Deformation Behavior of Single Particle Cold Spray Ti-6Al-4V Splats

Abstract

The rapid development of cold spray technology has made it a viable option to repair and remanufacture damaged components as well as to create novel materials for biomedical applications. One of the most influential parameters of this distinctive process is the deposition velocity, which ultimately controls the degree of material deformation and material adhesion. Although the majority of materials can be successfully deposited at relative low deposition velocity (<700m/s), this is not representative of Ti alloys which have high yield strength. The amount of deformation and resultant properties of the coating are related to the velocity, temperature, and tensile strength of the particles. The ability to predict the deformation and resultant properties helps in developing process parameters and tailoring coatings to get the desired properties. In the current study, the particle deformation behavior and bonding with the substrate was investigated over a range of impact conditions. The effects of deposition velocity, gas temperature, gas pressure and nozzle stand-off distance were studied using cold sprayed splats of spherical Ti-6Al-4V powder deposited on to 316 SS substrate utilizing helium as a carrier gas. Finite element modeling of the impacted particles was conducted using Johnson-Cook high-strain-rate properties in a Lagrangian analysis to predict the overall deformation and estimated stress state of the impacted particles. Particle temperature due to impact was also predicted. Overall predictions were in good agreement with experimental results. Optical microscopy, scanning electron microscopy (SEM) and focused ion beam (FIB) were used to identify three distinct regions within the impact morphologies; these include the initial impact region, the jetting region, and the upper splat region.