Abstract
It is widely held that most oxidation in thermally sprayed coatings occurs on the surface of the droplet after it has flattened. Evidence in this paper suggests that, for the conditions studied here, oxidation of the top surface of flattened droplets is not the dominant oxidation mechanism. In this study, a mild steel wire (AISI 1025) was sprayed using a high-velocity oxy-fuel (HVOF) torch onto copper and aluminum substrates. Ion milling and Auger spectroscopy were used to examine the distribution of oxides within individual splats. Conventional metallographic analysis was also used to study oxide distributions within coatings that were sprayed under the same conditions. An analytical model for oxidation of the exposed surface of a splat is presented. Based on literature data, the model assumes that diffusion of iron through a solid FeO layer is the rate limiting factor in forming the oxide on the top surface of a splat. An FeO layer only a few nanometers thick is predicted to form on the splat surface as it cools. However, experimental evidence shows that the oxide layers are typically 100× thicker than the predicted value. These thick oxide layers are not always observed on the top surface of a splat. Indeed, in some instances the oxide layer is on the bottom, and the metal is on the top. The observed oxide distributions are more consistently explained if most of the oxide forms before the droplets impact the substrate.
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S.E. Hartfield-Wunsch and S.C. Tung, The Effect of Microstructure on the Wear Behavior of Thermal Spray Coatings, Thermal Spray Industrial Applications, C.C. Berndt and S. Sampath, Ed., ASM International, 1994, p 19–24
W.D. Swank, J.R. Fincke, D.C. Haggard, G. Irons, and R. Bullock, HVOF Particle Flow Field Characteristics, Thermal Spray Industrial Applications, C.C. Berndt and S. Sampath, Ed., ASM International, 1994, p 319–324
G.K. Creffield, M.A. Cole, and G.R. White, The Effect of Gas Parameters on HVOF Coatings, Thermal Spray Science & Technology, C.C. Berndt and S. Sampath, Ed., ASM International, 1995, p 291–296
C.M. Hackett and G.S. Settles, Research on HVOF Gas Shrouding for Coating Oxidation Control, Thermal Spray Science & Technology, C.C. Berndt and S. Sampath, Ed., ASM International, 1995, p 21–29
C.M. Hackett and G.S. Settles, Turbulent Mixing of the HVOF Thermal Spray and Coating Oxidation, Thermal Spray Industrial Applications, C.C. Berndt and S. Sampath, Ed., ASM International, 1994, p 19–24
K. Korpiola, J.-P. Hirvonen, H. Jalkanen, L. Lass, and F. Rossi, Oxygen Partial Pressure Measurement in the HVOF Gun Tail Flame, Thermal Spray Science & Technology, C.C. Berndt and S. Sampath, Ed., ASM International, 1995, P 181–185
A. Vardelle, P. Fauchais, and N.J. Themelis, Oxidation of Metal Droplets in Plasma Sprays, Thermal Spray Science & Technology, C.C. Berndt and S. Sampath, Ed., ASM International, 1995, p 175–180
R.A. Neiser, J.E. Brockmann, T.J. O’Hern, R.C. Dykhuizen, M.F. Smith, T.J. Roemer, and R.E. Teets, Wire Melting and Droplet Atomization in a HVOF Jet, Thermal Spray Science & Technology, C.C. Berndt and S. Sampath, Ed., ASM International, 1995, p 99–104
G.J. Shubat, M.B. Bever, and T. Lyman, Ed., Metals Handbook, 8th ed., Vol 8, ASM International, 1973, p 304
A.R. Lopez, B. Hassan, W.L. Oberkampf, R.A. Neiser, T.J. Roemer, Computational Fluid Dynamics of a Wire-Feed, High-Velocity Oxygen-Fuel (HVOF) Thermal Spray Torch, Thermal Spray: Practical Solutions for Engineering Problems, C.C. Berndt, Ed., ASM International, 1996, p 531–540
R.A. Neiser, J.E. Brockmann, T.J. O’Hern, R.C. Dykhuizen, M.F. Smith, T.J. Roemer, and R.E. Teets, Wire Melting and Droplet Atomization in an HVOF Jet, Thermal Spray Science & Technology, C.C. Berndt and S. Sampath, Ed., ASM International, 1995, p 99–104
D. Briggs and M.P. Seah, Ed., Practical Surface Analysis by Auger and X-Ray Photoelectron Spectroscopy, John Wiley & Sons, 1983, p 213
N. Birks and G.H. Meier, Introduction to High Temperature Oxidation of Metals, Edward Arnold Ltd., London, 1983
P. Kofstad, High Temperature Oxidation of Metals, John Wiley & Sons, 1966
L. Himmel, R.F. Mehl, and C.E. Birchenall, Self Diffusion of Iron in Iron Oxides and the Wagner Theory of Oxidation, Trans. AIME, 197, 1953, p 827
G.V. Samsonov, The Oxide Handbook, IFI/Plenum, 1973
S. Fantasi, M. Vardelle, A. Vardelle, and P. Fauchais, Influence of the Velocity of Plasma Sprayed Particles on the Splat Formation, Thermal Spray Research, Design and Applications, C.C. Berndt and T.F. Bernecki, Ed., ASM International, 1993, p 1–6
C. Moreau, P. Cielo, M. Lamontagne, Flattening and Solidification of Thermal Sprayed Particles, Thermal Spray: International Advances in Coatings Technology, C.C. Berndt, Ed., ASM International, 1992, p 761–766
C. Moreau, M. Lamontagne, P. Cielo, Influence of the Coating Thickness on the Cooling Rate of Plasma-Sprayed Particles Impinging on a Substrate, Thermal Spray Coatings: Properties, Processes and Applications, T.F. Bernecki, Ed., ASM International, 1991, p 237–243
B.P. LeClair, A.F. Hamilee, H.R. Pruppacher, and W.D. Hall, A Theoretical and Experimental Study of the Internal Circulation in Water Drops Falling at Terminal Velocity in Air, J. Atmospheric Sciences, 29, 1972, p 728–740
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Neiser, R.A., Smith, M.F. & Dykhuizen, R.C. Oxidation in wire HVOF-sprayed steel. J Therm Spray Tech 7, 537–545 (1998). https://doi.org/10.1361/105996398770350765
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DOI: https://doi.org/10.1361/105996398770350765