Influence of atmospheric plasma spray process parameters on crystal and micro structures of pyrochlore phase in rare earth zirconate thermal barrier coatings. (2019)

• Record Type: Journal Article
• Authors: Pasupuleti, Kirti Teja; Ghosh, Souvik; Dunna, Uma Manikanta; Ramaswamy, Parvati; Narayana Murty, S.V.S.
• Is Part Of: Materials today. Volume 19:Part 2(2019)
• Page Start: 731
• Page End: 736
• Publication Date: 2019
• Subjects: Air plasma spray -- Rare-earth zirconates -- Spray parameters -- XRD -- SEM; Materials science -- Congresses -- Periodicals; 620.1
• DOI: 10.1016/j.matpr.2019.07.760
• Languages: English
• ISSNs: 2214-7853

Abstract

Abstract: Yttria-stabilized zirconia (YSZ) thermal barrier coatings is most widely used in gas turbine engines applications and its primary role is to protect the underlying base metal from degradation at its high temperature (>1000 °C) service environment. While YSZ serves well in this role, materials with higher thermal stability and lower thermal conductivities are required to be developed for attaining higher operating temperatures and thereby higher energy conversion efficiencies. A number of rare-earth zirconates which form the cubic fluorite-derived pyrochlore structures (A2 B2 O7 ) where A: La, Gd, Sm, Ce and B: Zr are being developed, some compositions are more attractive due to their good amalgamation of thermal and mechanical properties. However, when these materials are plasma spray coated on metal substrates, the favorable properties are not immediately realized due to various contributing factors such as poor adhesion/cohesion, microstructure (porosity, defects) or even incomplete stabilization or destabilization of the desired phase (crystal structure) after passing through the plasma. In this paper, plasma sprayable powders of zirconate pyrochlores (or with disordered fluorite structures) synthesized from using La and Ce as the trivalent "A" cation, were plasma sprayed onto Inconel 718 substrates, by using different plasma spray parameters. The considerable influence of these spray parameters on the structural phases (analyzed via XRD) and microstructures (studied via SEM on polished cross section metallographs) are presented in detail.