TRY-OUT OF SPRAYING MODES AND PROPERTIES OF WEAR RESISTANT Al2O3–TiO2 FLAME COATINGS OBTAINED USING FLEXIBLE CORD MATERIAL

Al₂O₃–TiO₂-based coating specimens were obtained using the method of oxyfuel gas spraying of a flexible cord. The paper studies the influence of process parameters and  composition of the sprayed material on  the structure, composition and  mechanical properties of coatings. It was shown that the increase in spraying distance and  feed rate of the sprayed material leads to reduction in their density. An increased concentration of the  low-melting TiO₂ component preconditions a decrease in coating porosity and has no significant effect on its hardness. During measuring scratching, the Al₂O₃–TiO₂ flame coatings formed with minimal porosity (porosity ~ 3,2 %) are characterized by cohesive fracture behavior and no substrate break up at the 90 N load applied to the indenter. The studied coatings show changes in their friction factor from  0,2  to 0,78  after 2800 counterbody revolutions (44  m of rubbing path). This is due to accumulated fatigue cracks in the coating material and  its subsequent cohesive fracture through formation of large fragments that serve as an abrasive.

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