Deposition and characterization of Al2O3 coatings by multi-chamber gas-dynamic accelerator

A series of Al2O3 coatings have been prepared on steel substrate by multi-chamber gas-dynamic accelerator. The coatings (200 μm thick) were deposited in 6 passes in the three modes at different nozzle lengths (300, 400, 500 mm) of multi-chamber gas-dynamic accelerator. The Al2O3 coatings microstructures and phase compositions were characterised using SEM, TEM, OM and XRD techniques. The hardness tests were carried out by the Vickers method under loads on the indenter equal to 25 and 300 g. The dense ceramic layers with hardness of 1100 ± 100 HV0.3 and porosity of less than 1% have been prepared by multi-chamber gas-dynamic accelerator with a nozzle length of 500 mm. The micro-hardness of substrate under the coating to a depth of 200 μm changes from 400 HV0.3 to an average hardness of the specimen material equal to 346 HV0.3. The intermetallic compound type of FeAl was revealed in the area of the coating that adjoins to the substrate (TEM/electron diffraction).