Microstructural evaluation of ZrO2–MgO coatings

Khan, A. Nusair; Qureshi, Imran Nazir

doi:10.1016/j.jmatprotec.2008.02.032

Cited by 8 publications

(6 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…It has been thought that the stabilization of the tetragonal phase arises from a combination of the surface energy effect and the constraint of the rigid matrix that opposes the transformation to a less dense monoclinic form 42 . In a previous study, as-sprayed ZrO 2 –24MgO top coat showed a complete non-transformable tetragonal phase up to 750 °C, however, after thermal exposure at 1000 °C for 60 h, the transformation of the tetragonal phase to the monoclinic phase was observed in the XRD patterns 33 . Depending on the high temperature environment, the metastable non-transformable tetragonal can be expected to decompose into the cubic and tetragonal equilibrium phases by diffusion of the CaO and MgO stabilizers.…”

Section: Discussionmentioning

confidence: 79%

“…Therefore, calcia partially stabilizes the zirconia, which helps to reduce phase transformations as the coating passes through critical temperature regions. Furthermore, ZrO 2 –MgO has low thermal conductivity (1.0–1.5 W/mK), fairly comparable to ZrO 2 –Y 2 O 3 which suggests that it has an enormous potential to be used as ceramic top coat material for suitable applications 33 – 35 . The desirability of diminishing surface degradation and disruption in the coating layers is based on phase stability and improved microstructure of the TBCs.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Improving wear resistance of plasma-sprayed calcia and magnesia-stabilized zirconia mixed coating: roles of phase stability and microstructure

Hafez

Akila

Khedr

et al. 2020

Sci Rep

View full text Add to dashboard Cite

The phase stability and microstructure of ZrO2–5CaO and ZrO2–24MgO mixed coating (wt%) by air plasma spraying on 304 stainless steel substrates were investigated. A Ni–5Al (wt%) metallic bond coating was firstly sprayed between the substrate and the ceramic top layer. The results were compared with the individual coatings of ZrO2–5CaO and ZrO2–24MgO for a better understanding of the correlation between their microstructures and mechanical properties. Mixed zirconia coating was found to have a mixture of cubic and tetragonal phases that stabilized under different plasma spray conditions. Microscopic observations and elemental composition analysis of as-sprayed mixed coating showed that modified ceramic-matrix grains had been formed. Microsized ZrO2–5CaO particles were embedded in the matrix grain creating an intragranular microstructure. Results indicated that ceramic-matrix grains provided a diffusion barrier for the growth of oxides induced stress near and onto the bond layer that reduced cracks, thereby overcoming the top delamination of the ceramic coating. Moreover, disparity in wear resistance and microhardness behavior of the coatings was influenced by initial feedstock powder and matrix microstructures. Improvement in the wear resistance of the mixed zirconia coating was attributed to a decrease in oxide content, which resulted in an increase in intersplat cohesive strength.

show abstract

Section: Discussionmentioning

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Improving wear resistance of plasma-sprayed calcia and magnesia-stabilized zirconia mixed coating: roles of phase stability and microstructure

Hafez

Akila

Khedr

et al. 2020

Sci Rep

View full text Add to dashboard Cite

show abstract

“…Their bond-coat oxidation product mainly consists of nickel oxides. 16 In the present study, MSZ TBC with the CoNiCrAlY bond coat can be durable up to 900°C while YSZ TBC still preserves its stability at 1000°C. The most dominant phase is Al 2 O 3 in the TGO layer due to the use of the CoNiCrAlY bond coat.…”

Section: Discussionmentioning

confidence: 47%

“…While YSZ with a fully stable tetragonal phase preserves its stability in a range from room temperature to about 1200°C, MSZ has a partially stable tetragonal phase in a range from room temperature to about 950°C. 12,16 In addittion, at elevated temperatures up to around 1250°C, it will decompose into a monoclinic system and MgO. However, MSZ is cheaper than YSZ.…”

Section: Introductionmentioning

confidence: 99%

Comparison of microstructures and oxidation behaviors of ytria and magnesia stabilized zirconia thermal barrier coatings (TBC)

Döleker¹,

Ozgurluk²,

Özkan³

et al. 2018

Mater. Tehnol.

