For the target of enhancing the high-temperature oxidation resistance of Nb521 alloy,(W,Mo,Ti,Cr)Si2/NbSi2 composite coatings were fabricated with a two-step process involving slurry melting followed by pack siliconizing. This study investigated the effect of burnishing aid Si content on the microstructural characteristics of the coatings,as well as their static oxidation resistance and thermal shock performance at 1350 ℃. The findings indicated that the microstructure of the W-Mo-Ti-Cr alloy layer produced by slurry melting transitioned from dense to loose with increasing Si content,with an optimal Si content of 30％ (mass fraction). After undergoing pack siliconizing,the coatings exhibited further densification and mainly comprised an outer (W,Mo,Ti,Cr)Si2 layer and an inner NbSi2 layer. The static oxidation kinetics of the coatings at 1350 ℃ followed a parabolic law. A dense SiO2 protective scale was formed on the surface after 20 hours of oxidation. Notably,the coatings retained structural integrity after 64 thermal shock cycles between 1350 ℃ and room temperature,with the oxide scale adhering firmly to the substrate,while thermal stress cracks within the coating were effectively filled by SiO2.
关键词
铌钨合金Nb521/复合涂层/高温氧化/热震氧化
Key words
Nb521 alloy/composite coating/high temperature oxidation/thermal shocks
万方数据