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One of the main specific features of the cold spray process is localisation during particle impact deformation. The resultant adiabatic shear instability is the phenomenon that is known to play a major role in the particle/substrate and particle/particle bonding and coating structure formation during the cold spray process. In this article, the cold spray process is numerically simulated as an impact between a single spherical particle with the substrate, and comparison with experimental results for Armco iron and stainless steel particles is made. To describe a deformation behavior of the two materials at high strain rates, the Johnson–Cook model has been chosen. The results indicate that the model accurately captures the grain distortion in the impact zone for both materials. This approach provides valuable information on the characterisation of the strain localisation at the particle/substrate interface. [ABSTRACT FROM PUBLISHER]

Abstract: The basic objective is the development of multifunctional multimaterial protective coatings using cold spraying (CS) and computer controlled detonation spraying (CCDS). As far as CS is concerned, the separate injection of each powder into different zones of the carrier gas stream is applied. Cu–Al, Cu–SiC, Al–Al2O3, Cu–Al2O3, Al–SiC, Al–Ti and Ti–SiC coatings are successfully sprayed. As to CCDS, powders are sprayed with a recently developed apparatus that is characterized by a high-precision gas supply system and a fine-dosed twin powder feeding system. Computer control provides a flexible programmed readjustment of the detonation gases energy impact on powder thus allowing selecting the optimal for each component spraying parameters to form composite and multilayered coatings. Several powders are sprayed to obtain composite coatings, specifically, among others, WC–Co–Cr+Al2O3, Cu+Al2O3, and Al2O3 +ZrO2. [ABSTRACT FROM AUTHOR]

In this paper the kinetics of multimaterial (composite) coating formation in case of cold spraying of metal powder mixtures is considered. In particular, a semi-empirical probability simulation model was developed and applied for prediction of coating final composition in dependence on initial percentage of metal powders in the blend. Developed model permits to take into account the differences between deposition efficiencies and granulometry of each spraying component. Experimental validation using there-component 316L-Cu-Tribaloy mixtures with different component percentage shows that simulation results are in a good agreement with experimental ones. It was demonstrated that the dependence of coating composition on percentage of mixture component is non-linear. The further work will be aimed on the enlarging of the current model to the cases with mixtures with significant difference between particle sizes of the components. [ABSTRACT FROM AUTHOR]

In current paper deposition of two- and three-component composite coatings on aluminium substrate using blends of stainless steel 316L, copper and Tribaloy T-700 powders is considered. Porosity value of obtained two-component copper-stainless steel coatings was significantly less than for with pure 316L coating (~ 1.5% vs. ~ 3.5%), but coating hardness was also smaller (230–250 HV 3 vs. ~ 280 HV 3 ). Deposited three-component coatings had the lowest porosity (~ 0.5%) and highest hardness value (~ 320 HV 3 ). Compositions of obtained coatings were not similar to ones of the initial blends. In particular, percentage of Tribaloy particles in the coating was approximately two times lower than in the mixtures, whereas the copper content in the coatings exceeds the percentage in initial blends due to significant difference between deposition efficiencies of the mixture components at tested spray parameters. Numerical simulation of particle impact parameters demonstrated that particle impact velocity of Tribaloy was significantly lower than the critical value that resulted in low deposition efficiency. [ABSTRACT FROM AUTHOR]

Abstract: Cold spray is a material deposition technique based on the high velocity particle–substrate impact. The last researches in this field show that efficiency of deposition depends not only on the particle impact velocity but also on the impact temperature. In order to control the particle impact temperature, a special powder preheater installed between the powder feeder and the nozzle could be applied. In the current paper, an influence of powder preheating on the particle impact parameters is numerically studied. Two cases with powder injection to subsonic and supersonic regions of the nozzle are considered. It is shown that artificially preheated 10–50μm copper particles axially injected to the supersonic region of the nozzle have higher impact temperature than the particles injected to the nozzle prechamber. This effect could be explained by the dependence of duration and intensity of gas–particle heat exchange on the location of powder injection point. It was also shown that in the case of powder injection to supersonic zone, the application of powder preheating could shift the particle impact parameters towards the deposition window without increasing the working gas stagnation temperature. [Copyright &y& Elsevier]

