Comparative Study of Structures and Properties of Detonation Coatings with α-Al2O3 and γ-Al2O3 Main Phases

This study is aimed at obtaining a coating of aluminum oxide containing alpha-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 alpha-Al2O3 and gamma-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 alpha-Al2O3 as the main phase. Tribological tests have shown that the coating with the main phase of alpha-Al2O3 has a low value of wear volume and coefficient of friction in comparison with the coating with the main phase of gamma-Al2O3. It was also determined that the microhardness of the coating with the main phase of alpha-Al2O3 is 25% higher than that of the coatings with the main phase of gamma-Al2O3. Erosion resistance tests have shown (evaluated by weight loss) that the coating with alpha-Al2O3 phase is erosion-resistant compared to the coating with gamma-Al2O3 (seen by erosion craters). However, the coating with the main phase of gamma-Al2O3 has a high value of adhesion strength, which is 2 times higher than that of the coating with the main phase of alpha-Al2O3. As the destruction of coatings by the primary phase, alpha-Al2O3 began at low loads than the coating with the main phase gamma-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 gamma-Al2O3, and the upper layer has the main phase of alpha-Al2O3.