Microstructure evolution and oxidation behavior of in-situ oxide-dispersion-strengthened AlCoCrFeNi2.1 composite coatings manufactured by high-speed laser cladding

Abstract

To develop thermal barrier coatings (TBCs) that protect against high-temperature oxidation, it is critical to explore and develop new bonded coating materials and fabrication techniques. Here, oxide-dispersion-strengthened (ODS) AlCoCrFeNi_2.1 composite coatings were formed using high-speed laser cladding (HSLC), of which long-term oxidation behavior at 1000, 1100, and 1200°C was studied. The results showed that the ODS AlCoCrFeNi_2.1 composite coatings exhibited better oxidation resistance than the conventional NiCoCrAlY coatings and some other high-entropy alloy (HEA) coatings at 1000 and 1100°C. This was because Y₂Hf₂O₇ nanoparticles decreased the thermally-grown oxide (TGO) growth rate and thermal expansion mismatch stresses, and increased the coating/TGO interfacial toughness. The composite coating rapidly failed after only 200 h of oxidation at 1200°C, primarily due to the formation of coarse Al₂Y₄O₉ oxide aggregates within the TGO, which caused the rapid transport of Fe, Cr, Hf, Y, Al, and O atoms. Moreover, the formation of Y₂Hf₂O₇ nanoparticles within the composite coating was induced by regulating the Marangoni convection intensity in the melt pool during HSLC. This report provides a candidate for the next-generation, low-cost, oxidation-resistant bonded coatings.