High-Velocity Collision of Hot Particles with Solid Substrate Under Detonation Spraying: Detonation Splats

Collision of high-velocity hot particles with a solid substrate is the basic elementary phenomenon in coating formation by thermal spraying. The present paper is the first study to consider the collision of a single particle with the substrate under detonation spraying.
Splats with a size of dozens of microns (particles consolidated with the substrate upon collision) of various metals and cermet composites deposited under a wide range of thermal and dynamic parameters of detonation products are observed. It is found, that not only melted or partially melted particles are bound to the substrate, but as well not-melted ductile particles, which agrees with an earlier conception of bond formation.
Nickel particles are used as a model material, and their parameters are studied at a point in the flow of detonation products corresponding to their melting point. The obtained results are in a good agreement with numerical calculations. Based on the obtained experimental data, empirical parameters of the numerical calculation model are defined more exactly. The possibility to estimate thermo-physical properties of composite materials from splat characteristics is demonstrated. Knowledge of these properties is necessary to calculate particles heating in the detonation barrel.
Splat micro-photographs are used to study deformation characteristics of the bound particles. Peculiarities of splats of composite particles containing refractory carbide grains of a size varying from 10 to 0.1 μm are analyzed.
The obtained results present a significant step forward in the understanding of the process of detonation coating formation.