Detonation spraying is a well-known technology which is applied for deposition of diverse powders, in particular cermets, to form various protective coatings. Actual progress is related to a recently developed technique of computer-controlled detonation spraying and its application in non-traditional domains as development of composite and graded coatings or metallization of plastics. The gas detonation parameters are analyzed to estimate the efficiency of different fuels to vary particle-in-flight velocity and temperature over a broad range thus providing conditions to spray diverse powders. A particle of a given nature and fixed size could be sprayed in a solid state or being strongly overheated above the melting point by variation of the quantity of the explosive gas mixture which is computer-controlled. Particle-inflight velocity and temperature are calculated and compared with jet monitoring by a CCD-camerabased diagnostic tool and experimental data on splats formation.
The aim of this study is to analyze the shape of splats deposited by detonation spraying and correlate splat morphology with the velocity and temperature of particles as they hit the substrate. The obtained results are in good agreement with numerical calculations for nickel splats and show that the thermo-physical properties of composite particles can be estimated from their splat characteristics as well. An understanding of these relationships for various materials is necessary to calculate particle heating in the detonation barrel.
TiB2-43vol.%Cu nanocomposite powders with titanium diboride particle size 50-100 nm
were cold and detonation sprayed in order to fabricate coatings on a copper substrate. The powders
were produced by self-propagating high-temperature synthesis (SHS) followed by mechanical
milling. The temperatures during spraying were calculated and the change in the nanostructure of
the powders during spraying was studied: in cold sprayed coatings the size of TiB2 particles was
well retained, in detonation sprayed coatings the growth of the particles was observed, the mode of
spraying greatly affecting the microstructure and the size of the particles. The hardness of cold
sprayed coatings was higher compared to detonation sprayed coatings. This research shows the
future potential for development of coatings with submicron and nanostructure by cold and
detonation spraying of powders produced by mechanical milling.
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