Solid-state cold spraying of Ti and its alloys: A literature review

Cold Gas Dynamic Spray or Supersonic Cold Spray, or simply ‘Cold Spray’, is an emerging technology for rapidly building thin films, thick coatings and large-scale additive manufacturing at relatively low temperatures. In a cold spray process, particles are accelerated to supersonic speeds by a propellant gas and impact a substrate, thus producing a strong bonding with the substrate and subsequently forming a deposit via layer-by-layer buildup. The scalability and low cost of this method make it promising for many applications in industry, such as metal component surface repair/enhancement/restoration and functional coatings for electrical, thermal, biomedical, energy storage, and nuclear plant applications. However, cold sprayed deposits usually require post process treatments to further modify their microstructures and mechanical properties in order to obtain the desired performances. A number of studies have been carried out on this topic. Here, recent progress in different post process treatments on cold sprayed deposits is reviewed, including heat treatment, friction-stir processing, shot peening, and laser re-melting. The effects of these post treatments on the microstructure, residual stress and mechanical properties of cold sprayed deposits are discussed.

Post-process treatments on supersonic cold sprayed coatings : a review

Surface condition, especially surface roughness of substrates, critically influences the adhesion of cold-sprayed titanium alloy coatings. To study this, Ti6Al4V (Ti64) coatings were deposited on Ti64 substrates with increasing surface roughness (Ra) from 0.05 µm (polished surface) to 5.4 µm (water-jet cut surface). It was found that the substrate surface roughness did not significantly affect the porosity, hardness and coating surface roughness because these properties were dependent on the deposition parameters such as propellant gas pressure and temperature and nozzle traverse speed. The adhesion test results showed that smoother substrate surfaces improved the coating bond strength of the cold-sprayed Ti64 coatings from about 7.1 MPa (Ra: 5.4 µm, interface failure) to 68.7 MPa (Ra: 0.05 µm, glue failure). The fracture characteristics of the debonded coating/substrate interfaces revealed that there were more adiabatic shear-induced craters observed on the smoother substrate surfaces. Finite element modeling also showed that the substrate surface features (i.e., peaks and valleys) possibly prevented the intimate contact between the particles and substrate and thus induced the non-uniform distributions of temperature, stress and strain at the particle/substrate interface.

Effect of Substrate Surface Roughness on Microstructure and Mechanical Properties of Cold-Sprayed Ti6Al4V Coatings on Ti6Al4V Substrates

ABSTRACT Cold spray is an emerging surface coating technology for rapidly developing thick coating, thin films and additive manufacturing of parts at relatively low temperatures. The low cost and scalability of a cold spray method make it promising for diverse industrial applications. Presently, the cold spray coating is widely used for the production of machine parts, materials and tools that requires the desired surface properties. However, the consideration of process parameters setting develops a reliable coating having high mechanical, tribological, fatigue and morphological properties for demanding coating applications. Hence, the aim of this paper is to study the effect of processing conditions (pressure and temperature of propellant gas, powder particle morphology and post-process treatments) on the tribological and mechanical properties of cold-sprayed coatings. Further, the effect of microstructure and processing conditions on the fatigue and static characteristics of cold spray material is also discussed.

Influence of processing conditions on the mechanical, tribological and fatigue performance of cold spray coating: a review

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Tribology and Mechanics of Magnetic Storage Devices

The surfaces of cold-sprayed Ti-6Al-4V (Ti64) coatings were laser irradiated with different laser powers of 50–200 W to study the effects of Nd:YAG laser surface treatment on their tribological pro...

/pdf/effects-of-nd-yag-laser-surface-treatment-on-tribological-4comciitr7.pdf

Effects of Nd:YAG Laser Surface Treatment on Tribological Properties of Cold-Sprayed Ti-6Al-4V Coatings Tested against 100Cr6 Steel under Dry Condition

Adrian Wei Yi Tan

Papers

Effects of Nd:YAG Laser Surface Treatment on Tribological Properties of Cold-Sprayed Ti-6Al-4V Coatings Tested against 100Cr6 Steel under Dry Condition