Creek effects on the spallation of an alumina layer from a NiCrA1Y coating

The Influence of Nicraly Coatings Roughness on Oxidation Kinetics During Static Oxidation Test at Temperature 1000ºC And 1100ºC / Wpływ Przygotowania Powierzchni Na Kinetykę Utleniania Warstw Typu Nicraly Pod Wpływem Statycznego Utleniania W Temperaturze 1000ºC I 1100ºC

“…The samples removed from the furnaces after 25 hours, regardless of the test temperature is dominated by strong reflections Ni3Al phase. In the case of staying the sample at 1000ºC can further be noted the presence of oxide phases reflection: NiAl 2 O 4 The thickness of oxide layer in the depression of the roughness profile of the bond-coat at a temperature of 1000ºC…”

“…In the bottom of the roughness profile of the bond-coat there is a close to linear increase in thickness as a function of time scale. These are relatively compact layer, consisting mainly of Al 2 O 3 and small amounts of complex oxide network type of: NiCr 2 O 4 and NiAl 2 O 4 . In the case of oxide layer formed on the tops of the roughness of bond-coat it has a faster growth and greater thickness of the layer.…”

“…This kind of stress generated the microcracks in the peak of bond-coat and in consequence starts of delamination process of TBC system. The value of the stress generated is dependent on the thickness of the TGO zone, TGO zone adhesion to the bond-coat, as well as the radius of profile curvature [4,5]. TBC coatings often kinetics of crack propagation In the ceramic layer is lower than the nucleation of cracks and consequently delamination of the coating are on the top TGO roughness profile.…”

On TGO creep and the initiation of a class of fatigue cracks in thermal barrier coatings

“…The properties presented by Rösler et al [21] and Evans et al [23] appear to correspond to two distinct cases of TGO responses, almost instantaneous relaxation of stresses in Rösler et al [21] versus almost elastic response in Evans et al [23]. In both cases the properties correspond to pure α-alumina (Al 2 O 3 ) [21,23]. As mentioned previ ously, the TGO is composed of α-alumina but it also contains other constituents, such as oxides of zirconium, nickel.…”

“…There is a limited amount of data for TGO properties, in particular at high temperature properties. However, based on work by Evans et al [23] and Rösler et al [21] it is clear that the creep properties differ significantly for the grain sizes observed in the TGO. In addition, French et al [24] …”