Fracture Toughness of Cold Sprayed Pure Metals

Kovářík, Ondřej; Siegl, J.; Čížek, Jan; Chráska, Tomáš; Kondás, Ján

doi:10.1007/s11666-019-00956-z

Cited by 26 publications

(17 citation statements)

References 30 publications

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“…The modulus of copper is 110 GPa, but the other parameters in this expression are not known exactly. The fracture toughness can be bounded between that for perfectly brittle fracture (K IC ∼1 MPa m 1/2 ) and that for ideally coherent bulk copper (K IC ∼60 MPa m 1/2 ) [37]. However, these bounds are too far apart to be practically useful and intuitively do not correspond to the expected physical situation of evaluating a transient metallic bond interface in copper.…”

Section: Jetting-associated Energy Dissipation Mechanismsmentioning

confidence: 96%

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The Transition From Rebound to Bonding in High-Velocity Metallic Microparticle Impacts: Jetting-Associated Power-Law Divergence

Sun

Veysset

Nelson

et al. 2020

Journal of Applied Mechanics

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A metallic microparticle impacting a metallic substrate with sufficiently high velocity will adhere, assisted by the emergence of jetting—the splash-like extrusion of solid matter at the periphery of the impact. In this work, we compare real-time observations of high-velocity single-microparticle impacts to an elastic–plastic model to develop a more thorough understanding of the transition between the regimes of rebound and bonding. We first extract an effective dynamic yield strength for copper from prior experiments impacting alumina spheres onto copper substrates. We then use this dynamic yield strength to analyze impacts of copper particles on copper substrates. We find that up to moderate impact velocities, impacts and rebound velocities follow a power-law behavior well-predicted on the basis of elastic-perfectly plastic analysis and can be captured well with a single value for the dynamic strength that subsumes many details not explicitly modeled (rate and hardening effects and adiabatic heating). However, the rebound behavior diverges from the power-law at higher impact velocities approaching bonding, where jetting sets on. This divergence is associated with additional lost kinetic energy, which goes into the ejection of the material associated with jetting and into breaking incipient bonds between the particle and substrate. These results further support and develop the idea that jetting facilitates bonding where a critical amount of bond formation is required to effect permanent particle deposition and prevent the particle from rebounding.

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Section: Jetting-associated Energy Dissipation Mechanismsmentioning

confidence: 96%

“…A better approximation can be made by directly using the bulk fracture toughness of unannealed cold-sprayed copper deposits, which are on the order of ∼9 MPa m 1/2 [37] and which better reflect the nature of the bonded regions in the present experiments. With this value, Eq.…”

Section: Jetting-associated Energy Dissipation Mechanismsmentioning

confidence: 99%

The Transition From Rebound to Bonding in High-Velocity Metallic Microparticle Impacts: Jetting-Associated Power-Law Divergence

Sun

Veysset

Nelson

et al. 2020

Journal of Applied Mechanics

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“…The dynamic elastic modulus was measured using an unnotched specimen vibrating at a surface stress amplitude increasing from 10 MPa up to 100 MPa and then decreasing back again. The corresponding deformation was obtained using a full fit of the displacement field obtained by DIC as described in [9]. The crack growth rate test was performed in resonance with the stress ratio R ~ -1.…”

Section: Methodsmentioning

confidence: 99%

Mechanical and Fatigue Properties of Tungsten Heavy Alloy Prepared by RF-Plasma

Kovářík

Čech

Klečka

et al. 2021

Thermal Spray 2021: Proceedings From the International Thermal Spray Conference

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Tungsten heavy alloy (WHA) of W-Ni composition was deposited from a blend of standard thermal spray powders using radio frequency inductively coupled plasma torch (RF-ICP) in a protective atmosphere. The deposit (RF WHA) contained a fully developed WHA structure; i.e.; spherical W particles embedded in a Ni-rich matrix. The bending tensile strength Rm; bending yield strength Rp;0.2; and elastic modulus of the deposit were compared with two W-Ni-Co references fabricated by powder metallurgy (PM WHA) via sintered and quenched (PMSQ); and forged and annealed (PM-FA). While the RF deposit properties are comparable with the PM-SQ reference; the PMFA exhibited higher mechanical properties. The deposit showed very limited ductility A < 3%. The fatigue crack growth rate in the deposit measured in bending (R < -1) was comparable to the PM-SQ reference material in the near-threshold region whereas the forged PM-FA had significantly better fatigue performance. In the near-threshold fatigue regime; the crack growth took place in the Ni-rich matrix. In the Paris regime; the similar fracture mode was observed; with the exception of PM-SQ; where the tungsten particles fracture contributed significantly. The static failure was exclusively trans-particle in RF WHA; while both PM WHAs failed by a mix of ductile matrix failure and trans-particle cleavage fracture. The fracture toughness of the deposit was significantly lower than the references. These early results indicate that RF-plasma spray is a suitable and efficient manufacturing method for production of WHA materials; however with limited mechanical properties in some aspects.

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“…The stress-strain properties in both tension and compression were obtained from bending tests following the method of Herbert [7] and the setup described in [8]. The method uses four-point bending fixture with an outer span L = 27 mm and an inner span l = L/2.…”

Section: Methodsmentioning

confidence: 99%

“…The fracture toughness measurement on fatigue pre-cracked specimens followed the ASTM E1820 standard. The precracking was performed at crack growth rate of da/dN ~ 10 -9 m. The crack length and crack opening displacement (COD) was evaluated from the displacement field obtained by digital image correlation (DIC) by a method described in [8]. The DIC approach further simplifies the COD measurement and makes it more robust compared to videoextensometer-based measurement used e.g.…”

Section: Figure 1 Schematic Drawing Of Specimen Orientationmentioning

confidence: 99%

Mechanical and Fatigue Properties of Diamond Reinforced Cu and Al Metal Matrix Composites Prepared by Cold Spray

Kovářík

Yin

Lupoi

et al. 2021

Thermal Spray 2021: Proceedings From the International Thermal Spray Conference

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Diamond-reinforced composites prepared by cold spray are emerging materials simultaneously featuring outstanding thermal conductivity and wear resistance. Their mechanical and fatigue properties relevant to perspective engineering applications were investigated using miniature bending specimens. Cold sprayed specimens with two different mass concentrations of diamond 20% and 50% in two metallic matrices (Al – lighter than diamond; Cu – heavier than diamond) were compared with the respective pure metal deposits. These pure metal coatings showed rather limited ductility. The diamond addition slightly improved ductility and fracture toughness of the Cu-based composites; having a small effect also on the fatigue crack growth resistance. In case of the Al composites; the ductility as well as fatigue crack growth resistance and fracture toughness have improved significantly. The static and fatigue failure mechanisms were fractographically analyzed and related to the microstructure of the coatings; observing that particle decohesion is the primary failure mechanism for both static and fatigue fracture.

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Fracture Toughness of Cold Sprayed Pure Metals

Cited by 26 publications

References 30 publications

The Transition From Rebound to Bonding in High-Velocity Metallic Microparticle Impacts: Jetting-Associated Power-Law Divergence

The Transition From Rebound to Bonding in High-Velocity Metallic Microparticle Impacts: Jetting-Associated Power-Law Divergence

Mechanical and Fatigue Properties of Tungsten Heavy Alloy Prepared by RF-Plasma

Mechanical and Fatigue Properties of Diamond Reinforced Cu and Al Metal Matrix Composites Prepared by Cold Spray

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