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为提高Nb-1Zr合金基体在600℃大气环境下的抗氧化性能,采用等离子增强电弧离子镀技术在Nb-1Zr合金表面低于300℃下实现不同复合结构的NiCr涂层。利用恒温氧化表征了涂层在600℃、500 h大气环境下的抗氧化性能,揭示了不同复合结构涂层失效以及抗氧化机理。结果表明,单一NiCr涂层中存在的大量“微孔”结构缺陷相互连通构成了氧元素进入基体的扩散通道,界面处基体首先发生氧化,生成以Nb_2O_5为主的粉末状氧化产物。随着氧化时间的延长,氧化产物逐渐增多,体积逐渐膨胀,造成表面鼓泡直至破裂失效。采用NiCr多层复合结构能够显著降低涂层中形成“贯穿孔”的几率,但并未改变涂层的失效方式。而基体与NiCr层之间引入Cr过渡层,能够在界面处与扩散进入的氧首先反应生成致密的Cr_2O_3层,阻碍氧向基体的进一步扩散,且随着氧化时间的延长,涂层中的Cr向表面的扩散使得其表面相应形成一层致密的Cr_2O_3层,双层致密氧化膜的形成确保了基体抗氧化性能的提高。结果显示,Cr/NiCr多层复合结构涂层能够使Nb-1Zr合金在600℃大气环境下的抗氧化时间延长至500 h,氧化增重率仅有0.08g·(m~2·h)~(-1)。
In order to improve the oxidation resistance of Nb-1Zr alloy substrate at 600 ℃, NiCr coatings with different composite structures were fabricated on the surface of Nb-1Zr alloy at below 300 ℃ by plasma-enhanced arc ion plating. The oxidation resistance of the coating was characterized by isothermal oxidation at 600 ℃ for 500 h. The failure mechanism of different composite structures and the anti-oxidation mechanism were revealed. The results show that a large number of “microporous” structural defects in a single NiCr coating are connected to each other to form a diffusion channel for oxygen to enter the matrix. The substrate first oxidizes to form a powdered oxidation product mainly containing Nb 2 O 5. With the extension of oxidation time, the oxidation products gradually increased, the volume gradually expanded, resulting in surface bubbling until rupture failure. The use of NiCr multilayer composite structures significantly reduces the probability of forming “through holes” in the coating, but does not change the way the coating fails. The introduction of Cr transition layer between the substrate and the NiCr layer can react with the diffused oxygen first to form a dense Cr 2 O 3 layer at the interface and hinder the further diffusion of oxygen to the substrate. With the extension of the oxidation time, the Cr The surface diffusion causes the surface to form a dense layer of Cr 2 O 3. The formation of double dense oxide film ensures the improvement of oxidation resistance of the matrix. The results show that the Cr / NiCr multi-layer composite coating can prolong the oxidation resistance of Nb-1Zr alloy to 500 h at 600 ℃, and the oxidation weight gain rate is only 0.08g · (m ~ 2 · h) ~ (-1).