Design of a New Nozzle for Direct Current Plasma Guns with Improved Spraying Parameters

Liu²,

Luo

2019

JMMP

Titanium and its alloys are often used for corrosion protection because they are able to offer high chemical resistance against various corrosive media. In this paper, shrouded plasma spray technology was applied to produce titanium coatings. A solid shroud with an external shrouding gas was used to plasma spray titanium powder feedstock with aim of reducing the oxide content in the as-sprayed coatings. The titanium coatings were assessed by optical microscope, scanning electron microscopy, X-ray diffraction, LECO combustion method and Vickers microhardness testing. The results showed that the presence of the shroud and the external shrouding gas led to a dense microstructure with a low porosity in the plasma-sprayed titanium coatings. The oxygen and nitrogen contents in the titanium coating were kept at a low level due to the shielding effect of the shroud attachment and the external shrouding gas. The dominant phase in the shrouded titanium coatings was mainly composed of α-Ti phase, which was very similar to the titanium feedstock powders. The shrouded plasma-sprayed titanium coatings had a Vickers microhardness of 404.2 ± 103.2 HV.

Section: Titanium Coating Analysismentioning

confidence: 99%

“…The shrouded plasma spray process uses an attachment to shield the plasma jet as it exits the torch. An external gas shroud envelops the plasma jet as it leaves the attachment [13][14][15][16][17][18]. This is expected to be a cost effective method to produce titanium coatings with low oxide content.…”

Section: Introductionmentioning

confidence: 99%

Microstructural Characterization of Shrouded Plasma-Sprayed Titanium Coatings

Liu²,

Luo

2019

JMMP

“…The shroud attachment physically shields the plasma flame as it exits the plasma gun. Meanwhile, an inert gas from the end of the shroud attachment is introduced to envelops the plasma flame, which isolates the molten particles from encountering oxygen from the ambient air [16][17][18][19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Effect of Shroud in Plasma Spraying on Chemical Composition and Thickness of Titanium Coatings

Peng

2021

Coatings

Titanium and its alloys are wildly used in industries. Shrouded plasma spray can be considered as a useful technology to produce low oxide containing titanium coatings. In this paper, the effect of shroud in plasma spraying on chemical composition and thickness of titanium coatings were investigated. Shrouded plasma-sprayed titanium coatings were deposited onto mild steel substrates. Air plasma-sprayed titanium coatings were also deposited for comparison under the same spraying parameters. Those titanium coatings were then studied in terms of microstructure, oxygen and nitrogen contents and coating’s thickness. The titanium coatings were assessed by scanning electron microscopy and quantitative chemical analysis. The results showed that the shroud played a key role in protecting the particles from oxidation in flight. The shrouded titanium coatings exhibited lower oxygen content and an enhanced microstructure. The reduction in air entrainment with the shroud resulted in better heating of the particles and increases in deposition efficiency and coating thickness.

“…Shrouded plasma spray can be considered as a useful technology to produce low oxygen containing titanium coatings. This is to modify plasma spray torches by using an attachment onto an atmospheric plasma spraying torch [11][12][13][14]. In this work, plasma spraying of titanium has been carried out by using a shroud in order to shield molten particles from reacting with surrounding environment.…”

Section: Introductionmentioning

confidence: 99%

Microstructure and Phase Composition of Titanium Coatings Plasma Sprayed with a Shroud

Luo

2018

MATEC Web Conf.

Abstract. Excellent corrosion resistance has made titanium a preferred material for use in industry with harsh environments. Protective titanium coatings combined with cheap bulk materials are expected to enable sufficient corrosion protection and lower the cost. Plasma spray processing of titanium feedstock becomes a challenging topic of research as titanium powder particles have to experience high temperatures in the flight during the thermal spraying process in an open air environment. In this paper, plasma spraying of titanium has been carried out by using a shroud in order to shield molten particles from reacting with surrounding environment. Microstructure analyses on the titanium coatings were performed by using SEM, EDS and XRD. The results show that the shroud attachment is capable of withstanding high plasma temperatures; the as-sprayed shrouded titanium coating exhibits a similar phase composition as the pure titanium powder, and an enhanced microstructure with a lower porosity for the titanium coating plasma-sprayed with a shrouding system is observed.