Phase transformation and bond coat oxidation behavior of plasma-sprayed zirconia thermal barrier coating

Oxidation and crack nucleation/growth in an air-plasma-sprayed thermal barrier coating with NiCrAlY bond coat

“…Energydispersive spectrometer (EDS) analysis revealed that these massive oxides contained 15-45 at.% nickel, 8-24 at.% chromium and 2-30 at.% aluminum, while the Al 2 O 3 layer contained N40 at.% Al, with b2 at.% Cr and b2 at.% Ni. The composition of the massive oxides was similar to that reported by other researchers [24,25].T h e s eo x i d e s appeared to be a mixture of chromia ((Cr,Al) 2 O 3 ), spinels (Ni(Cr,Al) 2 O 4 ) and nickel oxide (NiO) (Fig. 3) layer became thicker, which was~1.1 Am after 100 h; however, the CSN region virtually did not grow as the exposure time increased (Fig.…”

“…The formation of spinel (Ni(Cr,Al) 2 O 4 ) and NiO at the interface between the ceramic coat and Al 2 O 3 layer has been reported by many researchers [11,[22][23][24][25].I th a sb e e n suggested that below 1000 8C, one of the possible causes of spinel formation between the ceramic coat and the Al 2 O 3 layer in an EB-PVD-produced TBC system is transportation of nickel through the Al 2 O 3 layer [3], since thermodynamic considerations indicate that Al 2 O 3 would tend to form first in NiCrAlY bond coats [3,26]. In the present study, (Cr,Al) 2 O 3 d Ni(Cr,Al) 2 O 4 d NiO oxides were observed even after only a 1-h thermal exposure in air at 930 8C (Fig.…”

“…It has been reported that Ni(Cr,Al) 2 O 4 (spinels) and NiO formed at above 1000 8C during the oxidation of thermal barrier coating systems [11,[22][23][24][25]. It was suggested that these two oxides were detrimental to the durability of thermal barrier coating systems, because of the rapid local volume increase [24]. Hence, to gain a better understanding of the TBC failure mechanism, more attention needs to be paid to the detailed oxidation behaviors of the bond coat.…”

Structure, composition, and defect control during plasma spray deposition of ytterbium silicate coatings

“…The air plasma spray (APS) process is an economical and often reliable method for the deposition of such coatings, and has attracted attention for the deposition of EBCs on SiC components [24,25,28,29,[34][35][36][37][38]. This is a logical extension to its already widespread use for the deposition of the thermal barrier coating (TBC) systems used to protect superalloy components in current gas turbine engines [39][40][41][42][43][44]. However, preliminary studies of tri-layer ytterbium monosilicate/mullite/silicon EBCs have shown a significant sensitivity of the coating's steam cycling durability to the composition, structure, and various defects incorporated into the layers during APS deposition [28,29].…”

Thermal stability of atmospheric plasma sprayed (Ni, Cu, Co)–YSZ and Ni–Cu–Co–YSZ anodes cermets for SOFC application

“…In fact, in this kind of cermets elaborating process, when the supplied powders are sprayed, they are firstly melted and then propelled, to reach the substrate with assuming spherical shape during their flight due to the surface tension, but they will be considerably deformed at impingement on the substrate, losing their kinetic and thermal energy and then, will solidify in lamellas forms at a cooling rate of 10 6 K.s -1 [28]. The succession of impacts of powder particles, which are fully or partially melted, creates a superposition of irregular lamellas, leading to a bimodal structure, also known as composite structure, with the coexistence of a porous area and another one in the form of clusters of grains [29][30][31][32]. It can be seen, in Fig.…”