In this work, fully dense titanium parts are fabricated by cold gas dynamic spraying (CGDS). Titanium powder is deposited using a low-pressure CGDS process with nitrogen as the carrier gas. The density, porosity, hardness, and tensile properties of the parts produced are determined and discussed.

This work investigates the biofunctionality and corrosion resistance of titanium (Ti) and Ti/bioglass composite coatings. Commercially pure Ti (CP-Ti) and 45S5 bioglass powders were deposited on CP-Ti plates by air plasma spraying and the coating samples were placed in Hanks’ balanced salt solution for simulated body fluid (SBF) testing. After four weeks of immersion, the coatings were examined by SEM imaging and EDS and XRD analysis. EDS analysis showed that the Ca content on the Ti/bioglass coatings increased from 4 to 16 wt%, while no increase in Ca was observed on the Ti coatings. Hydroxyapatite formation was found on both coatings, although the relative intensity of HA on the XRD spectrum was higher for the Ti/bioglass composite layers. Weight measurements before and after immersion showed that the CP-Ti samples experienced a mass gain and that the Ti/bioglass samples underwent a mass loss likely due to the dissolution of calcium and phosphate.

In this paper, it is shown that mixing metal powders can lead to improvements in cold sprayability (i.e. increases in the deposition efficiency and decreases in the porosity) of the ‘matrix’ powder. This finding is illustrated with the following ‘binary’ mixtures: Ti – 6Al-4 V and commercial purity Ti; stainless steel and iron; spherical tantalum with irregular tantalum and two types of spherical tantalum with different characteristics. It is shown that a critical addition can significantly influence cold sprayability, but above this, there is little change in cold sprayability. Hardness differences are considered to be the first order influence, but differences in particle sizes and morphology may also be contributing factors.

Cold spraying is particularly suitable for elaborating heat and oxidation sensitive coatings. Due to the fact that the particles are not melted during the spraying process, it is thus possible to elaborate coatings without chemical modifications. Nevertheless, according to the materials considered, some interface defects can be detected inducing an inadequate adhesion between the substrate and the coating. Bonding mechanisms are not only strongly dependent on the particle velocity but also on the state of the surfaces. By this way, surface pre-treatments can be necessary to improve adhesion. From all the surface modification technologies, laser ablation process is very interesting due to its flexibility by using optical fibers and due to the perfect control over the treated area. It is then possible to interact with the material during all the spraying process on the substrate surface as well as on the interface layers. This is particularly the aim of this study which consists in exploring the laser influence, implementing the PROTAL process, on the different interfaces quality for coatings elaborated by cold spray on metallic substrates. By controlling the chemical composition of the materials, the coating cohesion as well as the adhesion level, coatings were sprayed on pure titanium and titanium and nickel based alloy substrates.

During cold spraying, small particles are propelled to supersonic speeds and adhere to the substrate on impact, forming a strong bond. This work examines the effect of process gas temperature on cold spray coatings produced from commercially pure (CP) titanium powders. Nitrogen gases at 400, 600, and 800 °C were used as the propellant and nitrogen and oxygen content in the titanium coating was examined. The findings suggest that at high gas temperatures, the oxygen and nitrogen in the commercially pure titanium deposits increases at the particle boundaries.

Cold gas dynamic spraying has shown to be a promising approach for fabricating titanium structures directly from powder in the absence of a controlled atmosphere. This study investigates the effect of annealing on the microstructure, hardness, and tensile properties of commercial purity titanium deposited under cold spray conditions. Equiaxed grains with ultrafine grain structure are observed in the annealed samples. A physical based model is proposed for recrystallization of cold-sprayed titanium deposits and the results are compared with conventional cold-rolled and annealed titanium products.

In this study, three kinds of engineering metals, which are aluminum (1100-H12), commercially pure titanium and mild steel were combined as particle/substrate and classified into four cases, i.e., soft/soft, hard/hard, hard/soft and soft/hard, according to their physical and mechanical properties respectively. Based on finite element modeling, impacting interface elements of four cases were analyzed and impact behaviors were numerically characterized. For soft/soft and hard/hard cases, the maximum temperature at the substrate side, which approached melting point, is higher than that of particle side when the shear instabilities occur. In particular, the different size of thermal boost-up zone was numerically estimated and theoretically discussed for these two cases. Meanwhile, for soft/hard and hard/soft cases, the specific aspect of shear instability, which has very high heat-up rate, was always observed at the relatively soft impact counterpart, and a thin molten layer was expected as well. Thus, the successful bonding of the above mentioned four cases can be predicted as a result of the synergistic effect of localized shear instability with interfacial melting.