Mo含量对第四代单晶高温合金组织及稳定性的影响

为优化第四代单晶高温合金的Mo含量,在真空定向凝固炉中采用选晶法制备1%Mo和3%Mo的2种单晶高温合金,采用JMatPro软件计算了不同Mo含量合金相图,通过扫描电镜和能谱仪研究Mo含量对合金凝固特征,铸态组织,热处理组织和1 100℃/1 000 h长期时效组织的影响.结果表明,随着Mo含量增加,固液相线下移,糊状区变宽,γ相和TCP相含量增加;铸态合金中共晶含量减少,γ′相尺寸减小,其均匀化和立方化程度稍有增加;此外,热处理组织中γ′相立方化程度增加,长期时效组织中TCP相析出量增加,合金的组织稳定性下降.

Influence of Mo content on microstructure and stability of the fourth-generation single crystal superalloys

Two single crystal superalloys with 1 % Mo and 3 % Mo were prepared by vacuum directional solidification furnace to optimize the Mo content of the fourth-generation single crystal superalloy. Phase diagrams of the alloys with different Mo contents were calculated by JMatPro software. The effects of Mo contents on the solidification characteristics, as-cast microstructure, heat treatment microstructure and long-term aging microstructure at 1 100 ℃/1 000 h were investigated by SEM and EDS. The results show that with the increase of Mo content, the solidus and liquidus temperature decreases, the mushy zone becomes wider, and the volume fraction of γ phase and TCP phase increase. The volume fraction of γ-γ′eutectic decreases, and the size of γ′ phase decreases slightly and their homogenization and regularity have been improved. Moreover, when the cubic shape of γ′ phase becomes more regular in the heat treatment microstructure, the volume fraction of TCP phase significantly increases and the microstructure stability decreases.