“…A notable observation from this work [50] is the evidence of bare metal extrusion into the gaps between trapped delaminated oxides or oxide islands that are either still attached to the particle (c, d) the coefficient of restitution, ratio of the rebound and impact velocity, as a function of the v i for 14 micronsized aluminium (AA 1000) and aluminium alloy (AA 2024) particles, reprinted with permission from Ref. [52], copyright 2019 Elsevier; and (e) SEM micrographs of etched undeformed AA 2024 alloy that shows second-phase particle distribution.…”
Section: Oxide Layer Breakup and Delaminationmentioning
confidence: 54%
“…In a recent single microparticle impact study by Lienhard et al [ 112 ], the effect of oxide thickness on was experimentally quantified: with just ~ 60% increase in oxide thickness from 5 nm in the as-received state, of aluminium microparticles increased by more than 100 m/s. Recent works also show the presence of amorphous carbon on Cu particle surface [ 50 , 114 ]; it is believed that carbon possibly originated from contamination during particle production, handling, and storage, and it provides additional barriers to metallurgical bonding [ 114 ]. Figure 5 Schematic diagrams showing common (a) extrinsic and (b) intrinsic barriers to bonding during cold spray process.…”
Section: New Insights On Bonding In Cold Spray Processmentioning
confidence: 99%
“… Figure 6 (a) Cross-sectional SEM/STEM micrographs and EDS maps of undeformed Cu particles showing surface oxide, pores, and nano-sized dispersoids (orange arrows), Adapted with permission from Ref. [ 50 ], copyright 2021 Elsevier; (b) the ADF STEM images and EELS maps of a Cu particle/substrate interface showing the presence of surface oxides, spherical nano-dispersoids, and Carbon, reprinted with permission from Ref. [ 114 ], copyright 2022 Elsevier; (c, d) the coefficient of restitution, ratio of the rebound and impact velocity, as a function of the for 14 micron-sized aluminium (AA 1000) and aluminium alloy (AA 2024) particles, reprinted with permission from Ref.…”
Section: New Insights On Bonding In Cold Spray Processmentioning
confidence: 99%
“…At an impact velocity below the , the particle rebounds [ 25 ]. There are quite a few mechanisms of bonding proposed in the literature [ 29 , 50 ] some of which are under debate. Some of these debates include whether or not adiabatic shear instability is required for bonding [ 51 , 52 ], the roles of jetting—outward ejection of material from the particle–substrate interface, native surface oxide layer [ 29 , 53 ], interfacial melting [ 54 – 56 ], and interface solid-state amorphization [ 57 , 58 ]; these mechanisms will be examined in details in the latter section.…”
Section: Introduction and Overviewmentioning
confidence: 99%
“…Summarized previous works on single impact and their conclusions on contributions to bonding.Jet formation and subsequent material fragmentation are directly linked to bonding Al/Al[112] Oxide layer composition, crystallinity, and thickness have significant influence on bonding Cu/Cu[114] Amorphous carbon and spherical copper oxides are additional barriers to bonding, in addition to the well-known surface native oxides Cu/Cu[50] Oxide layer delamination, in addition to oxide breakup contributes to clean metal-metal contact development. Jetting enhances the delamination process Ballistic airgun Pb/Pb[103] Bonding is promoted where jetting and melting occurred at regions of maximum equivalent plastic strain and temperature Wipe test Ti/AlMg 3[23] Bonding is dominantly caused by shear instabilities under plastic deformation and to a less extent by the heat of friction Cu/Al[101] Mechanical adhesion is improved when both particle and substrate jet.…”
Cold spray (CS) processing is a layer-by-layer solid-state deposition process in which particles at a temperature below their melting point are launched to sufficiently high velocities to adhere to a substrate (and previously deposited particles), forming coatings/parts. Despite being in existence for over four decades, particle bonding mechanisms in the CS process are unclear due to the complex particle–particle/carrier gas interactions that obscure assessment. This review evaluates recent findings from single-particle impact approaches that circumvent these complexities and further provide new insights on bonding mechanisms. Theories on the evolution of oxide layer breakup and delamination, adiabatic shear instability, jetting, melting, and interface solid-state amorphization that contributes to bonding are assessed and carefully reviewed. Although there is a unified condition in which bonding sets on, this study shows that no singular theory explains bonding mechanism. Rather, dominant mechanism is a function of the prevailing barriers unique to each impact scenario.
