Cyclic oxidation behavior of glass–ceramic composite coatings on superalloy K38G at 1100 °C

The SiO2–Al2O3–ZrO2–CaO–ZnO glass–ceramic composite coatings (GC), nanocrystalline NiCoCrAlY coating, and their combinations (bi-layer GC/NiCoCrAlY) were prepared on K38G specimens. The thicknesses of the glass–ceramic coatings and the NiCoCrAlY coatings were about 10 μm and 20 μm, respectively. Cyclic oxidation tests were carried out at 1100 °C for 120 cycles. Microstructures of the specimens before and after oxidation tests were characterized by SEM, EDS and XRD. The glass–ceramic coatings with or without a NiCoCrAlY intermediate layer improved the isothermal and cyclic oxidation resistance of the Ni-base superalloy K38G at 1100 °C, and performed better than the NiCoCrAlY coatings. An alumina layer formed at the glass/metal interfaces of the specimens coated by the glass–ceramic coatings with or without a NiCoCrAlY intermediate layer. The NiCoCrAlY intermediate layer was beneficial to the cyclic oxidation resistance of the glass–ceramic coatings.