(1. 長安大學(xué)材料科學(xué)與工程學(xué)院，西安 710064；
2. 西北工業(yè)大學(xué)凝固技術(shù)國家重點實驗室，西安 710072)
摘 要: 沉淀強(qiáng)化鈷基單晶高溫合金具有成本低、初熔點高和抗熱腐蝕性能優(yōu)異等特征，是制備在熱腐蝕環(huán)境下長期服役的單晶渦輪葉片的重要候選材料。本文總結(jié)了沉淀強(qiáng)化鈷基單晶高溫合金的凝固特征溫度、顯微偏析、凝固路徑和枝晶組織等凝固行為，并與典型鎳基單晶高溫合金的凝固行為進(jìn)行了對比。Ta、Ti和Nb元素的添加顯著地降低了固相線溫度和液相線溫度，并擴(kuò)大了結(jié)晶溫度區(qū)間，而Cr、V、Mo和Ni元素對凝固特征溫度的影響較小。凝固時Al、Ta和Ti元素偏析于枝晶間區(qū)域，W元素偏析于枝晶干區(qū)域，Cr和Ni元素的顯微偏析傾向較弱。同時，含Ta/Ti的鈷基單晶高溫合金在凝固末期形成了多種枝晶間析出相，導(dǎo)致合金具有較復(fù)雜的凝固路徑。此外，與鎳基單晶高溫合金類似，定向凝固時冷卻速率和合金成分特征均影響了鈷基單晶高溫合金的一次枝晶間距。
關(guān)鍵字: 鈷基單晶高溫合金；沉淀強(qiáng)化；凝固特征溫度；顯微偏析；凝固路徑；枝晶組織
（1. School of Materials Science and Engineering, Chang''an
University, Xi''an 710064, China;
2. State Key Laboratory of Solidification
Processing, Northwestern Polytechnical University, Xi''an 710072, China）
Abstract:As an important candidate material for the preparation of single crystal turbine blades in long-term service under thermal corrosion environment, the γ'''' strengthened cobalt-based single crystal superalloys occupy the characteristics of low cost, high initial melting point, excellent thermal corrosion resistance, et al. This paper summarized the solidification behaviors of γ'''' strengthened cobalt-based single crystal superalloys, such as the solidification characteristics temperatures, microsegregation behavior of alloying elements, solidification path and dendritic microstructure, and compared with those of typical Ni-based single crystal superalloys. The additions of Ta, Ti and Nb significantly decrease the solidus and liquidus temperatures and expand the solidification range of cobalt-based single crystal superalloys. However, Cr, V, Mo and Ni elements have less effect on the solidification characteristics temperatures. During solidification, Al, Ta and Ti elements segregate to interdendritic region, W element segregates to dendritic core, and the microsegregation degrees of Cr and Ni elements are relatively weak. Due to the severe microsegregation of Ta and Ti elements, various interdendritic precipitations with relatively high Ta/Ti contents form at the last stage of solidification, which complicates the solidification paths of cobalt-based single-crystal superalloys. Finally, similar to Ni-based single crystal superalloys, the as-cast dendritic microstructure of γ'''' strengthened cobalt-based single crystal superalloys is refined with increasing cooling rate and content of high refractory elements.
Key words: γ'' strengthened cobalt-based single crystal superalloy; solidification characteristics temperature; microsegregation behavior; solidification path; dendritic microstructure