View full text Add to dashboard Cite

Thermal barrier coatings (TBCs) provide protection to minimize aggressive environmental conditions such as oxidation, corrosion and thermal shocks occurring at high temperatures. In this study, a CoNiCrAlY metallic-bond coat was deposited on an Inconel 718 superalloy substrate with a thickness about 100 μm using the atmospheric-plasma-spray (APS) method. The production of TBCs was accomplished by depositing Y2O3 partially stabilized zirconia (YSZ) and MgO-stabilized zirconia (MSZ) as two different ceramic top-coating materials, having the total thickness of 300 μm. The specimens were subjected to a metallographic investigation before the oxidation tests; their surface roughness, porosity, hardness and microstructural properties were investigated and then compared with the results obtained after the oxidation tests. The TBC systems were subjected to isothermal-oxidation tests at 900°C and 1000°C for (8, 24, 50 and 100) h. After the oxidation tests, XRD, SEM and EDX elemental analyses were carried out and the changes in the thickness and structure of the thermally grown oxide (TGO) layer were investigated. A remarkable change occurred between the top and the bond coat in the TBC systems depending on the increasing time and temperature. The TGO layer thickness showed an increase. At the interface, Al2O3 and other mixed-oxide layers occurred. Before and after the oxidation, XRD analyses showed that YSZ had a tetragonal phase and a bit of a monoclinic phase. The MSZ coating included tetragonal, monoclinic and cubic phases at the end of the oxidation. This phase transformation causes a large volume increase in an MSZ lattice. Due to this volume increase, MSZ coatings suffer more damage than YSZ coatings. Keywords: atmospheric plasma spray, thermal barrier coatings, oxidation, ZrO2-Y2O3, ZrO2-MgO Prevleke kot termi~ne prepreke (TBCs; angl.: Thermal Barrier Coatings) zagotavljajo za{~ito pred agresivnim okoljem in zmanj{ajo oksidacijo, korozijo in termi~ni {ok zaradi obratovanja pri visokih temperaturah. V {tudiji avtorji obravnavajo kovinsko difuzijsko vezano prevleko na osnovi CoNiCrAlY, nane{eno na podlago iz superzlitine Inconel 718 debeline okoli 100 μm, ki je izdelana z metodo atmosferskega plazemskega napr{evanja (APS; angl: Atmospheric Plasma Spray). Dve razli~ni kerami~ni TBCs, celotnih debelin 300 μm, so izdelali z nana{anjem z Y2O3 delno stabiliziranega cirkonijevega oksida ZrO2 (YSZ, angl.: Yttria partially Stabilized Zirconia) in z MgO-stabiliziranega cirkonijevega oksida (MSZ; Magnesia Stabilized Zirconia). Na izdelanih vzorcih so izvedli primerjalne metalografske preiskave, pred in po oksidacijskih testih, in sicer: hrapavost povr{ine, poroznost, trdoto in mikrostrukturne lastnosti. TBC-sistema sta bila izpostavljena testom izotermalne oksidacije pri 900°C in 1000°C za (8, 24, 50 in 100) ur. Po oksidacijskih testih so izvedli XRD, SEM, EDX-elementne analize, kakor tudi ugotovili spremembe debeline in strukture termi~no zrasle oksidne plasti (TGO; angl.: Thermally Grown Oxide). Avtorji so ugotovili znatne ...

show abstract

“…Prowadzone są także badania nad zastosowaniem nowych tlenków stabilizujących tlenek cyrkonu. należy do nich zaliczyć tlenki magnezu [12]. Aktualnie producenci proszków do natryskiwania plazmowego oferują proszki ceramiczne tlenku cyrkonu stabilizowane tlenkiem magnezu i wapnia [13].…”

Section: Wstępunclassified

Mikrostruktura powłokowych barier cieplnych natryskiwanych metodą APS z zastosowaniem nowych proszków ceramicznych

Sosnowy

Dudek

Gancarczyk

et al. 2012

Przegląd Spawalnictwa

View full text Add to dashboard Cite

StreszczenietW artykule przedstawiono wyniki badań mikrostruktury oraz odporności na utlenianie powłokowych barier cieplnych wytworzonych metodą APS. Jako podłoże zastosowano stop Rene 80. międzywarstwę stanowił wieloskładnikowy stop meCrAlY. Zewnętrzną warstwę ceramiczną stanowiły proszki tlenku cyrkonu stabilizowane tlenkami itru, magnezu i wapnia. Proszki te mogą być stosowane zarówno w procesie natryskiwania metodą APS, jak i w warunkach obniżonego ciśnienia -LPPS. Badania przeprowadzono z zastosowaniem mikroskopii świetlnej i elektronowej mikroskopii skaningowej. Wykonane zostały także pomiary porowatości wytworzonej warstwy. Wykazano, że zastosowanie nowych proszków ceramicznych zapewnia możliwość wytworzenia powło-kowych barier cieplnych, jednak ich maksymalna temperatura pracy, poza konwencjonalnym tlenkiem cyrkonu stabilizowanym tlenkiem itru, jest niższa i nie zapewnia ochrony przed utlenianiem powierzchni elementów silnika lotniczego. abstractThe article presents the results of microstructure and oxidation resistance of thermal barrier coatings produced by APS. Rene 80 alloy is used as substrate and meCrAlY alloy as an interlayer. For outer ceramic layer are used zirconium oxide powders stabilized with yttrium, magnesium and calcium oxides. These powders may be used in both the APS spraying method as in conditions of low pressure -LPPS. The study was carried out with the use of light microscopy and scanning electron microscopy. The effective porosity of layer were also measured. It shows that the use of new ceramic powders provides the ability to produce thermal barrier coatings, but their maximum operating temperature, except the conventional zirconium oxide stabilized with yttrium oxide, is lower and does not provide protection against oxidation of the surface of aircraft engine components.

show abstract

Microstructural evaluation of ZrO2–MgO coatings

Cited by 8 publications

References 8 publications

Improving wear resistance of plasma-sprayed calcia and magnesia-stabilized zirconia mixed coating: roles of phase stability and microstructure

Improving wear resistance of plasma-sprayed calcia and magnesia-stabilized zirconia mixed coating: roles of phase stability and microstructure

Comparison of microstructures and oxidation behaviors of ytria and magnesia stabilized zirconia thermal barrier coatings (TBC)

Mikrostruktura powłokowych barier cieplnych natryskiwanych metodą APS z zastosowaniem nowych proszków ceramicznych

Contact Info

Product

Resources

About