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Abstract: The purpose of this study is to provide an explanation of the effective parameters influencing thermal conductivity of copper deposited by particle impingement after subsequent annealing, with special emphasis on the contribution of electron and phonon conduction. As a result, after annealing, thermal conductivity and porosity of copper converge on a specific range of 288.5–320.5Wm−1 K−1 and 0.6–3.3%, respectively. Thermal conductivities of the coatings deposited by spherical powders are improved via annealing processes without a remarkable reduction of porosity. Furthermore annealing process increases the crystallite size and recovers the distorted lattice structures in (200), which hinders the passage of electrons and increases the compressive strain of parallel plane. The decrease of crystallite boundary areas via grain growth eliminates the interruption of the electron or phonon thermal conductivity directly from grain boundary scattering effect. [Copyright &y& Elsevier]

Abstract: When two copper splats are in contact, a resistance to heat transfer exists between the splats. In thermal spraying, the conductivity of the coating is mainly reduced by non-metallic bonds at internal interfaces and trapped oxides. In cold spraying, however, almost no oxidation occurs during spraying. To demonstrate the capabilities and advantages of Cold Spray for the manufacturing of a conductive copper coating, the present study is focused at comparing the different processing methods in the as-sprayed and the annealed state. As a result, the coatings sprayed with spherical copper particles showed superior thermal conductive characteristics than coatings sprayed with non-spherical particles. There was a critical annealing temperature giving the maximum thermal conductivity. Up to a critical temperature, the annealing process enhanced the thermal conduction between adjacent splats. But, over that temperature, the voids in the coating rearrange and concentrate along the grain boundaries. [Copyright &y& Elsevier]

Abstract: The smoothed particle hydrodynamics (SPH) method is applied to simulate the cold spray (CS) process by modeling the impact of a spherical powder particle on substrate.In this work, the adhesive interaction between the contacting surfaces is described by intersurface forces using the cohesive zone model. The application of the SPH method permits simulation of the impact process without the use of mesh and thus avoids the disadvantages of traditional numerical method in handling large deformations and tracing moving interfaces in the highly transient non-linear dynamic CS process. The simulated deformed particle shape evolution and estimated critical velocity from other sources were compared and good agreement was obtained. The analyses demonstrate the feasibility of the presented SPH methodology and the adhesive interaction model for simulating the deformation behavior of CS particles. [Copyright &y& Elsevier]

Abstract: Brittle SiC coatings have been successfully applied on Ni–Cr-based superalloy substrates to improve their oxidation resistance at high temperatures. The coating has been formed through the plastic deformation of the substrate with particle segmentation. The overlaid SiC layer shows the ability to slow down the outward chromium diffusion and hence sustaining the elemental content of the substrate. The formation of MoSi2 and SiO2 layers beneath SiC layer plays an important role in the oxidation rate reduction at elevated temperature environment. Scratch adhesion test result shows an excellent adhesion of SiC coating, as the coating delamination did not happen up to a 3.7N load. Four-point bending tests also pointed out the strong adhesion of oxide scales, which is necessary for further oxidation prevention. [Copyright &y& Elsevier]

• Discontinuous nozzle induces the flow to choke at the discontinuity location. • At the nozzle exit, the particle velocity reaches 190 m.s−1 for 60 μm diameter. • During cold-spray, polymeric particles are submitted to important thermal gradient. The manufacture of polymer coatings via the cold-spray process remains challenging owing to the viscoelastic-viscoplastic behavior exhibited by polymers. One crucial step to improve cold-spray polymer coating is to determine the particles' thermal history during their flight from inside the nozzle to their impact on the substrate. In this study, we propose estimating the velocity and temperature of an isolated polymer particle traveling through a nozzle with a sharp change in its cross-section. The preliminary results show that the geometric discontinuity constricts the flow, thereby increasing the particle velocity. Moreover, a significant thermal gradient is expected inside the particle, which in turn leads to a gradient of mechanical properties of the polymeric particle during impact. [ABSTRACT FROM AUTHOR]

Cold spray coatings elaboration requires optimization of numerous parameters in order to reach the best coatings' performances. A systematic approach can be avoided by using an experimental design. A Doehlert uniform shell design was applied in this work to Zn cold sprayed coating. Coatings were produced on steel substrates to provide high corrosion resistant layers. N 2 temperature and gas pressures varied from 200 °C to 320 °C and from 2.0 MPa to 3.0 MPa, respectively. Performance maps were plotted for two descriptors: (i) the interfacial porosity volume (substrate coating interface defects), (ii) coating thickness (i.e., coating durability), and validated with the polarization resistance (i.e., corrosion resistance). Results reported three set of optimized temperature and gas pressure values according to the descriptor. Two optimized protection modes can be obtained: a sacrificial mode from heterogeneities in the coating (290 °C and 3.0 MPa), and a barrier protection mode from homogeneous and dense coatings (320 °C and 2.5 MPa). Mechanism of corrosion has been investigated. • Zn-Cold sprayed coatings exhibit good alternative for corrosion protection. • Experimental designs are useful to optimise Cold sprayed coating. • Roughness of coatings contributes to the corrosion initiation [ABSTRACT FROM AUTHOR]