In this study, a downstream injection cold spray nozzle is modeled numerically under various loadings. Instead of micron-sized particles, liquid feedstock as a carrier of nanoparticle suspension is fed into the nozzle through a port located 6 mm downstream of the nozzle throat at the diverging section. Water is used as the liquid carrier with a droplet size distribution of 5-100 µm and liquid-to-gas ratio ranging from 5 to 15%. The radial injection of droplets is simulated by Lagrangian particle tracking which includes the effects of heating and evaporation. The effect of the feedstock on downstream flow is analyzed and the optimum solid-to-liquid fraction in the suspension is determined.

Surface treatment has become an effective method to improve corrosion resistance of magnesium alloys which are the lightest commercial structural alloys with superior specific strength and stiffness. Low pressure cold spraying is used to locally deposit aluminium on AZ31 in order to enhance general and galvanic corrosion of magnesium. This study is aimed at numerical estimation of the residual stress profile due to cold spray coating using FEM. The impact of particles on the substrate is modelled in Abaqus Explicit. The challenge of AZ31 simulations is the intrinsic yield asymmetry and anisotropy which results different behaviour of the material along different direction both in tension and compression. On the other hand, there is no precise material model capable of considering the yield asymmetry and anisotropy experienced by AZ31 in Abaqus. This paper studies the effect of anisotropy of the AZ31 on residual stress induced by cold spray. The results are compared with experimental X-Ray diffraction measurements. It is suggested that an isotropic analysis in the dominant stress direction of AZ31 may result in good estimation of the residual stress profile.

In this study, low-pressure cold spraying was used to deposit Al and Al-Al 2 O 3 composite powders on different substrate materials, including steel, aluminum, and magnesium alloy. Corrosion performance was evaluated by electrochemical testing in 1M NaCl electrolyte and microstructure was examined by means of SEM analysis. The results show that the corrosion potential of Al-Al 2 O 3 coatings depends on the content of alumina and that its presence does not appear to accelerate dissolution and failure of passivation oxide films. The investigation also revealed that pure aluminum coatings on aluminum alloy substrates can act as sacrificial anodes, thus providing corrosion protection.

This paper describes the influence of post-spray heat treatment parameters on mechanical properties of Ni-TiC composite coatings. Thin Ni-TiC composite coatings were produced by low pressure cold gas dynamic process (also referred as cold spray or kinetic spray process) on an Inconel alloy substrate. In the coating process, mechanically mixed micron-sized Ni-TiC powders (~50 µm) were injected into a de-Laval nozzle propelled by a supersonic gas stream to high velocity (>300 m/s) to impinge upon a substrate. The coatings are formed subsequently as the metallic particles are severely deformed plastically and bonded to both the substrate and to one another. However the tensile adhesion strength levels were determined to be in the range of 10-14 MPa. A subsequent post-spray heat treatment in vacuum was found to enhance the bond strength of the coated particles with the substrate due to good metallurgical bonding caused by diffusion mechanism.

A new approach is explored to achieve the aluminum alloy powder layer from nanoparticle contained metallic powder mixture feedstock by Low Pressure Gas Dynamic Spray (LPGDS) or Cold Spray (LPCS). In this approach, mixtures of micron-sized aluminum powder (average size of 10 µm) and alloying nano-powder of Cu, Si and TiC (200-500 nm), at appropriate proportions to compositions of Al-5wt%Cu, Al-5wt%Cu-0.75wt%Si and Al- 5wt%Cu-5wt%TiC with polymer binder were prepared by stirring. Then, the powder mixture was compacted into pellets, dryed, and further milled to obtain the particle agglomerates (average size of 50 µm) . The powder feedstock were sprayed by LPCS. In this paper, we investigate the spraying behavior Al-based nanoparticle contained powder mixtures the microstructural development and mechanical properties of deposited layers using a microindentation, scanning probe microscopy, scanning electron microscopy and energy dispersive X-ray analysis.

The corrosion behavior of Al alloys, produced by cast and powder (Low Pressure Gas Dynamic Spray or Cold Spray) technologies, was examined in 3% sodium chloride solution from the viewpoint of localized corrosion. The susceptibility to localized corrosion is known to be strongly affected by intermetallic phases present in the alloy’s microstructure. The influence of individual cathodic and anodic intermetallic phases was investigated by using a microelectrochemical setup and by electrochemical methods. The optical and scanning electron microscopy data reveal that the cast and powdered alloys experience localized corrosion due to presence of the intermetallic phases which results in the micro-corrosion effects such as exfoliation corrosion, intergranular or crevice corrosion, and most severely pitting. Cast material has lower corrosion properties because of the higher heterogeneity of the structure as compared with powder sprayed composite.

The proposed work describes recent efforts to develop metastable Al-Fe-V-Si coatings for internal-combustion engine applications with higher mechanical properties at high operating temperatures. To do so, the metastable solid powder alloy was engineered from rapid solidification technique (namely gas atomization). The metastable alloy powder was deposited using the Cold Spray process in order to produce protective coatings on top of existing parts. The critical velocity, above which Cold Spray deposition takes place, was successfully achieved and Al-Fe-V-Si coatings were produced. The microstructure of the feedstock powder was retained in the coatings produced, showing the potential of the Cold Spray process to produce metastable coatings for internal combustion engine applications.

The present study was carried out to evaluate the applicability of the Gas Dynamic Spraying (GDS) of different powder compositions for depositing wear-resistant composite coatings on iron and steel castings. This process, simply known as “cold spray,” utilizes the kinetic energy of particles sprayed at supersonic velocities to produce a bonding of the particles to the substrate. Ni and Cu based coatings containing W, Zn and TiC as reinforcement were made by the low pressure GDS technique and investigated. The coatings microstructures were studied by both optical and scanning electron microscopy. Phase composition, hardness and wear resistance of the GDS coatings were analyzed. The ball-on-disc sliding wear test was used for assessing the wear resistance characteristics of the coatings using a ceramic (Si 3 N 4 ) ball. W and TiC reinforced coatings showed the best wear performance. These were further evaluated in greater detail. In addition to the obtained test results, the application prospects for such GDS coatings were discussed.

A computational fluid dynamic (CFD) model of the cold gas dynamic spray process is presented. The gas dynamic flow field and particle trajectories within an oval shaped supersonic nozzle as well as in the immediate surroundings of the nozzle exit, before and after the impact with the target plane, are simulated. Predicted nozzle wall pressure values compare well with experiment. In addition, predicted particle velocity results at the nozzle exit are in qualitative agreement with those obtained using a side-scatter laser Doppler anemometer (LDA.) Details of the pattern of particle release into the surroundings are visualized in a convenient manner.