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

ABSTRACT

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.

KEYWORDS:

• MCrAlY
• NiCoCrAlY
• EB-PVD
• electron beam evaporation
• spitting
• coating

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Sunghun Lee http://orcid.org/0000-0002-2184-3774

Eungsun Byon http://orcid.org/0000-0002-5145-3339

Additional information

Funding

This work was supported by the National Research Council of Canada [Projects No. A1-012438 and No. A1-015303] and the National Research Council of Science and Technology of the Republic of Korea: [International joint research project No. AM-16-001].