Abstract
1. Among coatings of NiCrAlY, CoCrAlY, and NiCoCrAlY the thermal fatigue resistance is highest for coatings of the NiCoCrAlY type under conditions of 100⇌950 °, th=1.5 min, Δɛ= 0.6-3.0%. 2. Thermal fatigue fracture of samples with protective coatings is multicentered in character. The type of fracture and crack development depend on the deformation in the cycle and the composition of the coating. 3. In coatings of CoCrAlY and Ni-15Al-35Cr-Y, with the lowest thermal fatigue resistance, all cracks propagate radially and pass into the base metal. The characteristic feature of the NiCoCrAlY coating with a β + γ structure, which has the highest thermal fatigue resistance, is branching of cracks and slow propagation. 4. The reduction in the ductility of the surface layer of the material with a coating leads to a 30–50% drop of the thermal fatigue resistance in air in the range of Δɛ> 0.8–1.0%. When deformation is reduced in the range of N>103(Δɛ < 0.6%) the thermal fatigue resistance is the same for coated and uncoated samples.
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