Recent advances on bonding mechanism in cold spray process: A review of single-particle impact methods

Abstract

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

Design and Development of Stable Nanocrystalline High‐Entropy Alloy: Coupling Self‐Stabilization and Solute Grain Boundary Segregation Effects

“…In our recent work on NC-HEA, [42] we observed the selfsegregation of Cr and Fe by site competition in a model AlCoCrFe alloy, which stabilized the NC-HEA system even at high homologous temperature (773 and 873 K) without the introduction of a solute element, as in the case of thermodynamic approach for binary alloy systems; a phenomenon we termed as self-stabilization effect. Our work also shows that GB segregation competes with GB desegregation and phase decomposition, after which grain coarsening sets on.…”

“…[49] This criterion is considered to circumvent GB embrittlement upon solute segregation: high melting point elements increase bond strength, [61,62] and their segregation to the GBs improves GB cohesion (enriched GB) [60] We use a quaternary BCC AlCoCrFe HEA (detailed design and development procedure in Refs. [42,49]) as a solvent to validate the approach described in Figure 1b. As a starting point, we calculated the quaternary phase diagram of Al 25 Co 25 Cr 25 Fe 25 HEA using the CALculation of PHAse Diagrams (CALPHAD) approach via the Thermo-Calc 2023a software.…”

“…Some of the NC binary alloy systems include Fe─Zr, [31,32] Pd─Zr, [33] Ni─P, [34] Ru─Al, [35] Nb─Cu, [36] Ti─Cu [37] alloys, and those of Ni─W, Fe─Mg, and W─Ti alloy systems by Schuh and co-workers. [38][39][40] There are three categories of solute interactions established in binary alloy systems that can influence the stability of GBs, [41,42] namely co-segregation (because of the strong interaction between two elements, the element with weaker GB interaction segregates when the element with stronger GB interaction segregates), site competition (where two elements with GB segregation potential compete for GB sites because they are mutually repulsive; the element with the strongest GBs interaction eventually occupies these sites), and no interaction (where solute element addition has no significant effect on GB segregation).…”

Comparative Microstructural Study of Cold Sprayed Coatings Using Pure Aluminum and Aluminum Alloy Powders

“…Due to the impact of the aluminum particles, a high degree of plastic strain is accumulated in the deposited particles. Since it is not yet feasible to experimentally measure the plastic strain at the particle-substrate interface, we will use finite element models for the bonding mechanism of individual particles to understand the induced strain [19].…”

Computational Modeling of Cold Spray Process Using Particle-based Methods

“…The computational approach has the capability to provide an in-situ, short scale, and real-time understanding of the particle response which can be difficult to track by means of an experimental observation [7,8]. Basically, there are computational simulations at the scale of the powders up to the macroscopic scale of the deposit, using diverse methos such as Eulerian, Lagrangian, Coupled Eulerian Lagrangian (CEL), Arbitrary Lagrangian Eulerian (ALE) and SPH [9].…”