Graphical abstract
“…A notable observation from this work [50] is the evidence of bare metal extrusion into the gaps between trapped delaminated oxides or oxide islands that are either still attached to the particle (c, d) the coefficient of restitution, ratio of the rebound and impact velocity, as a function of the v i for 14 micronsized aluminium (AA 1000) and aluminium alloy (AA 2024) particles, reprinted with permission from Ref. [52], copyright 2019 Elsevier; and (e) SEM micrographs of etched undeformed AA 2024 alloy that shows second-phase particle distribution.…”
Section: Oxide Layer Breakup and Delaminationmentioning
confidence: 54%
“…In a recent single microparticle impact study by Lienhard et al [ 112 ], the effect of oxide thickness on was experimentally quantified: with just ~ 60% increase in oxide thickness from 5 nm in the as-received state, of aluminium microparticles increased by more than 100 m/s. Recent works also show the presence of amorphous carbon on Cu particle surface [ 50 , 114 ]; it is believed that carbon possibly originated from contamination during particle production, handling, and storage, and it provides additional barriers to metallurgical bonding [ 114 ]. Figure 5 Schematic diagrams showing common (a) extrinsic and (b) intrinsic barriers to bonding during cold spray process.…”
Section: New Insights On Bonding In Cold Spray Processmentioning
confidence: 99%
“… Figure 6 (a) Cross-sectional SEM/STEM micrographs and EDS maps of undeformed Cu particles showing surface oxide, pores, and nano-sized dispersoids (orange arrows), Adapted with permission from Ref. [ 50 ], copyright 2021 Elsevier; (b) the ADF STEM images and EELS maps of a Cu particle/substrate interface showing the presence of surface oxides, spherical nano-dispersoids, and Carbon, reprinted with permission from Ref. [ 114 ], copyright 2022 Elsevier; (c, d) the coefficient of restitution, ratio of the rebound and impact velocity, as a function of the for 14 micron-sized aluminium (AA 1000) and aluminium alloy (AA 2024) particles, reprinted with permission from Ref.…”
Section: New Insights On Bonding In Cold Spray Processmentioning
confidence: 99%
“…At an impact velocity below the , the particle rebounds [ 25 ]. There are quite a few mechanisms of bonding proposed in the literature [ 29 , 50 ] some of which are under debate. Some of these debates include whether or not adiabatic shear instability is required for bonding [ 51 , 52 ], the roles of jetting—outward ejection of material from the particle–substrate interface, native surface oxide layer [ 29 , 53 ], interfacial melting [ 54 – 56 ], and interface solid-state amorphization [ 57 , 58 ]; these mechanisms will be examined in details in the latter section.…”
Section: Introduction and Overviewmentioning
confidence: 99%
“…Summarized previous works on single impact and their conclusions on contributions to bonding.Jet formation and subsequent material fragmentation are directly linked to bonding Al/Al[112] Oxide layer composition, crystallinity, and thickness have significant influence on bonding Cu/Cu[114] Amorphous carbon and spherical copper oxides are additional barriers to bonding, in addition to the well-known surface native oxides Cu/Cu[50] Oxide layer delamination, in addition to oxide breakup contributes to clean metal-metal contact development. Jetting enhances the delamination process Ballistic airgun Pb/Pb[103] Bonding is promoted where jetting and melting occurred at regions of maximum equivalent plastic strain and temperature Wipe test Ti/AlMg 3[23] Bonding is dominantly caused by shear instabilities under plastic deformation and to a less extent by the heat of friction Cu/Al[101] Mechanical adhesion is improved when both particle and substrate jet.…”
Cold spray (CS) processing is a layer-by-layer solid-state deposition process in which particles at a temperature below their melting point are launched to sufficiently high velocities to adhere to a substrate (and previously deposited particles), forming coatings/parts. Despite being in existence for over four decades, particle bonding mechanisms in the CS process are unclear due to the complex particle–particle/carrier gas interactions that obscure assessment. This review evaluates recent findings from single-particle impact approaches that circumvent these complexities and further provide new insights on bonding mechanisms. Theories on the evolution of oxide layer breakup and delamination, adiabatic shear instability, jetting, melting, and interface solid-state amorphization that contributes to bonding are assessed and carefully reviewed. Although there is a unified condition in which bonding sets on, this study shows that no singular theory explains bonding mechanism. Rather, dominant mechanism is a function of the prevailing barriers unique to each impact scenario.
Graphical abstract
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