Multifunctional 8YSZ/NiCrAlY Composite Thermal Barrier Coatings for Blast Furnace Copper Tuyere: Microstructure, Properties, and Strengthening Mechanisms

To mitigate melting and wear of blast furnace (BF) tuyere, the NiCrAlY/8YSZ composite thermal barrier coatings (TBC) were applied to the copper substrate via atmospheric plasma spraying. The performance of the coatings was thoroughly evaluated, and industrial trials were conducted. Slag and iron erosion tests revealed that the dense microstructure of 8YSZ effectively prevents penetration, whereas porous ZrO 2 allows infiltration, causing severe damage. To address the thermal expansion mismatch between copper substrate and ceramic, coating systems with different structures were designed while maintaining a consistent total thickness. Thermal shock tests demonstrated that the complete three‐layer structure endured 36% more cycles than samples without the intermediate layer and 125% more than those without the bond coat. Additionally, its bonding strength increased by 16.5% and 32.3%, respectively. Furthermore, the wear volume of the TBC was 84.7% lower than that of the pure copper substrate. Industrial trials demonstrated that tuyere equipped with the three‐layer TBC exhibited an average service life 50% longer than ordinary tuyere. The study confirms that the composite coating system, through optimized material selection and structural design, significantly enhances the erosion resistance and stability of BF tuyere under harsh operating conditions, providing an effective solution for protecting critical BF components.