The chemical and mechanical processes of thermal fatigue degradation of an aluminide coating

摘要: The influence of strain history on the oxidation and mechanical degradation an aluminide coating was examined by induction heating stepped-disk specimens. applied to a single-crystal Ni-base superalloy (RENE N4) pack aluminization. anisotropic elasticity substrate allowed simultaneously subjecting different amplitudes. Two distinct modes were observed for tests performed in air between temperature limits 520 °C 1080 °C: scalloping (spatially periodic surface roughening) cracking. degree became more severe as compressive imposed increased. Six thousand cycles peak strains -0.20 0.007 pct produced uniform oxidation, without scalloping, whereas 6000 -0.56 0.01 gave 80 thickness. Cracks along grain boundaries after -0.45 0.16 pct. depth found correlate approximately with strain. Based this correlation, mechanism scallop initiation growth involving cyclic breakdown oxide irreversible creep is proposed. Cracking attributed tensile below transition coating. results obtained from study indicate that important variable which should be included when determining rate coatings alloys.