Influence of TGO Composition on the Thermal Shock Lifetime of Thermal Barrier Coatings with Cold-sprayed MCrAlY Bond Coat

Abstract

NiCoCrAlTaY bond coat was deposited by cold spraying to assemble thermal barrier coatings (TBCs). The microstructure of the cold-sprayed bond coat was examined using scanning electron microscopy. TBCs consisting of cold-sprayed bond coat and plasma-sprayed YSZ were pretreated at different conditions to form different thermally grown oxides (TGOs) before thermal cycling test. The influence of the TGO composition on the thermal cyclic lifetime was quantitatively examined through the measurement of the coverage ratio of the mixed oxides on the bond coat surface. The results showed that the bond coat exhibited a dense oxidation-free microstructure, and TGOs in different morphologies and constituents were present after thermal cyclic test. The formation of TGOs was significantly influenced by pretreatment conditions. Two kinds of TGO were detected on the surface of bond coat after the spallation of YSZ coatings. One is the a-Al 2 O 3 -based TGO and the other is the mixed oxide. It was found that the thermal cyclic lifetime is inversely proportional to the coverage ratio of the mixed oxides formed at the bond coat/YSZ interface. The high coverage ratio of the mixed oxide on the interface leads to the early spalling of YSZ coating.

Effect of Chemical Compositions and Surface Morphologies of MCrAlY Coating on Its Isothermal Oxidation Behavior

“…Cold spraying is also being investigated to deposit MCrAlY coating (Ref [24][25][26][27]. A cold-sprayed coating is formed through the plastic deformation upon the impact of sprayed particles at a temperature well below the melting point of the spray material, which makes the cold spraying become an alternative method to deposit a dense MCrAlY bond coat in thermal barrier coatings without oxidation (Ref [24][25][26][27][28].…”

Revestimentos para barreira térmica: evolução e perspectivas

“…Em função de tais características, diversas pesquisas têm sido realizadas utilizando estes métodos de aplicação [35][36][37][38]. Os resultados são, em geral, promissores, encontrando aplicação rela em diversos segmentos.…”

“…Como a oxidação da camada de ligação, típica dos TBC's em serviço, afeta especialmente a vida dos revestimentos, causando sua delaminação, diversos estudos vêm sendo atualmente efetuados nesta linha, buscando maior entendimento do processo em si e da variação ocasionada por este processo nas tensões e morfologia da interface [35,[58][59][60][61][62][63][64].…”

Improved Deposition Efficiency of Cold-Sprayed CoNiCrAlY with Pure Ni Coatings and Its High-Temperature Oxidation Behavior after Pre-Treatment in Low Oxygen Partial Pressure

“…It has been reported that Al 2 O 3 exhibits better adhesion to YSZ coatings and a lower growth rate than other oxides, such as NiO, Cr 2 O 3 , and spinel. 4,13) Ni/Cr mixed oxides in TGOs grow rapidly, resulting in high volumetric expansion stress in the YSZ coating, 4,14) which promotes the failure of TBCs. The continuous and uniform alumina-based TGO formed on the cold-sprayed bond coat protects the bond coat from fast oxidation.…”