Review of impact and solidification of molten thermal spray droplets

The unique properties of coatings created by thermal spray deposition depend on the rapid solidification of individual splats created by impinging molten droplets. However, the impact process has been little studied because of the difficulty of measuring or numerically simulating the process, which occurs very quickly over a small area. Other scientific fields have investigated the impact of liquid droplets on solid surfaces. This paper reviews these studies, along with those conducted specifically on the thermal spray process. Modelers have almost universally ignored droplet solidification during impact; however, some experimental evidence suggests that the solidification process plays a significant role in splat formation. Splashing of impacting liquid droplets, another topic that has been largely ignored, affects deposition efficiency, porosity, and bond strength, and may also affect the amount of oxides incorporated in the coating. The scaling of data from impacting millimeter-size droplets traveling at low velocities to thermal spray conditions is questioned.

[1]  P. Hobbs,et al.  Splashing of water drops on solid and wetted surfaces: hydrodynamics and charge separation , 1971, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[2]  C. Moreau,et al.  Influence of the coating thickness on the cooling rates of plasma-sprayed particles impinging on a substrate☆ , 1992 .

[3]  D. R. Mash,et al.  Process Variables in Plasma-Jet Spraying , 1961 .

[4]  J. Wood,et al.  Experimental observations of crystal growth in alloys rapidly quenched from the liquid state , 1975 .

[5]  C. Stow,et al.  The Physical Products of a Splashing Water Drop , 1977 .

[6]  Lung. Cheng.  Dynamic Spreading of Drops Impacting onto a Solid Surface , 1977 .

[7]  Jm Jos Houben.  Relation of the adhesion of plasma sprayed coatings to the process parameters size, velocity and heat content of the spray particles , 1988 .

[8]  H. Herman,et al.  4 - Plasma-Sprayed Materials , 1981 .

[9]  Francis H. Harlow,et al.  The Splash of a Liquid Drop , 1967 .

[10]  E. B. Dussan,et al.  LIQUIDS ON SOLID SURFACES: STATIC AND DYNAMIC CONTACT LINES , 1979 .

[11]  J. Madejski,et al.  Solidification of droplets on a cold surface , 1976 .

[12]  H. Jones,et al.  REVIEW ARTICLE: Cooling, freezing and substrate impact of droplets formed by rotary atomization , 1971 .

[13]  T. W. Clyne.  Numerical treatment of rapid solidification , 1984 .

[14]  Takayuki Watanabe,et al.  Deformation and solidification of a droplet on a cold substrate , 1992 .

[15]  I. A. Fisher,et al.  Variables Influencing the Characteristics of Plasma-Sprayed Coatings , 1972 .

[16]  C. Avedisian,et al.  On the collision of a droplet with a solid surface , 1991, Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences.

[17]  S. E. Hinkle.  Water Drop Kinetic Energy and Momentum Measurement Considerations , 1989 .

[18]  J. Zaat.  A Quarter of a Century of Plasma Spraying , 1983 .

[19]  D. Apelian,et al.  Melting and solidification in plasma spray deposition — phenomenological review , 1983 .

[20]  Gerardo Trapaga,et al.  Mathematical modeling of the isothermal impingement of liquid droplets in spraying processes , 1991 .

[21]  Roger H. Rangel,et al.  Numerical simulation of substrate impact and freezing of droplets in plasma spray processes , 1993 .

[22]  S. Suresh,et al.  Mechanisms of Slow Fatigue Crack Growth in High Strength Aluminum Alloys: Role of Microstructure and Environment , 1984 .

[23]  P. Fauchais,et al.  Influence of the velocity of plasma-sprayed particles on splat formation , 1993 .

[24]  J. C. Jaeger,et al.  Conduction of Heat in Solids , 1952 .

[25]  J. Szekely,et al.  Fluid flow, heat transfer, and solidification of molten metal droplets impinging on substrates: Comparison of numerical and experimental results , 1992 .

[26]  R. Dykhuizen,et al.  An investigation of the effects of droplet impact angle in thermal spray deposition , 1994 .

[27]  D. G. Moore,et al.  STUDIES OF THE PARTICLE-IMPACT PROCESS FOR APPLYING CERAMIC AND CERMET COATINGS. Funal Summary Report , 1961 .

[28]  O. G. Engel,et al.  Waterdrop collisions with solid surfaces , 1955 .

[29]  F. J. Heymann,et al.  High‐Speed Impact between a Liquid Drop and a Solid Surface , 1969 .

[30]  C. Stow,et al.  An experimental investigation of fluid flow resulting from the impact of a water drop with an unyielding dry surface , 1981, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[31]  A. Riddiford,et al.  Dynamic contact angles , 1967 .

[32]  A. R. Lang.  The early days of high-resolution X-ray topography , 1993 .

[33]  F. G. Hammitt,et al.  Hydrodynamic Phenomena During High-Speed Collision Between Liquid Droplet and Rigid Plane , 1973 .

[34]  T. Elliott,et al.  Dynamic contact angles. Part 7.—Impact spreading of water drops in air and aqueous solutions of surface active agents in vapour on smooth paraffin wax surfaces , 1972 .

[35]  Jack Louis Zable,et al.  Splatter during ink jet printing , 1977 .

[36]  R. C. Weast.  CRC Handbook of Chemistry and Physics , 1973 .