Pulsed laser glazing

Dallaire, S.; Cielo, P.

doi:10.1016/0040-6090(83)90037-8

Cited by 8 publications

(1 citation statement)

References 6 publications

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“…Bhat et al 14 have sealed pores by melting a thin layer of 20-25 Jlm plasma sprayed NiCrAIY coatings using a CO 2 laser operating in the continuous wave (cw) mode. Some of the above investigations dealt with the effect of laser processing variables, 10,11 while others concentrated on the structure and properties of the laser melted layers. 12 ,14 Dallaire and Cielo 11 quoted the work of Ayers and Schaefer in which a sponge like structure was produced when the air sprayed coatings were melted using a CO 2 laser operating in cw mode.…”

Section: Mcraiymentioning

confidence: 99%

Laser Melting of Plasma Sprayed Nicocraly Coatings

Sivakumar

Mordike

1987

Surface Engineering

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MCrAIYcoatings (M = Ni, Co, Fe alone or in combination) are currently used to protect gas turbine blades and vanes from oxidation and hot corrosion. The coatings are required to be fully dense and well bonded to the substrate. They are formed either by electron beam evaporation or by low pressure plasma spraying. Another possible route is to form them by normal atmospheric plasma spraying, followed by remelting with a laser to remove porosity and other defects. The feasibility of this approach has beenHigh temperature coatings are applied to many gas turbine components to improve their surface properties. Of these, turbine blades and vanes are very critical, since they are subjected to a combination of high stresses and degradation of the surface by oxidation, hot corrosion, and erosion. The current practice is to apply protective coatings based on MCrAIY compositions (M is a transition metal: Ni, Co, or Fe) to extend the life and reliability of these components. 1, 2 Depending upon the aluminium content, these coatings are either single phase or consist of two phases: NiAljCoAI precipitates in a Ni-Cr matrix. The oxidation and hot corrosion properties of these coatings depend upon the phase distribution and the distribution of the rare earth element yttrium. 3,4 These coatings are formed by electron beam evaporation and, more recently, by low pressure plasma spraying.Plasma spraying is a well established technique of forming metallic and ceramic coatings to protect the surface of engineering components against corrosion, erosion, and wear. 5 In this process the powders forming the coating are melted in the plasma flame and are projected at high velocities on the substrate to be coated. The molten droplets are flattened on impact and solidify, transferring their heat to the relatively cold « 200°C) substrate. The spraying process gives rise to porosity of "" 2-10%.6 Even though the plasma is generated in a flowing gas mixture of Ar, He, N 2' and H 2 , the spraying itself is normally carried out in air, giving rise to oxidation of the metallic coatings. Air sprayed coatings cannot thus meet the quality requirements of coatings for turbine blades and vanes. This deficiency was overcome by developing the low pressure plasma spraying process, in which investigated by melting plasma sprayed NiCoCr AIY coatings on a Nimonic 75 substrate. This work focuses mainly on the effect of various laser processing parameters on the structure of remelted layers. Preliminary data on the hot corrosion properties of the laser melted coatings are also presented.

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Section: Mcraiymentioning

confidence: 99%