Emergence and impact of Al2TiO5 in Al2O3-TiO2 APS coatings

Richter, Alexei; Berger, Lutz‐Michael; Conze, Susan; Sohn, Yoo Jung; Vaßen, Robert

doi:10.1088/1757-899x/480/1/012007

Cited by 13 publications

(16 citation statements)

References 37 publications

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“…Similar porosity values were found for all the coatings. They are in the range of results reported in other papers for coatings with similar chemical composition [14,31]. The porosity of the coatings was relatively low, as indicated by the results presented in Figure 6.…”

Section: Coating Microstructuresupporting

confidence: 83%

“…The motivation of studies on the abovementioned powder stems from the fact that, despite numerous studies and years of industrial applications of such APS coatings, surprisingly there are still still unknown issues [14]. This comes from insufficient attention addressed to the used feedstock powder.…”

Section: Introductionmentioning

confidence: 99%

“…This comes from insufficient attention addressed to the used feedstock powder. Most of the studies present the comparison of coatings made from (i) various nanostructured powders (reconstituted into sprayable micrometric agglomerates) and well-known (ii) Metco 130 powder (in cladded form) [2,11,[14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

“…Another important issue, is still a lack of understanding about the influence of formation of aluminum titanate (Al2TiO5) on the microstructure and mechanical properties of Al2O3-13 wt % TiO2 coatings [14]. Therefore, in the presented studies, AT13 coatings, derived from agglomerated and sintered powder, were sprayed according to the 2 k + 1 design of experiment and analyzed in the terms of their morphology, microstructure, phase composition and resulting mechanical and wear properties, including: adhesion, microhardness, fracture toughness (Kc) and sliding wear resistance.…”

Section: Introductionmentioning

confidence: 99%

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The Microstructure and Selected Mechanical Properties of Al2O3 + 13 wt % TiO2 Plasma Sprayed Coatings

et al. 2020

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The Al2O3 + TiO2 coatings are of the interest of surface technology and tribology due to their good wear resistance and enhanced toughness comparing to pure Al2O3 coatings. However, the detailed effect of the used feedstock powder, is often neglected. Here, this work focuses on the deposition of Al2O3 + 13 wt % TiO2 coatings by atmospheric plasma spraying (APS) method as well as on their microstructure, phase composition and selected mechanical properties, in the reference to the route of the powder feedstock preparation. The commercial powder Metco 6221 in agglomerated and sintered form was used as a feedstock material during spraying, due to the fact that, so far, sintered or cladded powders are the most studied ones. The 2k + 1 spray experiment allowed to evaluate the influence of two variables, namely spray distance and torch linear velocity, on the coating microstructure. Afterwards, the coating adhesion was measured by the means of pull-off test. The correlations between Vickers microhardness, fracture toughness (Kc) as well as the coating morphology and phase composition were investigated. Finally, the dry sliding wear resistance was studied by using Ball-on-Disc method.

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Section: Coating Microstructuresupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Microstructure and Selected Mechanical Properties of Al2O3 + 13 wt % TiO2 Plasma Sprayed Coatings

et al. 2020

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“…Although the appearance of hexavalent chromium is below the maximum allowable concentrations under normal process conditions, increased safety regulations are permanently under discussion. By adding Al 2 O 3 [16] or TiO 2 [1,2] to Cr 2 O 3 and forming respective solid solutions, both the formation of hexavalent chromium is suppressed and the deposition efficiency is increased.…”

Section: Introductionmentioning

confidence: 99%

Microstructure and Sliding Wear Resistance of Plasma Sprayed Al2O3-Cr2O3-TiO2 Ternary Coatings from Blends of Single Oxides

et al. 2020

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Al2O3, Cr2O3, and TiO2 are most commonly used oxide materials for thermal spray coating solutions. Each oxide shows unique properties comprising behavior in the spray process, hardness, corrosion, and wear resistance. In order to exploit the different advantages, binary compositions are often used, while ternary compositions are not studied yet. Atmospheric plasma spraying (APS) of ternary compositions in the Al2O3-Cr2O3-TiO2 system was studied using blends of plain powders with different ratios and identical spray parameters. Coatings from the plain oxides were studied for comparison. For these powder blends, different deposition rates were observed. The microstructure, roughness, porosity, hardness, and wear resistance were investigated. The formation of the splats from particles of each oxide occurs separately, without interaction between the particles. The exception are the chromium oxide splats, which contained some amounts of titanium. The predominant oxide present in each blend has a decisive influence on the properties of the coatings. While TiOx causes a low coating porosity, the wear resistance can be increased by adding Cr2O3.

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Changes in the Coating Composition Due to APS Process Conditions for Al2O3-Cr2O3-TiO2 Ternary Powder Blends

et al. 2020

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Thermally sprayed coatings from the single oxides and binary compositions of the Al2O3-Cr2O3-TiO2 system show multifunctional properties. Ternary compositions are promising for further improvement in their performance. The stability of the composition during coating formation is an important issue for blended feedstock powders in order to obtain the desired properties. This work focuses on the compositional changes of a ternary blend of Al2O3, Cr2O3 and TiOx powders of equal content by mass in a conventional atmospheric plasma spraying (APS) process using an Ar/H2 plasma gas mixture. By increasing the argon flow rate at constant hydrogen flow rate, the total plasma gas flow rate and the Ar/H2 ratio were varied. For the highest argon flow rate, this resulted in an average particle velocity of 140% and an average particle temperature of 90% of the initial values, respectively. Coating composition and microstructure were studied by optical microscopy, SEM, including EDS analyses, and XRD. In addition, the coating hardness and electrical impedance were also measured. Differences in the “difficulty of melting factor” (DMF) and the thermal diffusivity of the three oxides appear to be responsible for the dramatic change of the coating composition with an increasing argon flow rate. For the highest argon flow rate applied, besides TiO2, the coating contains only 8 wt.% Al2O3, while the Cr2O3 content remained almost constant. At the same time, the change of the Ar/H2 ratio resulted in the formation of stoichiometric TiO2 in the coating by oxidation of TiOx in the feedstock powder. Moreover, a small content of titanium was found in the Cr2O3 splats, showing that there are only limited interactions between the large oxide powder particles. Thus, the study has shown that stability of the chemical composition during spraying of ternary powder blends is strongly influenced by the process conditions.

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Emergence and impact of Al₂TiO₅ in Al₂O₃-TiO₂ APS coatings

Cited by 13 publications

References 37 publications

The Microstructure and Selected Mechanical Properties of Al2O3 + 13 wt % TiO2 Plasma Sprayed Coatings

The Microstructure and Selected Mechanical Properties of Al2O3 + 13 wt % TiO2 Plasma Sprayed Coatings

Microstructure and Sliding Wear Resistance of Plasma Sprayed Al2O3-Cr2O3-TiO2 Ternary Coatings from Blends of Single Oxides

Changes in the Coating Composition Due to APS Process Conditions for Al2O3-Cr2O3-TiO2 Ternary Powder Blends

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