Abstract
This study is aimed at obtaining a coating of aluminum oxide containing α-Al2O3 as the main phase by detonation spraying, as well as a comparative study of the structural, tribological and mechanical properties of coatings with the main phases of α-Al2O3 and γ-Al2O3. It was experimentally revealed for the first time that the use of propane as a combustible gas and the optimization of the technological regime of detonation spraying leads to the formation of an aluminum oxide coating containing α-Al2O3 as the main phase. Tribological tests have shown that the coating with the main phase of α-Al2O3 has a low value of wear volume and coefficient of friction in comparison with the coating with the main phase of γ-Al2O3. It was also determined that the microhardness of the coating with the main phase of α-Al2O3 is 25% higher than that of the coatings with the main phase of γ-Al2O3. Erosion resistance tests have shown (evaluated by weight loss) that the coating with α-Al2O3 phase is erosion-resistant compared to the coating with γ-Al2O3 (seen by erosion craters). However, the coating with the main phase of γ-Al2O3 has a high value of adhesion strength, which is 2 times higher than that of the coating with the main phase of α-Al2O3. As the destruction of coatings by the primary phase, α-Al2O3 began at low loads than the coating with the main phase γ-Al2O3. The results obtained provide the prerequisites for the creation of wear-resistant, hard and durable layered coatings, in which the lower layer has the main phase of γ-Al2O3, and the upper layer has the main phase of α-Al2O3.
Highlights
Alumina coatings have been widely applied in aviation, aerospace, energy, transportation, national defense and other industries for their remarkable characteristics, such as high hardness, heat insulation, anti-wear, thermostability, anti-oxidation and corrosion resistance [1,2,3]
In order to obtain coatings having the main phase of α-Al2 O3, we carried out a series of experiments in various modes of detonation spraying
The results showed that despite the fact that the initial powder was from α-Al2 O3, γ-Al2 O3 phases were formed after spraying using an acetylene-oxygen mixture
Summary
Alumina coatings have been widely applied in aviation, aerospace, energy, transportation, national defense and other industries for their remarkable characteristics, such as high hardness, heat insulation, anti-wear, thermostability, anti-oxidation and corrosion resistance [1,2,3]. The phase composition of an alumina coating depends on the application method, process parameters, substrate temperature, spray particle size and a number of other factors These coatings are obtained by microarc oxidation [4,5], anodic oxidation [6,7], sol–gel [8,9], plasma [10,11], flame [2,12,13] and detonation spraying [14,15]. Our earlier studies [22,23,24] showed that when changing the technological modes (firing frequency, barrel filling volume) of detonation spraying, the ratio of the α-Al2 O3 and γ-Al2 O3 phases changes In these studies [22,23,24], α-Al2 O3 was used as the initial powder, and the maximum possible parameters (frequency of firing and barrel filling) of the CCDS-2000 detonation unit were studied using an acetylene–oxygen mixture. We are trying to obtain a ceramic coating containing α-Al2 O3 as the main phase by detonation spraying, changing the composition of the combustible mixture and comparing the structure and properties of two coatings having the main phases of α-Al2 O3 and γ-Al2 O3
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