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

Abstract This study assesses the quality of flame-sprayed alumina coatings produced from recently developed alumina cord using argon and compressed air as atomizing gases. Coatings of different thicknesses were deposited on aluminum substrates and then analyzed using optical microscopy, X-ray diffraction, and resistivity measurements. The coatings, particularly those sprayed with argon, had fine microstructure and higher surface and volume resistivity than flame-spray coatings made from alumina cord in the past. They were also found to have higher alpha phase content than plasma-sprayed coatings, regardless of the atomizing gas used. The effect of humidity and the possible formation of aluminum hydroxides are also addressed.

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

Journal of Thermal Spray Technology ◽

10.1007/s11666-021-01160-8 ◽

2021 ◽

Vol 30 (1-2) ◽

pp. 222-235

Author(s):

Michél Hauer ◽

Melanie Meyer ◽

Dominique Billieres ◽

Cédric Bricquet ◽

Franz Gerstgrasser ◽

...

Keyword(s):

Phase Composition ◽

Volume Resistivity ◽

Cost Effective ◽

Alpha Phase ◽

Flame Spraying ◽

Alumina Coatings ◽

Innovative Products ◽

Plasma Sprayed Coatings ◽

Plasma Sprayed ◽

Sprayed Coatings

AbstractBesides conventional industrial demands, thermally sprayed coatings are increasingly used for innovative products. Such an application is the additive manufacturing of electrical components in automotive engineering. In particular, heating units are currently manufactured by a combination of various spray technologies. At present, simpler spraying processes like flame spraying are investigated with regard to their suitability as a future cost-effective alternative for fabricating isolating alumina coatings. In the present study, alumina cords were flame-sprayed using compressed air and argon as atomizing gases. The results demonstrate finely dispersed microstructures and a more regular and partially even higher surface and volume resistivity compared to past investigations in the literature as well as conventionally plasma-sprayed coatings despite a significantly reduced coating thickness. The content of alpha phase is clearly higher than for plasma-sprayed coatings, regardless of the atomizing gas used. Moreover, flame-sprayed coatings using argon reveal a higher resistivity in comparison to coatings sprayed with air. While the atomizing gas is found to mainly influence the ideal stand-off distance, the phase composition is not changed severely. In addition to the phase composition and kinematics, it can finally be concluded that humidity plays a major role in the coating properties.

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Alumina Coatings by Plasma Spraying of Monosize Sapphire Particles

Thermal Spray 1998: Proceedings from the International Thermal Spray Conference ◽

10.31399/asm.cp.itsc1998p0791 ◽

1998 ◽

Author(s):

L.C. Erickson ◽

T. Troczynski ◽

H.M. Hawthorne ◽

H. Tai ◽

D. Ross

Keyword(s):

High Hardness ◽

Processing Parameters ◽

Raw Material ◽

Splat Morphology ◽

Alumina Coatings ◽

Spray Coatings ◽

Dense Microstructure ◽

Plasma Sprayed Coatings ◽

Plasma Sprayed ◽

Sprayed Coatings

Abstract In an effort to obtain a series of plasma sprayed coatings of controlled microstructure, three mono-sized sapphire powders were deposited using an axial injection torch in which the plasma gas composition and nozzle diameter were the only processing parameters varied. The effects of changes in these parameters on the resultant coating splat morphology, porosity, angular crack distribution and hardness are reported. The uniform, dense microstructure and high hardness of 14 GPa - a level usually only associated with chromia thermal spray coatings - of the best alumina coatings results from use of the combination of tightly controlled processing conditions and mono-disperse precursor powders. The microstructural quality of plasma sprayed coatings and, hence, their properties can be improved significantly by minimizing variations in processing and raw material parameters.

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Microstructure and mechanical properties of alumina coatings plasma-sprayed at different substrate temperatures

Acta Mechanica Solida Sinica ◽

10.1016/s0894-9166(11)60045-1 ◽

2011 ◽

Vol 24 (5) ◽

pp. 461-466 ◽

Cited By ~ 9

Author(s):

Yazhe Xing ◽

Chaoping Jiang ◽

Hong Chen ◽

Jianmin Hao

Keyword(s):

Mechanical Properties ◽

Alumina Coatings ◽

Microstructure And Mechanical Properties ◽

Plasma Sprayed ◽

Substrate Temperatures

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Surface Wear Improvement of Al-Alloys by Amorphous Iron-Based Flame-Sprayed Coatings

Materials Science Forum ◽

10.4028/www.scientific.net/msf.690.405 ◽

2011 ◽

Vol 690 ◽

pp. 405-408 ◽

Cited By ~ 2

Author(s):

