Integrated characterization of cold sprayed aluminum coatings

Choi, W.B.; Li, L.; Luzin, Vladimir; Neiser, R.A.; Gnäupel‐Herold, Thomas; Prask, H. J.; Sampath, Sanjay; Gouldstone, Andrew

doi:10.1016/j.actamat.2006.09.006

Cited by 141 publications

(54 citation statements)

References 18 publications

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“…These features appear to be common not only in cold spraying, but also in the closely-related process of warm spraying [105]. Another aspect of cold-sprayed microstructures is that they are highly anisotropic [106]. Properties of cold-sprayed deposits are to a large extent influenced by these features.…”

Section: Microstructurementioning

confidence: 98%

Cold spraying – A materials perspective

et al. 2016

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Cold spraying is a solid-state powder deposition process with several unique characteristics, allowing production of coatings or bulk components from a wide range of materials. The process has attracted much attention from academia and industry over the past two decades.The technical interest in cold spraying is twofold: first as a coating process for applications in surface technology, and second as a solid-state additive manufacturing process, offering an alternative to selective laser melting or electron beam melting methods. Moreover, cold spraying can be used to study materials behaviour under extremely high strain rates, high pressures and high cooling rates. The cold spraying process is thus considered to be relevant for various industrial applications, as well as for fundamental studies in materials science.This article aims to provide an overview of the cold spray process, the current understanding of the deposition mechanisms, and the related models and experiments, from a materials science perspective. IntroductionCold spraying (CS) is a solid-state material deposition technique, where micron-sized particles of a powder bond to a substrate as a result of high-velocity impact and the associated severe plastic deformation. Acceleration of particles to high velocities is obtained via expansion of a pressurised and (ironically) 'hot' gas through a diverging-converging nozzle.Despite heating the process gas -which is to provide higher acceleration of the gas and also to facilitate particle deformation through thermal softening -the feedstock remains in the solid state throughout the entire process; hence the name 'cold' spraying. This is to underline the contrast to conventional thermal spraying where particles are completely or partially molten upon impact onto the substrate. Alternative terminology includes cold gas spray, micro cold spray, cold gas dynamic spray, kinetic spray, supersonic particle deposition and metal powder application (MPA), all of which refer to the same principle of solid-state powder deposition as described above. CS is used for coating and repair. It is also used for additive manufacturing (AM) at relatively high deposition rates as compared to the methods based on selective laser or electron beam melting. The main advantage of CS is that it alleviates the problems associated with high temperature processing of materials, such as oxidation and unfavourable structural changes. It is possibly the only continuous method to produce bulk components of metastable materials that are available only in the powder form, e.g. as obtained from mechanical attrition or gas atomisation. The aim of the present paper is to provide an overview of CS from a materials perspective, particularly for a broader audience in materials research, e.g. with interest in dynamic phenomena, plasticity and phase transformations. In terms of application and properties, CS is perhaps best to be compared to thermal spraying processes, as in [24,25]. In view of relevant physical phenomena, however, CS is mos...

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Section: Microstructurementioning

confidence: 98%

Cold spraying – A materials perspective

et al. 2016

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“…These features complicate the interpretation of improved fatigue properties. Table 1 lists a summary [16,34,80,[106][107][108][109][110][111] of some processing-associated properties for the fabrication methods discussed in the previous section.…”

Section: Severe Plastic Deformation Processingmentioning

confidence: 99%

A Review of Fatigue Behavior in Nanocrystalline Metals

2009

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Nanocrystalline metals have been shown to exhibit unique mechanical behavior, including break-down in Hall-Petch behavior, suppression of dislocation-mediated plasticity, induction of grain boundary sliding, and induction of mechanical grain coarsening. Early research on the fatigue behavior of nanocrystalline metals shows evidence of improved fatigue resistance compared to traditional microcrystalline metals. In this review, experimental and modeling observations are used to evaluate aspects of cyclic plasticity, microstructural stability, crack initiation processes, and crack propagation processes. In cyclic plasticity studies to date, nanocrystalline metals have exhibited strongly rate-dependent cyclic hardening, suggesting the importance of diffusive deformation mechanisms such as grain-boundary sliding. The cyclic deformation processes have also been shown to cause substantial mechanicallyinduced grain coarsening reminiscent of coarsening observed during large-strain monotonic deformation of nanocrystalline metals. The crack-initiation process in nanocrystalline metals has been associated with both subsurface internal defects and surface extrusions, although it is unclear how these extrusions form when the grain size is below the scale necessary for persistent slip band formation. Finally, as expected, nanocrystalline metals have very little resistance to crack propagation due to limited plasticity and the lack of crack path tortuosity among other factors. Nevertheless, like bulk metallic glasses, nanocrystalline metals exhibit both ductile fatigue striations and metal-like Paris-law behavior. The review provides both a comprehensive critical survey of existing literature and a summary of key areas for further investigation.

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“…Thus, although CS coatings may be close to fully dense, they may not be fully bonded. This has been demonstrated in a number of investigations on mechanical, thermal, and electronic properties ( Ref 13,14). Although the specific contributions to, e.g., elastic modulus, thermal conductivity, and electrical conductivity have not been separated, qualitatively CS materials are known to behave as composites (e.g., Ref 14) of bulk material and interfaces.…”

Section: Introductionmentioning

confidence: 91%

Modified Indentation Techniques to Probe Inelasticity in Ni-5%Al Coatings from Different Processes

Choi

Sampath

et al. 2008

J Therm Spray Tech

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In this study, two types of indentation experiments were performed on metallic (Ni-5%Al) coatings prepared by cold spray, high velocity oxy-fuel and air plasma spray. In the first type, spherical tips were used with increasing loads, and subsurface deformation was observed using a modified bonded interface technique. In the second type, cyclic loading was imposed with a sharp tip, and tip displacement was continuously recorded. Results suggest that cold spray coatings are brittle under contact loads in their as-sprayed condition, and that they exhibit a size effect that is quite different from those of the other coatings. That is to say, heterogeneities in mechanical behavior exist not as much on the single particle level as expected, but on a much larger scale of order 100 microns. This is attributed to long unbonded regions between particles, in a coating of otherwise high density. Fracture mechanics arguments support this hypothesis.

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Integrated characterization of cold sprayed aluminum coatings

Cited by 141 publications

References 18 publications

Cold spraying – A materials perspective

Cold spraying – A materials perspective

A Review of Fatigue Behavior in Nanocrystalline Metals

Modified Indentation Techniques to Probe Inelasticity in Ni-5%Al Coatings from Different Processes

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