scholarly journals A Study on the Microstructural Characterization and Phase Compositions of Thermally Sprayed Al2O3-TiO2 Coatings Obtained from Powders and Water-Based Suspensions

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2638 ◽  
Author(s):  
Monika Michalak ◽  
Filofteia-Laura Toma ◽  
Leszek Latka ◽  
Pawel Sokolowski ◽  
Maria Barbosa ◽  
...  
Keyword(s):  
Phase Composition ◽  
Plasma Spraying ◽  
Microstructural Characterization ◽  
Atmospheric Plasma ◽  
Coating Morphology ◽  
Liquid Feedstock ◽  
Α Al2o3 ◽  
Titania Coatings ◽  
Thermal Spray Processes ◽  
Oxygen Fuel

In this work, the alumina (Al2O3) and alumina-titania coatings with different contents of TiO2, i.e., Al2O3 + 13 wt.% TiO2 and Al2O3 + 40 wt.% TiO2, were studied. The coatings were produced by means of powder and liquid feedstock thermal spray processes, namely atmospheric plasma spraying (APS), suspension plasma spraying (SPS) and suspension high-velocity oxygen fuel spraying (S-HVOF). The aim of the study was to investigate the influence of spray feedstocks characteristics and spray processes on the coating morphology, microstructure and phase composition. The results revealed that the microstructural features were clearly related both to the spray processes and chemical composition of feedstocks. In terms of phase composition, in Al2O3 (AT0) and Al2O3 + 13 wt.% TiO2 (AT13) coatings, the decrease in α-Al2O3, which partially transformed into γ-Al2O3, was the dominant change. The increased content of TiO2 to 40 wt.% (AT40) involved also an increase in phases related to the binary system Al2O3-TiO2 (Al2TiO5 and Al2−xTi1+xO5). The obtained results confirmed that desired α-Al2O3 or α-Al2O3, together with rutile-TiO2 phases, may be preserved more easily in alumina-titania coatings sprayed by liquid feedstocks.

scholarly journals Wear Behavior Analysis of Al2O3 Coatings Manufactured by APS and HVOF Spraying Processes Using Powder and Suspension Feedstocks

Coatings ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 879
Author(s):  
Monika Michalak ◽  
Paweł Sokołowski ◽  
Mirosław Szala ◽  
Mariusz Walczak ◽  
Leszek Łatka ◽  
...  
Keyword(s):  
Plasma Spraying ◽  
Wear Behavior ◽  
Ceramic Coatings ◽  
Suspension Plasma Spraying ◽  
Atmospheric Plasma ◽  
Hvof Spraying ◽  
The Coefficient Of Friction ◽  
Wear Mode ◽  
Α Al2o3 ◽  
Plasma Sprayed

Thermally sprayed ceramic coatings are applied for the protection of surfaces that are exposed mainly to wear, high temperatures, and corrosion. In recent years, great interest has been garnered by spray processes with submicrometric and nanometric feedstock materials, due to the refinement of the structure and improved coating properties. This paper compares the microstructure and tribological properties of alumina coatings sprayed using conventional atmospheric plasma spraying (APS), and various methods that use finely grained suspension feedstocks, namely, suspension plasma spraying (SPS) and suspension high-velocity oxy-fuel spraying (S-HVOF). Furthermore, the suspension plasma-sprayed Al2O3 coatings have been deposited with radial (SPS) and axial (A-SPS) feedstock injection. The results showed that all suspension-based coatings demonstrated much better wear resistance than the powder-sprayed ones. S-HVOF and axial suspension plasma spraying (A-SPS) allowed for the deposition of the most dense and homogeneous coatings. Dense-structured coatings with low porosity (4 vol.%) and good cohesion to the metallic substrate, containing a high content of α–Al2O3 phase (56 vol.%) and a very low wear rate (0.2 ± 0.04 mm3 × 10−6/(N∙m)), were produced with the S-HVOF method. The wear mechanism of ceramic coatings included the adhesive wear mode supported by the fatigue-induced material delamination. Moreover, the presence of wear debris and tribofilm was confirmed. Finally, the coefficient of friction for the coatings was in the range between 0.44 and 0.68, with the highest values being recorded for APS sprayed coatings.

scholarly journals Advanced Coatings by Thermal Spray Processes

Technologies ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 79
Author(s):  
Joshi ◽  
Nylen
Keyword(s):  
Thermal Spray ◽  
High Velocity ◽  
High Performance ◽  
Fine Particles ◽  
Thermal Spraying ◽  
Atmospheric Plasma ◽  
Processing Temperature ◽  
Diverse Application ◽  
Liquid Feedstock ◽  
Thermal Spray Processes