Joel Voyer

Keyword(s):

Wear Resistance ◽

Flame Spraying ◽

Flame Spray ◽

Phase Content ◽

Coating Properties ◽

Amorphous Iron ◽

Spray Process ◽

Spraying Parameters ◽

Iron Based ◽

Sprayed Coatings

Partially amorphous iron-based coatings were produced onto aluminium using a powder flame-spraying process with a commercially available feedstock powder (Nanosteel SHS-7170) obtained from the Nanosteel Company Inc.. Several coating properties such as the microstructure, porosity, phase content, micro-hardness, and wear resistance were evaluated in the as-sprayed condition. As shown by the results obtained, the powder flame iron-based coatings perform relatively well in term of wear resistance in comparison with similar coatings produced using other expensive thermal spray techniques. Furthermore, this study shows that all the coating properties (microstructure, porosity, phase content, hardness and wear performance) depend strongly on the flame spraying parameters used. Finally, this paper demonstrates clearly that the flame-spray process may be used to produce amorphous iron-based coatings having a good wear resistance, and that this process appears to be a suitable inexpensive alternative to plasma or HVOF processes based on the present results.

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Ultrasonic technique for measuring porosity of plasma-sprayed alumina coatings

Journal of Thermal Spray Technology ◽

10.1007/s11666-997-0035-3 ◽

1997 ◽

Vol 6 (4) ◽

pp. 486-488 ◽

Cited By ~ 7

Author(s):

S. Parthasarathi ◽

B. R. Tittmann ◽

E. J. Onesto

Keyword(s):

Ultrasonic Technique ◽

Alumina Coatings ◽

Plasma Sprayed

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Mechanism of plastic deformation in formation of flame spray coatings

Soviet Powder Metallurgy and Metal Ceramics ◽

10.1007/bf00794555 ◽

1988 ◽

Vol 27 (12) ◽

pp. 947-952

Author(s):

Yu. A. Kharlamov

Keyword(s):

Plastic Deformation ◽

Flame Spray ◽

Spray Coatings

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GTAW-Pulsed Refusion Patterns of NiCrBSi Thermal Sprayed Coatings

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.813.304 ◽

2019 ◽

Vol 813 ◽

pp. 304-309

Author(s):

Alejandro Oscar Miranda ◽

Hernán Gabriel Svoboda

Keyword(s):

Steel Substrate ◽

Base Material ◽

Travel Speed ◽

Flame Spray ◽

Surface Appearance ◽

Spray Coatings ◽

Electrode Distance ◽

Gas Tungsten Arc ◽

Coating Characteristics ◽

Welding Procedure

NiCrBSi coatings were produce by Flame Spray on a carbon steel substrate. The “as spray” coatings were refused by means of Pulsed Gas Tungsten Arc Welding (GTAW-P) process, following different patterns and welding procedure, with objective of optimize the coating characteristics and productivity. The patterns evaluated were oscillated triangular (OT) and oscillated sinusoidal (OS). Travel speed and workpiece-electrode distance were also analyzed. On each obtained sample the surface appearance, macro and microstructure on transverse cuts were evaluated, determining penetration, dilution and level of defects, among others features. Microhardness profiles and adherence were also evaluated. The OS pattern show a more uniform profile of the refused thickness, with less dilution with the base material. Travel speed and workpiece-electrode distance have both significant effect on the volume of refused material, affecting dilution and consequently the resultant coating hardness.

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A Definition of the Topography of Grit-Blasted Surfaces for Plasma Sprayed Alumina Coatings

Journal of Manufacturing Science and Engineering ◽

10.1115/1.2830574 ◽

1999 ◽

Vol 121 (1) ◽

pp. 49-53 ◽

Cited By ~ 14

Author(s):

B. J. Griffiths ◽

D. T. Gawne ◽

G. Dong

Keyword(s):

Surface Topography ◽

Raw Material ◽

Height Distribution ◽

Alumina Coatings ◽

Definition Of ◽

The Individual ◽

Plasma Sprayed ◽

Individual Particles

This paper describes the topographical implications of grit blasted surfaces on plasma sprayed alumina. The transition of the grit blasted surface from raw material to correctly blasted is described in terms of surface heights, height distribution, spacings and texture. The influence of embedded grit is shown to be significant. The individual particles of alumina impacting the surface are classified into two types, these being disc splats and splash splats. Their deposition relationships with regard to surface topography and adhesion is explained with reference to the two types of splat.

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