The adhesion strength of a plasma-sprayed Al2O3 coating with a steel surface was investigated. Various cooling options for this surface were used. It was found that the best result is achieved with active water supply to the spraying zone. The boundaries of the Al2O3 coating and the deposited surface were studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). No evidence of chemical interaction between the Al2O3 coating and the sprayed surface was found. At the same time, quantitative X-ray phase analysis showed that when the water is supplied to the sputtering zone, the phase composition of the Al2O3 coating significantly changes. The amount of α-Al2O3 and δ-Al2O3 decreases ~ 5-fold, and the amount of γ-Al2O3 increases more than 1.5-fold. Given the differences in the physicochemical properties of Al2O3 modifications, this is probably the main reason for the increase in adhesion strength of the Al2O3 coating with a sprayed surface. The technical solutions found were used to form a sublayer of γ-Al2O3, onto which the Al2O3 coating was applied already without water supply to the sputtering zone. The obtained coating had a hardness HV = 821 kgf / mm2. The material of the underlayer and the coating material in the contact zone were a single whole.Keywords: Plasma spraying, Al2O3 coating, adhesion strength, phase composition, structural modifications.
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