complicated. When the Fe/Al interface was investigated further, it was found to be amorphous. This amorphous layer had a composition gradient, which indicates intermixing on an atomic scale. As could be expected from the enhanced mechanical energy of the Fe particle/Al substrate system, the amorphous layer was also thicker than that of the reversed system. Cold spraying is an ambient-temperature processing technique that involves materials that can be plastically deformed, and therefore, an analogy can be found with the cold rolling (cold welding) of two metal sheets or wires, where similar interfacial characteristics are found. Hence, the mechanisms of bonding and interface formation can be thought of as similar.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The Al substrate was coated with an Fe feedstock by cold spray. </LI> <LI> The roll-up features were increased with some forming complicated 3-D structures. </LI> <LI> The amorphous layer was also thicker than that of the reversed system. </LI> <LI> This layer had a composition gradient, which indicates intermixing on atomic scale. </LI> </UL> </P>

Chemical interaction and activation phenomena in cold-sprayed Cu particles on Sn substrate

Ko, Kyung Hyun,Lee, H.,Jung, Sang-Hyun,Ahn, Byungmin Elsevier 2018 Materials letters Vol.215 No.-

<P><B>Abstract</B></P> <P>For the interactions at the interfaces of cold sprayed particles/substrates, the formation of intermetallic compounds (IMCs) of cold-sprayed Cu particles on a Sn substrate was investigated. Under room-temperature spray conditions, intermetallic layers (Cu<SUB>6</SUB>Sn<SUB>5</SUB>) were formed at the interfaces because of the high velocity collisions of the Cu particles. For the chemical interaction and activation phenomena, including intermixing at the interfaces, the bonding mechanism of the cold-sprayed coatings involved interlocking of the sprayed particles on the blasted substrates, as well as interactions between the particles and the substrate due to the high-velocity collisions (intermixing → particles’ interaction).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Interactions between cold-sprayed Cu particles and Sn substrate were demonstrated. </LI> <LI> Under room-temperature conditions, the intermetallic layers (Cu<SUB>6</SUB>Sn<SUB>5</SUB>) were formed. </LI> <LI> The formation of Cu<SUB>6</SUB>Sn<SUB>5</SUB> was resulted from intermixing and chemical interaction. </LI> </UL> </P>

냉시동 조건에서 디젤연료의 온도에 따른 유동 및 분무특성 변화

신주곤 ( Jugon Shin ),박현욱 ( Hyunwook Park ),배충식 ( Choongsik Bae ) 한국액체미립화학회 2016 한국액체미립화학회 학술강연회 논문집 Vol.2016 No.-

With the increasing use of diesel engines, emission regulations continuously become stringent such as particulate matter and nitrogen oxides as well as carbon dioxide. Issues related to the emission problem in diesel engines are represented seriously under cold-start conditions. Flow and spray characteristics of diesel fuel could be also problems under cold-start conditions, because fuel properties such as viscosity and density are changed by fuel temperature, especially at low ambient conditions. In this research, the effect of diesel fuel temperature on the flow and spray behavior under cold-start conditions was studied. The flow and spray characteristics of diesel fuel were investigated for injection rate using Bosch tube method and liquid-phase fuel penetration using Mie scattering in a constant volume combustion chamber, respectively. The injection quantity decreased at the same injection duration because of the increase fuel viscosity, as the fuel temperature deceased from 293 K to 253 K. In addition, the liquid-phase fuel penetration was longer by attenuating fuel evaporation due to low fuel and ambient temperature, and the spray angle was smaller especially in the initial stage of diesel fuel injection as well. The decrease of evaporation of injected fuel inside the chamber made the liquid-phase fuel penetration last longer. These results mean that the low fuel and ambient temperature have a negative effect on air-fuel mixing process.

저온 분사 티타늄 코팅층의 특성 및 적층 거동에 미치는 분말 형상과 분말 예열의 영향

황재남,이명주,김형준,오익현,이기안,Hwang, Jae-Nam,Lee, Myeong-Ju,Kim, Hyung-Jun,Oh, Ik-Hyun,Lee, Kee-Ahn 한국분말야금학회 2012 한국분말재료학회지 (KPMI) Vol.19 No.5

Cold spray deposition using Titanium powder was carried out to investigate the effects of powder morphology and powder preheating on the coating properties such as porosity and hardness. The in-flight particle velocity of Ti powder in cold spray process was directly measured using the PIV (particle image velocimetry) equipment. Two types of powders (spherical and irregular ones) were used to manufacture cold sprayed coating layer. The results showed that the irregular morphology particle appeared higher in-flight particle velocity than that of the spherical one under the same process condition. The coating layer using irregular morphology powder represented lower porosity level and higher hardness. Two different preheating conditions (no preheating and preheating at $500^{\circ}C$) were used in the process of cold spraying. The porosity decreased and the hardness increased by conducting preheating at $500^{\circ}C$. It was found that the coating properties using different preheating conditions were dependent not on the particle velocity but on the deformation temperature of particle. The deposition mechanism of particles in cold spray process was also discussed based on the experimental results of in flight-particle velocity.

