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| NbSi基合金HRS法制备研究 |
| Preparation of NbSi-based Alloys by HRS Method |
| Received:July 30, 2024 |
| DOI：10.3969/j.issn.1674-6457.2024.10.004 |
| 中文关键词: 铌硅基合金 定向凝固 取向演变 HRS法 选晶法 |
| 英文关键词: NbSi-based alloy directional solidification orientation evolution HRS method grain selection |
| 基金项目:国家自然科学基金(51604173) |
| Author Name | Affiliation | | CAO Bingqian | School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China | | CHEN Senhong | School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China | | QI Chengkang | School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China | | ZENG Long | School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China | | LI Fei | School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China | | XIA Mingxu | School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China | | LI Jianguo | School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China |
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| 中文摘要: |
| 目的 满足高性能航空发动机高压涡轮叶片的制备需求，探索精密铸造方法制备NbSi基高温合金柱状晶和单晶铸件的可行性，并提出面临的主要问题。方法 采用具有螺旋选晶器结构的氧化锆型壳进行了HRS法定向凝固实验，采用扫描电子显微镜观察引晶段纵剖面微观组织，采用EBSD技术测试引晶段纵截面及螺旋段不同高度处横截面的取向信息，分析了螺旋选晶器对铌硅基合金杂晶淘汰的效果及螺旋段的组织取向演变规律。结果 因定向凝固温度较低，致使引晶段、螺旋段组织均为等轴晶组织，且Nbss晶粒与嵌入其中的γ-Nb5Si3晶粒并无普遍严格的取向关系。而螺旋选晶器并未起到取向淘汰作用，这一方面是由于炉膛温度过低(1 720 ℃)不能达到合金液定向凝固的效果所致，但另一方面，对于初生相为γ-Nb5Si3(小平面相)的过共晶铌硅基合金，因小平面相生长具有强烈的各向异性和较弱的横向扩展能力，因此选晶器不能起到较好的取向淘汰作用。而进一步提高炉膛温度至1 780 ℃，其余参数一致，浇注后型壳软化破裂，合金液漏出。结论 目前，工业制备铌硅基合金定向凝固柱状晶乃至单晶零部件急需解决的是型壳材质耐温能力不足的问题，需开发一种能长时间(30 min以上)承受1 800 ℃以上温度的型壳。选晶法对过共晶铌硅基合金不能起到较好的取向淘汰作用，建议选用籽晶法。 |
| 英文摘要: |
| This work aims to explore the feasibility of preparing NbSi-based superalloy columnar crystal and even single crystal casting and propose the main problems at present to meet the high pressure turbine blade preparation requirements of high performance aero engines. Directional solidification experiments were carried out according to the HRS method using a zirconia mold shell with a spiral selector structure. The longitudinal microstructure of the starter block was observed with a scanning electron microscopy, and the orientation information of the cross section at different heights of the spiral part was tested with the EBSD technology. The effect of spiral crystal selector on the removal of NbSi-based alloy particles and the evolution of microstructure orientation of spiral part were analyzed. Due to the lower directional solidification temperature, both the starter block and spiral part exhibited equiaxed grain microstructures, and there was no generally strict orientation relationship between Nbss grains and embedded γ-Nb5Si3 grains. The grain selector did not achieve its intended orientation elimination effect. On one hand, this was due to the furnace temperature being too low (1 720 ℃) to achieve directional solidification of the melt. On the other hand, for hypereutectic NbSi-based alloys with primary γ-Nb5Si3, which had strong anisotropy in growth and weak lateral expansion ability, the selector could not achieve effective orientation elimination. Further increasing the furnace temperature to 1 780 ℃, with other parameters unchanged, resulted in the mold shell softened and cracked after pouring, with the melt leaking out. Currently, the industrial preparation of NbSi-based alloy components with columnar crystals and even single crystal urgently needs to address the issue of insufficient temperature resistance of mold shell materials. It is necessary to develop a type of mold shell that can withstand temperatures above 1 800 ℃ for prolonged periods (over 30 min). And the grain selector does not achieve effective orientation elimination for hypereutectic NbSi-based alloys, so the seeding method is recommended. |
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