Predicting the Effects of Powder Feeding Rates on Particle Impact Conditions and Cold Spray Deposited Coatings
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Predicting the Effects of Powder Feeding Rates on Particle Impact Conditions and Cold Spray Deposited Coatings Ozan C. Ozdemir1 • Christian A. Widener2 • Michael J. Carter2 • Kyle W. Johnson3
Submitted: 26 June 2017 ASM International 2017
Abstract As the industrial application of the cold spray technology grows, the need to optimize both the cost and the quality of the process grows with it. Parameter selection techniques available today require the use of a coupled system of equations to be solved to involve the losses due to particle loading in the gas stream. Such analyses cause a significant increase in the computational time in comparison with calculations with isentropic flow assumptions. In cold spray operations, engineers and operators may, therefore, neglect the effects of particle loading to simplify the multiparameter optimization process. In this study, two-way coupled (particle–fluid) quasi-one-dimensional fluid dynamics simulations are used to test the particle loading effects under many potential cold spray scenarios. Output of the simulations is statistically analyzed to build regression models that estimate the changes in particle impact velocity and temperature due to particle loading. This approach eases particle loading optimization for more complete analysis on deposition cost and time. The model was validated both numerically and experimentally. Further numerical analyses were completed to test the particle loading capacity and limitations of a nozzle with a commonly used throat size. Additional experimentation helped document the physical limitations to high-rate deposition.
& Ozan C. Ozdemir [email protected] 1
Northeastern University, Boston, MA, USA
2
South Dakota School of Mines and Technology, Rapid City, SD, USA
3
VRC Metal Systems, Rapid City, SD, USA
Keywords cold spray particle impact conditions particle injection rate powder feeding rate powder loading rate List of symbols A (m2) Cross-sectional area of flow A (m2) Flow cross-sectional area at nozzle throat C Fitting constant cpp [J/ Particle heat capacity (kg K)] Nozzle exit diameter de (m) dmin (lm) Minimum particle diameter dmax (lm) Maximum particle diameter Frequency-based size distribution dfreq parameter Frequency-based size distribution dvol parameter DE (%) Deposition efficiency dp (m) Particle diameter e (J/kg) Internal energy g Ratio of impact velocity to critical velocity ER Expansion ratio fCD Log-normal cumulative distribution function FD (N) Particle drag force Fp (N) Total particle drag force c Specific heat ratio hp [W/ Heat transfer coefficient (m2 K)] kg [W/ Gas thermal conductivity (m2 K)] Particle thermal conductivity kp [W/ 2 (m K)] Expansion region length Lex (m)
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J Therm Spray Tech
Lshock (m) Ma Mae Mas MMD (m) mp (kg) m_ g (kg/s) m_ p [kg/(m s)] l (kg/s) Np Nu x (%) xc (%) Q_ p (W) Pg (Pa) Pr P0 (Pa) R [J/(kg K)] qg (kg/m3) qp (kg/m3) SoD (m) rult (Pa) rfreq rvol uc (m/s) ue (m/s) ug (m/s) up (m/s) upi (m/s) upave (m/s) T0 (K) Tg (K) Tp (K) Tpi (K)
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