Dilatometric Study of High Temperature Exposure Effects in Multiphase Fe-Al Intermetallic/Oxide Ceramic Coating Deposited by Gas Detonation Spraying

Intermetallics are known for their unique mechanical and thermal properties, and thus they are used as structural materials to be applied in multilayer protective coatings. A special protective barrier features can be achieved with the gas detonation spraying (GDS) process. The resultant structure contains both intermetallic phases and oxide ceramics. Both thermal and mechanical properties of the GDS coating differs from properties of the intermetallic powder substrate material. However, as was proved in a course of a complex thermophysical property study performed for a certain Fe40Al at.% GDS coating these properties change when the coating material is exposed to temperature exceeding a certain level. In order to characterize temperature induced changes the Fe40Al at.% GDS coating was subjected to systematic dilatometric studies. The measurements were carried out from the room temperature up to 1100 deg. C repeated cycles. The results of measurements performed on the coating material specimens were referred to results of dilatometric measurements done on the same sintered Fe40Al at.% GDS feedstock powder material. The investigations revealed both non-reversible changes and reversible 2-nd order magnetic phase transition in the coating material. The findings contribute to better understanding of the GDS process phenomena.