Effect of Flame Spray Deposition Parameters on The Microstructure of Al2 O3 - 13 %TiO2 Coatings Applied Onto 7075 Aluminum Alloy

Abstract

In this work, the effect of flame spraying parameters on physical, structural and microstructural characteristics of Al 2 O 3-13 wt.% TiO 2 (AT-13) coatings were studied. NiCrAl and AT-13 feedstock powders were used for spraying a bond coat (BC) and a top coat (TC), respectively, onto a 7075 aluminum alloy substrate. The effect of acetylene-to-oxygen ratio and the spraying distance on surface roughness, crystalline phases, porosity and thickness of top coat were analyzed. The results showed that for the evaluated spraying conditions, the volumetric oxy-fuel ratio had significant effects on roughness, porosity and crystalline phases of the coating. On the other hand, the spraying distance affected the thickness of the coating and did not influence the formation of Al 2 TiO 5 phase; no significant effect of spraying distance on roughness was observed. The results showed that an acetylene: oxygen volumetric ratio of 1:2.5 is preferable to obtain higher melting of the ceramic powders and therefore a denser coating with major content of γ-Al 2 O 3 crystalline phase.

Microstructure, phase and dielectric strength of thermally sprayed alumina layers in coating‐based heating systems

“…The standard error of all porosity values was reported to be approximately 0.5. The observed change in porosity is believed to be due to the rise in the oxygen to fuel ratio from 1.2 for FS (2) to 1.6 for FS (1) 37 . A lower amount of porosity in FS (1) alumina is attributed to its oxygen to fuel ratio being closer to its stoichiometric mole ratio and consequently leading to greater deformability and formation of flatter splats.…”

Toward Ceramic Anticorrosion Coatings: A Review

“…The short spray distance ensures that the particles collide in the molten state, resulting in a compact structure, 42 while long spraying distance will thicken the coating, reducing the cohesion and residual stress of the coatings. [43][44] For general flame spraying, the spraying speed is limited, and the prepared coatings usually have large grain size as well as cracks. Therefore, scientists have proposed a high velocity oxy-fuel spraying (HVOF) technology.…”

Use of Different Process Gases for Manufacturing Isolating Alumina Coatings by Flame Spraying with Cords

“…In other studies, a mixture of Al 2 O 3 and TiO 2 was flame-sprayed, showing that the phase composition partially correlated with oxy-fuel ratio. However, these coatings still were mainly composed of gamma phase (Ref 16 ).…”