Coatings are pivotal in combating problems of premature component degradation in aggressive industrial environments and constitute a strategic area for continued development. Thermal spray (TS) coatings offer distinct advantages by combining versatility, cost-effectiveness, and the ability to coat complex geometries without constraints of other in-chamber processes. Consequently, TS techniques like high-velocity oxy-fuel (HVOF) and atmospheric plasma spray (APS) are industrially well-accepted. However, they have reached limits of their capabilities while expectations from coatings progressively increase in pursuit of enhanced efficiency and productivity. Two emerging TS variants, namely high-velocity air-fuel (HVAF) and liquid feedstock thermal spraying, offer attractive pathways to realize high-performance surfaces superior to those hitherto achievable. Supersonic HVAF spraying provides highly adherent coatings with negligible porosity and its low processing temperature also ensures insignificant thermal ‘damage’ (oxidation, decarburization, etc.) to the starting material. On the other hand, liquid feedstock derived TS coatings, deposited using suspensions of fine particles (100 nm–5 µm) or solution precursors, permits the production of coatings with novel microstructures and diverse application-specific architectures. The possibility of hybrid processing, combining liquid and powder feedstock, provides further opportunities to fine tune the properties of functional surfaces. These new approaches are discussed along with some illustrative examples.

Environmental Applications of the Reactive Titania Coatings Elaborated by Suspension Plasma Spraying

2006 ◽  
Vol 45 ◽  
pp. 2182-2187
Author(s):  
Filofteia Laura Toma ◽  
Ghislaine Bertrand ◽  
Cathy Meunier ◽  
Sylvie Begin ◽  
Didier Klein ◽  
...  
Keyword(s):  
Plasma Spraying ◽  
Air Pollutants ◽  
Fine Particles ◽  
Suspension Plasma Spraying ◽  
Atmospheric Plasma ◽  
Atmospheric Conditions ◽  
Titania Coatings ◽  
Reactive Surfaces ◽  
Feedstock Material ◽  
Photocatalytic Applications

This paper deals with the elaboration of titanium dioxide coatings, designed for photocatalytic applications, obtained by a non-conventional method of deposition: suspension plasma spraying (SPS). SPS is an alternative of the atmospheric plasma spraying (APS) in which the feedstock material is a suspension of the powder to be sprayed. The method consists in injection and atomization of a slurry (suspension of fine particles in a solvent) in an enthalpic source (plasma). TiO2 P25 powder (Degussa AG) was mechanically dispersed in distilled water and ethanol and injected in Ar-H2 or Ar-H2-He plasma under atmospheric conditions. SEM and XRD were performed to study the microstructure and the crystalline phases of the titania coatings. Photocatalytic efficiency of the elaborated samples was evaluated from the conversion rate of nitrogen oxides. The present results showed that the suspension plasma spraying allows to produce reactive surfaces for the removal of air pollutants, that in the same working conditions, present a higher photocatalytic activity compared to that of the initial raw powders.

Microstructural Characterization of Ni(Co)CrAlY Powders Designed for Thermal Spraying of Bondcoat for TBC Systems

2013 ◽  
Vol 203-204 ◽  
pp. 435-438 ◽  
Author(s):  
Grzegorz Moskal
Keyword(s):  
Phase Composition ◽  
Chemical Composition ◽  
Thermal Spraying ◽  
Microstructural Characterization ◽  
Atmospheric Plasma Spraying ◽  
Atmospheric Plasma ◽  
Microstructural Characteristics ◽  
Study Results ◽  
Tbc Systems

The paper presents the study results concerning microstructural characteristics of the Ni(Co)CrAlY type powders designed for the bondcoat spraying with the plasma method for TBC layers obtained by the atmospheric plasma spraying (APS). Three types of powders with the following chemical composition Ni-23Co-17Cr-12.5Al-0.45Y, Co-32Ni-21Cr-8Al-0.5Y and Ni-22Cr-10Al-Y were subjected to analysis. The assessment of surface morphology and inner structure of powders (SEM) was made. Chemical composition (EDX, OES-ICP) of the powders was determined. Phase composition by using XRD and EBSD methods was also analysed.

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

Coatings ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 173 ◽  
Author(s):  
Monika Michalak ◽  
Leszek Łatka ◽  
Paweł Sokołowski ◽  
Aneta Niemiec ◽  
Andrzej Ambroziak
Keyword(s):  
Mechanical Properties ◽  
Wear Resistance ◽  
Phase Composition ◽  
Atmospheric Plasma ◽  
Dry Sliding Wear ◽  
Coating Morphology ◽  
Coating Microstructure ◽  
Tio2 Coatings ◽  
Feedstock Preparation ◽  
Plasma Sprayed

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.

scholarly journals Columnar Thermal Barrier Coatings Produced by Different Thermal Spray Processes

