Critical Deposition Condition of CoNiCrAlY Cold Spray Based on Particle Deformation Behavior
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Critical Deposition Condition of CoNiCrAlY Cold Spray Based on Particle Deformation Behavior Yuji Ichikawa1 • Kazuhiro Ogawa1
Submitted: 16 December 2015 / in revised form: 11 October 2016 / Published online: 9 December 2016 The Author(s) 2016. This article is published with open access at Springerlink.com
Abstract Previous research has demonstrated deposition of MCrAlY coating via the cold spray process; however, the deposition mechanism of cold spraying has not been clearly explained—only empirically described by impact velocity. The purpose of this study was to elucidate the critical deposit condition. Microscale experimental measurements of individual particle deposit dimensions were incorporated with numerical simulation to investigate particle deformation behavior. Dimensional parameters were determined from scanning electron microscopy analysis of focused ion beam-fabricated cross sections of deposited particles to describe the deposition threshold. From Johnson-Cook finite element method simulation results, there is a direct correlation between the dimensional parameters and the impact velocity. Therefore, the critical velocity can describe the deposition threshold. Moreover, the maximum equivalent plastic strain is also strongly dependent on the impact velocity. Thus, the threshold condition required for particle deposition can instead be represented by the equivalent plastic strain of the particle and substrate. For particle-substrate combinations of similar materials, the substrate is more difficult to deform. Thus, this study establishes that the dominant factor of particle deposition in the cold spray process is the maximum equivalent plastic strain of the substrate, which occurs during impact and deformation. Keywords cold spray deposition mechanism FIB
& Yuji Ichikawa [email protected] 1
Fracture and Reliability Research Institute, Tohoku University, Sendai, Japan
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Introduction The cold spray process—a relatively new coating technology—was initially developed in the mid-1980s at the Institute for Theoretical and Applied Mechanics of the Siberian Division of the Russian Academy of Science in Novosibirsk (Ref 1-4). This technique is based on the highvelocity (300-1200 m/s) impingement of small solid particles (generally 1-50 lm in diameter) on the substrate (Ref 3, 4). In this spraying process, the particles are accelerated by a supersonic gas jet at the heated gas temperature, which is usually lower than the melting point of the powder material. Consequently, this spraying process solved the problems of thermal spraying, i.e., oxidation and phase transformation (Ref 5, 6). Moreover, cold spraying systems are much simpler than low-pressure plasma spray (LPPS) systems. MCrAlY (where M is Co and/or Ni) is widely used for the bond-coat of thermal barrier coating (TBC) for landbased gas turbine applications. Additionally, MCrAlY is used for protection from high-temperature oxidation and hot corrosion (Ref 7, 8). Until recently, MCrAlY has been deposited by conventi
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