Particle In-Flight Velocity and Dispersion Measurements at Increasing Particle Feed Rates in Cold Spray

Abstract

Cold Spray (CS) is attracting the interest of research and industry due to its rapid, solid-state particle deposition process and the respective advantages over conventional deposition technologies. The acceleration of the particles is critical to the efficiency of CS, and previous fluid dynamic investigations rarely consider the particle feed rate important. However, because higher particle loadings are typically used in the process, the effect of this cannot be assumed negligible. This study therefore investigates the particle velocities in the supersonic jet of an advanced CS system at low and high pressure levels and varying particle feed rates using Particle Image Velocimetry (PIV). The particle dispersion and velocity evolution along the jet axis were investigated for several feedstock materials. It was found that the average particle velocity noticeably decreases with increasing particulate loading in all cases. This effect is aggravated for lower working pressures, but mainly depends on the feedstock material, which implies more complex, volume-fraction related physics playing a role in this respect. Moreover, the velocity distribution and particle dispersion were also observed to be influenced by the feed rate, depending on the particle material. Increased particle feed rates hence affect the magnitude and distribution of impact velocity and consequently the efficiency of CS. In particular, numerical models neglecting this interconnection are required to be further improved, based on these experimental studies.

Cold-Sprayed Al6061 Coatings: Online Spray Monitoring and Influence of Process Parameters on Coating Properties

“…The particle velocities as a function of pressure and temperature are presented in Figure 4. When pressure and temperature increase, particle velocity increases as stated in many studies [12,13,25,26,32]. In the present study, temperature has a higher influence on particle Figure 3.…”

“…Particle velocities sprayed with the highest parameters were 10.5% higher than sprayed with the lowest parameters. Meyer et al [25] have measured particle velocities for Al with the PIV technique and the velocity dependence on the particle mass feed rates, resulting in decreased particle velocities with higher feed rates. Aluminum particles sprayed with the pressure of 15 bar or 30 bar had average particle velocities of ~450 and ~540 m/s, respectively [25], using similar feed rates as we have used.…”

“…Meyer et al [25] have measured particle velocities for Al with the PIV technique and the velocity dependence on the particle mass feed rates, resulting in decreased particle velocities with higher feed rates. Aluminum particles sprayed with the pressure of 15 bar or 30 bar had average particle velocities of ~450 and ~540 m/s, respectively [25], using similar feed rates as we have used. In our study, particle velocities are higher, probably due to the higher gas temperatures and pressures used, differences in particle size and different particle velocity measuring technique used (PIV vs. PTV).…”

“…[15] have reviewed the gas and particle interactions in cold spraying. Particle velocities has been modelled by using computational fluid dynamics (CFD) models [14,16] and experimentally investigated by using different measuring techniques such as laser-2-focus (L2F) [17], doppler picture velocimetry (DPV) [18][19][20][21], and particle imaging velocimetry (PIV) [22][23][24][25]. Also, we have demonstrated the advanced optical diagnostic method called PTV (particle tracking velocimetry) or S-PTV (sizing-particle tracking velocimetry) [26], which is based on the PIV approach.…”

Influence of Particle Velocity When Propelled Using N2 or N2-He Mixed Gas on the Properties of Cold-Sprayed Ti6Al4V Coatings

“…The optimum particle velocity differs for different types of material due to their different yield strengths and melting points [27,28]. To date, there have been many studies of the influence of particle velocity for different pure metals such as aluminium, copper, and titanium as well as steels [29][30][31][32][33][34][35][36][37][38].…”