Some effects of structure and composition on the properties of electron beam vapor-deposited coatings for gas turbine superalloys II. The origin of defects

Grossklaus, W.; Ulion, N. E.; Beale, H.A.

doi:10.1016/0040-6090(77)90128-6

Cited by 13 publications

(7 citation statements)

References 6 publications

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“…According to Table 2, the spit contained more than 10wt-% of Y while the Cr content was below 4wt-%. High content of Y within the spit volume was reported earlier [6,7]. An EDS spot analysis of the bright precipitates revealed that they contained Ni and Y with an atomic ratio of about 5, as in the Ni 5 Y phase, while the composition of the dark grey background corresponded to that of β-NiAl.…”

Section: Resultssupporting

confidence: 67%

“…The spitting phenomenon is not specific to MCrAlYtype alloys and was also observed during evaporation of 99.999wt-% pure noble metals [8]. A number of possible factors were claimed to be responsible such as instability of the electron beam (EB) power, release of gases entrapped in the pores, volatilisation of nonmetallic inclusions and others [6][7][8]. The only mitigating approach known so far is lowering the EB specific power at the expense of coating deposition rate [8,9].…”

Section: Introductionmentioning

confidence: 99%

“…One of the key phenomena affecting the quality of EB-PVD MCrAlY coatings is spitting, which is manifested as an uncontrolled ejection of liquid droplets from the molten pool followed by their incorporation into the coating in the form of lenticular defects – spits [6,7]. The composition of the spits was found to differ from that of the coating thereby compromising protective properties of the coating.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of spitting behaviour of NiCoCrAlY type materials during electron beam evaporation

Pankov

Seo

Lee

et al. 2020

Materials Science and Technology

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Spitting behaviour of four casted and powder metallurgy ingots used in the fabrication of NiCoCrAlY-type environmental protective coatings by electron beam physical vapour deposition was investigated and correlated with ingot microstructures and compositions. Spits found in the coatings mainly consisted of the Ni5Y phase precipitated in the β-NiAl matrix while their typical size exceeded 50 µm. Spitting was less pronounced for ingots having a higher Cr content, larger size of γ-Ni(Co, Cr) precipitates formed within β-NiAl grains and narrower transitional zone formed at the interface between molten and unmolten ingot regions and consisting of coarsened β grains. Large (above 100 µm) agglomerates of the Ni5Y phase detected below the zone were identified as the main spit precursors.

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Section: Resultssupporting

confidence: 67%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Investigation of spitting behaviour of NiCoCrAlY type materials during electron beam evaporation

Pankov

Seo

Lee

et al. 2020

Materials Science and Technology

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“…It has been shown that rotated, as-deposited structures, in addition to having the typical column-oriented grain structure of PVD deposits, have poorly bonded grain boundaries. 25,26 The structure is in effect a mechanically attached bundle of columnar grains. These structures are the result of shadowing from the point source, and are not found on most PVD coated, rotated substrates.…”

Section: Use Of Rotated Substratementioning

confidence: 99%

Physical vapour deposition processes

Boone¹

1986

Materials Science and Technology

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Physical vapour deposition (PVD) is the process whereby metals and alloys may be transferred in the vapour state from one source to another. It was known as early as 1857, and since 1912 has been operated in vacuum form, both experimentally and commercially, for applying coatings and fabricating bulk shapes. Over the years the basic PVD process has been modified and used in a number of different ways, and these have been given different names. The development of this sometimes conflicting and confusing nomenclature is reviewed as an introduction to a discussion of the background and present status of the PVD process for depositing overlay protective coatings on gas turbine components, a process which has been in use commercially for over 15 years. The requirements for this application are very different from those for most other uses, and these are discussed in terms of their effects on the adherence, structure, and post-coating processing of the applied coatings. The limitations of the process, such as required compositional ranges, growth defect tolerance, line-of-sight deposition, low-angle coatings, and the ability to deposit elements having widely different vapour pressures, are considered. The latest forms of the PVD process are discussed in terms of how these limitations affect them. The present status of PVD processes is examined in the light of the current economic climate and future technological developments. MSTj283 IntroductionIn the early 1960s the development of gas turbine design and materials resulted in a requirement for aerofoil protective coating systems beyond the capabilities of the diffusion applied aluminide coatings then in use. 1 In these systems approximately 70% of the coating was substrate, and increasing the strength of the substrate often reduced the lifetimes of coating systems made from materials that would have lasted longer at higher temperatures. 2 From this new requirement the concept of an overlay coating system was born, and with it a search for a suitable method of deposition.One. process then receiving considerable attention for other applications, physical vapour deposition (PVD), came to be considered for the application of a coating composition developed separately and formed independently of the substrate.Although neither PVD nor the gas turbine were new technologies, the performance requirements that arose in the early 1960s brought them together, and a m'odified coating processing technology emerged. The use of the PVD process for coating gas turbine components presented a set of requirements and problems not normally found with other PVD applications.In this paper, discussion is limited to a metal vapour produced by electron beam evaporation (EB-PVD). However, many of the considerations are also relevant to sputtering or other vapour processes. Within the limits of this paper it is neither possible nor desirable to cover the number of detailed reviews 3 -5 and the immense literature in this area. Instead, following a short historical summary, an attempt is made to e...

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“…The metallurgical characteristics of PVD coatings, specifically MCrA1Y compositions, are also well documented. Boone (1980), Feuerstein et al (1986), and Grossklaus et al (1977) have provided substantial fundamental understanding of MCrAlY coating structure, process related defects pertinent to overlay coating structure, and role of individual elements in MCrA1Y coating structure and properties. Finally, Bianchi (1980) and Bianchi et al (1981) have reported on the service experience of PVD MCrA1Y coatings in aircraft, marine, and industrial gas turbine applications.…”

Section: Introductionmentioning

confidence: 99%

Restoration of Thinned Airfoils by Application of Physical Vapor Deposition Coating

Rose¹,

Price²,

Saenz³

et al. 1993

Volume 3A: General

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The GTCP331-200/250 auxiliary power unit (APU) is used to provide electrical power and compressed air for commercial aircraft, including the Boeing 757 and 767, and Airbus A310. The turbine section of this engine is a three stage axial flow configuration. Due to the combined effect of oxidation and erosion, the useful life of the first stage turbine blade may be limited by loss of material on the airfoil. The effect of material loss is reduction of the airfoil thickness and chord length.This paper discusses a repair that restores the airfoil dimensions by buildup with a physical vapor deposition coating. The repair process includes incoming dimensional inspection of the airfoil, physical vapor deposition with tapered thickness to restore airfoil dimensions, and post deposition processing. The evaluation includes airfoil dimensional inspection, metallographic verification of coating integrity, and finite element modeling to illustrate the effect of material buildup on different locations of the airfoil.

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Some effects of structure and composition on the properties of electron beam vapor-deposited coatings for gas turbine superalloys II. The origin of defects

Cited by 13 publications

References 6 publications

Investigation of spitting behaviour of NiCoCrAlY type materials during electron beam evaporation

Investigation of spitting behaviour of NiCoCrAlY type materials during electron beam evaporation

Physical vapour deposition processes

Restoration of Thinned Airfoils by Application of Physical Vapor Deposition Coating

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