h-BN/ZrO2复合材料的制备与抗钢液侵蚀机制研究

Study on the Preparation and Anti-Steel Liquid Erosion Mechanism of h-BN/ZrO2 Composite Materials

摘要:

h-BN/ZrO₂（六方氮化硼/氧化锆）复合材料因综合性能优异，是一种具有应用前景的高温材料，尤其是在薄带连铸连轧工艺中作为一种优异的侧封材料具有独特的优势。然而，作为侧封板的BN-ZrO₂复合陶瓷在服役过程中经常因被钢水腐蚀而失效。因此，提高h-BN/ZrO₂复合材料的耐磨性、耐腐蚀性、抗热震性具有重要现实意义。在常规烧结工艺中，烧结助剂主要是通过提高离子扩散系数、活化表面能，或者形成液相提高传质速率来影响陶瓷材料的性能，进而促进烧结致密化。为了提高BN/ZrO₂复合陶瓷的力学性能和耐腐蚀性能，采用放电等离子烧结（SPS）工艺，通过加入不同的烧结助剂，制备出不同h-BN/ZrO₂复合材料。通过对比不同h-BN/ZrO₂复合材料抗钢液侵蚀过程，研究了氧化锆（ZrO₂）晶型和含量及添加剂种类对复合材料微观结构和物理性能的影响，分析了烧结助剂对SPS烧结过程的作用机理。同时，还研究了不同h-BN/ZrO₂复合材料对钢水的耐腐蚀性。结果表明，ZrO₂的耐腐蚀性能远高于BN（氮化硼）。对不含添加剂的h-BN/ZrO₂复合材料，侵蚀80 min后，其侵蚀层厚度明显增大，达到40 μm左右，且侵蚀层与基体层之间没有过渡层。说明，h-BN/ZrO₂复合材料的侵蚀损伤主要是由h-BN的高温氧化挥发造成的，而钢液中分布的B和N元素是由BN氧化分解引起的，而钢液中的氧起着关键性的作用。SiO₂和La₂O₃作为添加剂时，试样存在明显的过渡层，钢液较容易进入基体；Al₂O₃和MgO作为添加剂时，侵蚀层和基体之间的过渡层存在明显的孔洞，侵蚀层对钢液的阻碍作用较强。合理调控添加剂，可以形成侵蚀层、过渡层和基体层。通过对不同h-BN-ZrO₂复合陶瓷抗腐蚀性能的研究，明确了不同h-BN-ZrO₂复合陶瓷在钢液中的侵蚀机理，为制备高性能且具有优异抗侵蚀性能的h-BN/ZrO₂复合材料提供了理论借鉴和工艺参考。(专精特新·特殊环境材料服役行为专辑十五之六)

Abstract:

The h-BN/ZrO₂ composite material， known for its excellent overall performance， is a promising high-temperature material， especially as an excellent side-sealing material in the thin strip continuous casting and rolling process. However， the BN-ZrO₂ composite ceramic often fails due to molten steel-induced erosion when used as a side-sealing plate. Therefore， it is of significant practical importance to enhance the wear resistance， corrosion resistance， and thermal shock resistance of h-BN/ZrO₂ composite materials. In conventional sintering processes， sintering additives primarily affect ceramic performance by increasing ionic diffusion coefficients， activating surface energy， or forming liquid phases to improve mass transfer rates， thereby promoting sintering densification. By adding different sintering additives and using the spark plasma sintering （SPS） process， the erosion resistance of different BN/ZrO₂ composite materials against molten steel was compared. The study investigated the effects of zirconia crystal form and content， as well as the types of additives， on the microstructure and physical properties of the composite materials， along with analyzing the mechanisms of action of the sintering additives during the SPS sintering process. Additionally， the corrosion resistance of different BN/ZrO₂ composite materials against molten steel was studied， with the expectation that the SPS process can produce BN composite ceramics with high mechanical properties and corrosion resistance. The results indicate that zirconia exhibits significantly higher corrosion resistance than boron nitride. For the BN/ZrO₂ composite material without additives， the thickness of the eroded layer significantly increased， reaching about 40 μm after 80 min of erosion. There was no transition layer between the eroded layer and the substrate layer， indicating that the erosion damage of the h-BN/ZrO₂ composite material is primarily caused by the high-temperature oxidation and volatilization of h-BN. The distribution of B and N elements in the steel originates from BN oxidative decomposition， with dissolved oxygen playing a key role. Specimens with BSiO₂ and La₂O₃ additives developed an obvious transition layer， and it is easier for the steel to enter into the matrix. Specimens with Al₂O₃ and MgO additives exhibited obvious pores between the erosion layer and the matrix. The erosion layer is a stronger obstacle to the steel. Reasonable regulation of additives can form erosion layer， transition layer and matrix layer. This study clarified the molten steel erosion mechanisms of different BN-ZrO₂ composite ceramics， providing theoretical guidance for the fabricating high-performance h-BN/ZrO₂ composites with excellent erosion resistance.