Manufacturing and Macroscopic Properties of Cold Sprayed Cu-Ga Coating Material for Sputtering Target

Jin, Young-Min,Jeon, Min-Gwang,Park, Dong-Yong,Kim, Hyung-Jun,Oh, Ik-Hyun,Lee, Kee-Ahn The Korean Powder Metallurgy Institute 2013 한국분말재료학회지 (KPMI) Vol.20 No.4

This study attempted to manufacture a Cu-Ga coating layer via the cold spray process and to investigate the applicability of the layer as a sputtering target material. In addition, changes made to the microstructure and properties of the layer due to annealing heat treatment were evaluated, compared, and analyzed. The results showed that coating layers with a thickness of 520 mm could be manufactured via the cold spray process under optimal conditions. With the Cu-Ga coating layer, the ${\alpha}$-Cu and $Cu_3Ga$ were found to exist inside the layer regardless of annealing heat treatment. The microstructure that was minute and inhomogeneous prior to thermal treatment changed to homogeneous and dense with a more clear division of phases. A sputtering test was actually conducted using the sputtering target Cu-Ga coating layer (~2 mm thickness) that was additionally manufactured via the cold-spray coating process. Consequently, this test result confirmed that the cold sprayed Cu-Ga coating layer may be applied as a sputtering target material.

전단동축형 분사기들의 미립화 특성에 대한 연구

안종현 ( Jonghyeon Ahn ),이근석 ( Keunseok Lee ),안규복 ( Kyubok Ahn ) 한국분무공학회 2021 한국액체미립화학회지 Vol.26 No.1

Six shear coaxial injectors with different recess length and taper angle were manufactured. Cold-flow tests on the injectors were performed at room temperature and pressure using water and air as simulants. By changing the water mass flow rate and air mass flow rate, spray images were taken under single-injection and bi-injection. Breakup length and spray angle were analyzed from instantaneous and averaged spray images using image processing techniques. For all the injectors, the breakup length generally decreased as the momentum flux ratio increased at the same gas mass flow rate. The injectors with 7.5° taper angle usually had the longest breakup length and the smallest spray angle. When the taper angle was 15° or more, it hardly affected breakup length and spray angle. The recess length did not influence breakup length but its effect on spray angle depended on the taper angle.

리세스 길이 및 분사압력 변이에 따른 스월 동축형 인젝터의 분무특성

배성훈(Seong Hun Bae),권오채(Oh Chae Kwon),김정수(Jeong Soo Kim) 한국추진공학회 2016 한국추진공학회지 Vol.20 No.4

This research is carried out for the performance evaluation of the injector that is one of the critical components of bipropellant-rocket-engine. Spray characteristics are investigated in detail according to the recess length and injection pressure on the swirl-coaxial-injector using gaseous methane and liquid oxygen as propellants. A visualization is conducted by the Schlieren photography that is composed of a light source, concave mirrors, knife, and high-speed-camera. A hollow-cone-shape is identified in the liquid spray that is spread only by inner injector and the spray angle is decreased due to the diminution of swirl strength in accordance with the increase of the length of injector orifice. When the injector sprays the liquid through the inner injector with the aid of gas through the outer injector, the spray angle in external mixing region tends to increase with rise of the recess length, while in internal mixing region, it is decreased. It is also confirmed that the same tendency of the spray angle with recess length appears irrespective of the injection pressure of liquid spray.

Enhancing Tensile Properties of Wire-Arc Additively Manufactured Ti-6Al-4 V Deposits Via Cryogenic Vaporised Ar Shielding/Cooling

Peng Han,Jia Lin,Wen Wang,Zhihao Liu,Yating Xiang,Ting Zhang,Qiang Liu,Xiaohu Guan,Ke Qiao,Yingchun Xie,Kuaishe Wang 대한금속ᆞ재료학회 2023 METALS AND MATERIALS International Vol.29 No.2

The high-entropy alloy particles reinforced 6061Al composite was prepared by cold spray (CS) and then modified by frictionstir processing (FSP). The microstructure evolutions, corrosion, and wear behaviors of the composites were investigated. Results showed that numerous micro-pores and cracks were distributed in the Al matrix due to adiabatic shear instability andinsufficient deformation of the deposited particles for CSed samples. The average size of uniformly distributed HEA particleswas ~ 24 μm, and the geometric necessary dislocation (GND) density reached 17.1 × 1015m−2 due to large plastic deformationduring CS. Comparatively, the micro-pores and cracks were eliminated, and many fragmented HEA particles dispersed inthe Al matrix with an average size of ~ 4 μm for FSPed sample. Note that the GND density reduced to 9.8 × 1015m−2 due todynamic recrystallization during FSP. The formation rate of the oxide film was gradually greater than that of the dissolutionrate with the samples immersion in 3.5 wt% NaCl solution from 12 to 36 h, and the main corrosion mechanism was particledissolution around micro-pores and pitting for CSed and FSPed samples, respectively. In the polarization process, the FSPedsamples exhibited low corrosion tendency and high corrosion rate due to the dense and uniform microstructure, low GNDdensity, and dispersed HEA particles. The FSPed samples had better wear resistance than the CSed samples at 25 °C and200 °C. The dominant wear mechanisms of CSed and FSPed samples were abrasion at 25 °C, while the wear mechanismsof these samples were adhesion accompanied by abrasion at 200 °C.