Microstructural and mechanical properties of cold sprayed coatings with an emphasis on Ti-6Al-4V

In some applications, cold spray could be used to manufacture titanium alloys as well as nickel based superalloys: this process reduces production times and limits deleterious effects like oxidation, thanks to its solid state deposition. However, the high resistance of these alloys implies that really high velocity deposition is needed to achieve dense deposition, which could lessen the mechanical properties of the material.

In this study, these alloys are examined in terms of mechanical and microstructural properties to know their potential as sprayed materials. Firstly, a parametric study was carried out in order to reduce porosity in deposits. Then, microstructural and mechanical analyses were achieved in order to detect material modifications after deposition. Mechanical test results were clarified by correlation with microstructure and porosity analyses, allowing us to compare cold sprayed with forged samples.

Finally, regarding the structural integrity of a material, residual stresses play a critical role. They were studied to provide a better understanding of cold spray deposition: with Ti-6Al-4V, the prevailing stresses during deposition are in tension. These tensile stresses being detrimental for the material fatigue resistance, a better understanding of this phenomenon along with an attempt to reduce them are thus crucial.