Abstract: Cold spray deposition of 1–3mm thick 316L coatings on aluminium substrate using nitrogen as a carrier gas is considered. Dependence of coating properties on particle size distribution and spraying strategy is studied. It was obtained that the absolute value of coating porosity depends on particle size distribution and could be varied from 3% (fine powders) to 8% (coarse powders). The pores are mostly concentrated along the boundaries between deposited layers and the shape of the boundaries is strongly influenced by spraying strategy. It was found that coating deposited using coarse powder has higher microhardness than the one deposited using fine powder, whereas adhesion does not depend on powder granulometry. Eventual decrease of coating porosity is analyzed. In particular, it is shown that laser post re-melting of the deposited coatings can decrease the porosity in the near-surface layers down to <1% with limited heat input to aluminium substrate. Evaluation of anodic polarization behavior showed that corrosion resistance of the laser-treated coating is close to the bulk material whereas performance of as-sprayed coatings is significantly lower. [Copyright &y& Elsevier]

Abstract: Cold Spray multicomponent coatings are deposited by a new powder injection method that consists of separate injection of each component of the powder mixture into a different zone of the carrier gas stream. Temperature and velocity of 10–40 µm-sized aluminium and copper particles at the nozzle outlet are calculated. It is shown that these values depend considerably on the location of the point where the powder was injected into the gas stream. The method is experimentally validated by producing a composite aluminium–copper coating. [Copyright &y& Elsevier]

Cold spraying is a coating deposition and additive manufacturing method capable of producing aluminum alloy parts at a high production rate under ambient conditions. In this work, the cold spray was applied for the deposition of AlMgScZr alloy initially developed for laser bed powder fusion additive manufacturing. The low-porosity deposits were successfully produced. Different heat-treatments as well as capsule-free hot isostatic pressing (HIP) were performed to homogenize the structure. TEM analysis of the deposits showed that heat-treatment at 300°С (3 h) + 360°С (4 h) allowed to release the Al 3 (Sc x ,Zr 1-x) hardening phase with mean grain size 7.6 nm. At the same time, the heat treatment had a limited influence on the material diffusion between the splats. Hot isostatic pressing conducted at 160 MPa and 300°С (3 h) + 360°С (4 h) was more efficient for enhancing of material diffusion between splats and also allowed to the material hardening by the release of Al 3 (Sc x ,Zr 1-x) hardening phase with the mean grain size 3.1 nm. The compressive strength tests revealed significant improvement of ultimate compressive strength and the strain at failure of the deposits after heat treatment and HIP. • Novel AlMgScZr alloy was successfully deposited by cold spray deposition. • Heat treatment of obtained AlMgScZr deposits was performed. • Ultrafine Al 3 (Sc x ,Zr 1-x) particles are homogeneously distributed in the Al matrix. [ABSTRACT FROM AUTHOR]

In this paper an effect of capsule-free hot isostatic pressing (HIP) on the porosity and mechanical properties of different cold spray deposits was experimentally evaluated. The HIP post-treatment significantly decreased (more than 2 times) the porosity of 316L and pure titanium deposits. The densification effect of HIP on the porous Ti6Al4V deposit was significantly less pronounced. Mechanical properties of the deposits after HIP were also improved. In particular, the tensile strength of the stainless steel, pure titanium and Ti6AL4V increased from 30 MPa, 70 MPa and 20 MPa to 211 MPa, 480 MPA and 560 MPa correspondingly. Compressive strength of the Al-Mg-Sc-Zr alloy samples after HIP was also increased ~25%. Improvement of mechanical properties is explained by material diffusion and microstructure changes during HIP cycle. • Hot isostatic pressing of different cold spray coatings was performed. • Porosity and properties of the samples before and after HIP were analyzed. • Significant improvement of the coatings density after HIP was found. • Tensile and compressive strength of the deposits were significantly increased by HIP. [ABSTRACT FROM AUTHOR]