Features of detonation coatings AK4-glass

Abstract

The study is aimed at investigating the possibility of applying thermal barrier coatings (TBC), namely the composites with different contents of aluminum alloy AK4 and silicate glass, by the detonation method. High potential for using these composites as TBCs is shown for use under mechanical and thermal loads in combustion engines. The samples were applied using a gas gun with a barrel diameter of 20 mm. Scanning electron microscopy, energy-dispersive X-ray spectral analysis, X-ray powder diffraction and hardness measurement were used to study the coatings. Based on the data obtained, the most promising characteristics are possessed by samples that are composites of glass and aluminum with high density and a smooth surface, in particular, a composite of 25% AK4 with 75% glass (43% barrel filling). This composition has a high glass content, the thickness of the resulting layer is 1.34 mm and a smooth dense surface. These properties make this composition compare favorably with coatings made of pure glass or pure AK4. It is obvious that the two components (metal and glass) act synergistically, reducing the formation of scale, probably due to the increase in the temperature of liquid droplets. It can be assumed that the wider wavelength spectrum of glass radiation in the case of a metal + glass mixture leads to more efficient heating of the metal compared to spraying of pure AK4. When using pure glass, the coating is too non-uniform, brittle, cracked and rough due to the formation of fibrous glass flakes in flight. In terms of gun efficiency (powder absorption up to 30%), the best results were shown by samples of pure AK4 and AK6 and pure glass. The composites also provide acceptable powder absorption (at least 15%). The porosity of the composites is slightly higher than the porosity of the pure components. These composites have a high potential for use as thermal barrier coatings for combustion engines, due to the availability of components and demonstrated characteristics, as well as the possibility of application on an industrial scale.