2021 ◽  
Author(s):  
Nitish Kumar ◽  
Mohit Gupta ◽  
Daniel E. Mack ◽  
Georg Mauer ◽  
Robert Vaßen
Keyword(s):  
Thermal Conductivity ◽  
Plasma Spraying ◽  
Thermal Spray ◽  
Vapor Deposition ◽  
Physical Vapor Deposition ◽  
Deposition Process ◽  
Cyclic Fatigue ◽  
Atmospheric Plasma ◽  
Plasma Sprayed ◽  
Thermal Spray Processes

AbstractSuspension plasma spraying (SPS) and plasma spray-physical vapor deposition (PS-PVD) are the only thermal spray technologies shown to be capable of producing TBCs with columnar microstructures similar to the electron beam-physical vapor deposition (EB-PVD) process but at higher deposition rates and relatively lower costs. The objective of this study was to achieve fundamental understanding of the effect of different columnar microstructures produced by these two thermal spray processes on their insulation and lifetime performance and propose an optimized columnar microstructure. Characterization of TBCs in terms of microstructure, thermal conductivity, thermal cyclic fatigue lifetime and burner rig lifetime was performed. The results were compared with TBCs produced by the standard thermal spray technique, atmospheric plasma spraying (APS). Bondcoats deposited by the emerging high-velocity air fuel (HVAF) spraying were compared to the standard vacuum plasma-sprayed (VPS) bondcoats to investigate the influence of the bondcoat deposition process as well as topcoat–bondcoat interface topography. The results showed that the dense PS-PVD-processed TBC had the highest lifetime, although at an expense of the highest thermal conductivity. The reason for this behavior was attributed to the dense intracolumnar structure, wide intercolumnar gaps and high column density, thus improving the strain tolerance and fracture toughness.

scholarly journals Development of Photocatalytic Active TiO2Surfaces by Thermal Spraying of Nanopowders

2008 ◽  
Vol 2008 ◽  
pp. 1-8 ◽  
Author(s):  
Filofteia-Laura Toma ◽  
Ghislaine Bertrand ◽  
Didier Klein ◽  
Cathy Meunier ◽  
Sylvie Begin
Keyword(s):  
Plasma Spraying ◽  
High Performance ◽  
Photocatalytic Performance ◽  
Thermal Spraying ◽  
Environmental Water ◽  
Suspension Plasma Spraying ◽  
Atmospheric Plasma ◽  
Spray Process ◽  
Coating Characteristics ◽  
Titania Coatings

Titanium dioxide is a very useful photocatalyst for the decomposition and diminution of environmental water and air pollutants. In such applications, it can be used as slurry or as immobilized coating obtained by different deposition methods. The studies performed in the last years showed that thermal spraying could be employed to elaborate TiO2coatings with high performance for the decomposition of organic compounds. This manuscript presents a comparative study on the microstructure and photocatalytic performance of titania coatings obtained by different thermal spray techniques: atmospheric plasma spraying (APS), suspension plasma spraying (SPS) and high-velocity oxygen fuel spray process (HVOF). Different titania powders and suspensions were used to study the influence of the feedstock materials on the coating characteristics. The deposits were mainly characterised by SEM and X-ray diffraction. The photocatalytic performance was evaluated from the removal of nitrogen oxides. The experimental results showed that a drastic reduction of the pollutant concentration was obtained in presence of coatings elaborated by suspension plasma spraying. TiO2coatings resulting from the spraying of agglomerated powder presentd less efficiency. That was mainly explained by the significant phase transformation from anatase to rutile that occurred in the enthalpic source during the spray processes.

Consolidation of TiAl Powder by Thermal Spray Processes

2007 ◽  
Vol 29-30 ◽  
pp. 159-162 ◽  
Author(s):  
Peng Cao ◽  
Brian Gabbitas ◽  
Asma Salman ◽  
De Liang Zhang ◽  
Z.H. Han
Keyword(s):  
Plasma Spraying ◽  
Thermal Spray ◽  
Spray Deposition ◽  
Atmospheric Plasma ◽  
Titanium Oxides ◽  
Protective Layers ◽  
Technological Developments ◽  
Powder Particles ◽  
Cold Gas Spraying ◽  
Thermal Spray Processes

Thermal spray deposition has been widely used as a coating process for applying thin protective layers to the need-to-protect materials, or substrates. Recent technological developments in thermal spray processing, particularly cold gas spraying (CGS) and supersonic plasma spraying (S-PS), have enabled some emerging applications for making structural components. This paper reports on the results of our recent attempts to obtain thick TiAl coatings using three coating techniques: atmospheric plasma spraying (APS), S-PS and CGS. We successfully achieved a 3 mm thick coating using both APS and S-PS techniques, but failed in cold spray. A significant phase change was observed of the powder particles experienced during both APS and S-PS processes. Nevertheless, a considerable quantity of titanium oxides was observed in the APS coating.

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