抽拉速率对DD5合金大尺寸单晶叶片定向凝固组织演变的影响

Effects of Withdrawal Rate on Solidification Microstructures of Large Size Single Crystal Blade of DD5 Superalloy

研究了高速定向凝固条件下抽拉速率对F级燃气轮机用DD5合金大尺寸单晶叶片凝固组织的影响。结果表明:一次枝晶间距随抽拉速率的增加而减小;凝固位置越高,一次枝晶间距越大。在相同高度位置,元素偏析程度随抽拉速率增加呈增大的趋势;γ′相平均尺寸随抽拉速率增大而减小。在相同抽拉速率下,凝固位置越高,γ′相平均尺寸越大;碳化物和γ/γ′共晶平均尺寸随抽拉速率增加呈减小趋势;γ/γ′共晶含量、碳化物含量随抽拉速率增大而增加。进一步分析了抽拉速率及凝固高度位置对微观组织及元素偏析的影响机制。

The effect of withdrawal rates on the solidification microstructures of large-size single crystal blades of the DD5 alloy for F class gas turbine was studied under high speed directional solidification condition.The results showed that the primary dendrite spacing decreased with the increase of the withdrawal rate.The primary dendrite spacing increased with the rise of the solidification location.The degree of element segregation increased with the increase of the withdrawal rate at the same height.The average size ofγ’phase decreased with the increase of the withdrawal rate.At the same withdrawal rate,the average size ofγ’phase increased with the increase of solidification position.The average size of carbide andγ/γ’eutectic decreased with the increase of the withdrawal rate.Theγ/γ’eutectic content and the carbide content both increased with the increase of the withdrawal rate.The mechanism of the effect of the withdrawal rate and the solidification location on microstructures and microsegregation was discussed.