铌合金表面MoSi2-B4C复合涂层的快速烧结制备及高温氧化行为

Rapid sintering and high temperature oxidation behavior of MoSi2-B4C composite coatings on Nb alloy

摘要:

以Mo-Si-B4C混合粉末为涂层原料,采用放电等离子烧结在铌合金表面原位反应烧结制备MoSi2-B4C复合涂层,研究涂层组织形成过程及界面反应特征,考察涂层在1450℃下的抗氧化性能。结果表明,在烧结的升温阶段,MoSi2相就已完全形成,而在保温的初期阶段,部分B4C颗粒又与邻近的MoSi2反应生成了SiC和Mo2B5。烧结过程中,涂层中的Si和B向基体合金扩散,形成了由NbSi2 + NbB外层和Nb5Si3内层组成的互扩散区。涂层在1450℃至少100h内可有效保护基体,表面生成了致密的SiO2-B2O3氧化膜,而互扩散区内NbB的存在有效阻碍了氧化过程涂层中Si的内扩散。

Abstract:

MoSi2-B4C composite coatings were prepared on Nb alloy by spark plasma sintering process. Pure Mo, Si and B4C powders were used as the coating starting materials. The microstructure formation process and interface reaction characteristics of the coatings during SPS were studied. The oxidation resistance of the coatings at 1450℃ was investigated. The results showed that the MoSi2 phase formed completely in the coatings during the heating stage of sintering, and the B4C particles reacted with the neighboring MoSi2 to form SiC and Mo2B5 at the initial stage of holding time. During the sintering process, elements Si and B diffused inwardly from the coatings to the Nb substrate, forming an interdiffusion zone composed of NbSi2+ NbB outer layer and Nb5Si3 inner layer. The coatings could protect Nb alloy effectively from oxidation at 1450℃ for at least 100h, and dense SiO2-B2O3 oxide scales were formed on the surfaces of the coatings. The presence of NbB in the interdiffusion zone effectively impeded the inward diffusion of Si in the coating during the oxidation process.