Formation of Solid Splats During Thermal Spray Deposition

Abstract

This paper reviews the findings of recent research on the formation of solid splats by the impact of thermal spray particles on solid substrates. It discusses methods of describing the substrate, by characterizing both chemical (oxide layers) and physical (surface topography, adsorbed and condensed contaminants) aspects. Recent experiments done to observe impact of thermal spray particle are surveyed and techniques used to photograph particle impact and measure cooling rates described. The use of numerical modeling to simulate impact and deformation of impacting particles is appraised. Two different break-up mechanisms are identified: solidification around the edges of splats; and perforations in the interior of thin liquid films created by droplet spreading without solidification. These two modes can be reproduced in numerical models by varying the value of thermal contact resistance between the splat and substrate. A simple criterion to predict the final splat shape is presented.

Solution and Suspension Plasma Spraying of Nanostructure Coatings

“…The powder mass fraction in suspension was 10 wt%. The suspension was sprayed on a 304L stainless steel substrate preheated with the plasma jet at 300 °C before spraying, to eliminate adsorbates and condensates Chandra and Fauchais (2009). As expected, spray parameters and substrate parameters conditioned the spray bead morphology.…”

Evidence of Substrate Melting of NiCr Particles on Stainless Steel Substrate by Experimental Observation and Simulations

“…The impact of a nickel splat on a stainless steel substrate was simulated using a free surface model with heat transfer and solidification. The solidification and the spreading process of molten splat depended strongly on the thermal contact resistance between the splat and the substrate surface [33][34][35]. It is well-known that thermal contact is a complex function of variety parameters, e.g.…”

“…Instead, a constant value of thermal contact resistance was mostly used in numerical modelling of splat solidification and spreading process. Reported values of thermal contact resistance range widely from 10 -9 to 10 -5 m 2 K/W for different cases from good to poor contact between the splat and the substrate [13,33,35,36].…”

Effect of Substrate Concave Pattern on Splat Formation of Yttria-Stabilized Zirconia in Atmospheric Plasma Spraying

“…Although the surface roughness increases the adhesion strength of the coating to the substrate, it may result in the deterioration of the coating due to the splashing of impinging droplets. Therefore, it is important to fully understand the effect of the surface roughness on the single splat and subsequent coating formations ( Ref 1,2).…”