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ELECTRON-BEAM AND PLASMA OXIDATION-RESISTANT AND THERMAL-BARRIER COATINGS DEPOSITED ON TURBINE BLADES USING CAST AND POWDER Ni(Co)CrAlY(Sі) ALLOYS PRODUCED BY ELECTRON BEAM MELTING
IV. CHEMICAL AND PHASE COMPOSITION AND STRUCTURE OF CoCrAlYSi POWDER ALLOYS AND THEIR USE

I.Grechanyuk 1,
 
N.Grechanyuk 1*,
 
G.Bagliuk 1,
 
V.G. Grechaniuk 2,
 
O.Khomenko 1,
 
O.Dudnik 1,
 
V.I. Gots 1
 

1 I. M. Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine, Omeliana Pritsaka str.,3, Kyiv, 03142, Ukraine
2 Kyiv National University of Construction and Architecture, Vozdukhoflotsky prospect, 31, Kyiv, 03037, Ukraine
eltechnic777@ukr.net

Powder Metallurgy - Kiev: Frantsevich Institute for Problems of Materials Science NASU, 2022, #07/08
http://www.materials.kiev.ua/article/3461

Abstract

New technology for producing powders from the electron-beam CoCrAlYSi alloy is proposed. The method includes step-by-step grinding of the alloy with a press and two-roll vertical unit. The energy consumed to produce this powder is almost seven times lower compared to traditional methods (crushers, mills) and up to 20 times lower compared to spraying methods. The chemical and phase composition and structure of the CoCrAlYSi powder were studied. The use of the proposed grinding method allowed the production of a powder that corresponded to the original alloy in terms of chemical composition and structure. The powder particles have polyhedral shape, close to round, are quite uniform in size, and almost completely preserve the microstructure of the starting CoCrAlYSi alloy. Grinding the alloy leads to a slight increase in the content of some impurities in the powder of 40–100 μm size fraction; in particular, the amount of oxygen increases from 0.05 to 0.08–0.09 wt.% and that of carbon from 0.06 to 0.08–0.1 wt.%. According to the chemical composition and technical characteristics, the powders correspond to technical specifications for the production of powders used for plasma deposition of two-layer thermal barrier metal/ceramic coatings. The outer ceramic topcoat is formed with the participation of yttria-stabilized zirconia of at least 99.5 wt.% purity. The coating thickness is controlled by technical documents and is 135–225 μm for the metal layer and 80–120 μm for the ceramic layer. The developed metal powders are used to form thermal barrier coatings on various types of gas turbine blades. The structure and composition of a two-layer thermal-barrier coating produced by plasma spraying of CoCrAlYSi alloy and ZrO2–Y2O3 ceramic powders were studied.


CHEMICAL AND PHASE COMPOSITIONS, COCRALYSI ALLOY POWDERS, PLASMA THERMAL-BARRIER COATINGS, STRUCTURE

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