重型燃机定向结晶叶片的组织与性能研究

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	重型燃机定向结晶叶片的组织与性能研究
	姜祥伟
学位类型	硕士
导师	楼琅洪
	2012
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	材料工程
关键词	工业燃机叶片热处理持久性能液态金属冷却 Industrial Gas Turbine Blade Heat Treatment Creep Rupture Properties Liquid Metal Cooling
摘要	"与航空发动机涡轮叶片相比，工业用重型燃气轮机叶片具有以下特点：尺寸大，结构形状复杂，叶片不同部位的尺寸存在较大变化。在定向重型燃机叶片制备中，燃机叶片远离定向凝固设备的冷却盘，叶片厚度增加，导致叶片在凝固过程中温度梯度减小，从而引起燃机叶片不同部位的凝固组织存在较大的差异。本文研究了液态金属冷却技术（LMC）制备的DSM11合金重型燃机叶片不同部位的铸态组织，热处理及持久性能。同时，对国内外重型燃机叶片的组织进行对比分析。得到以下主要结论：随着燃机叶片取样位置远离冷却盘，叶片横截面积增大，叶片不同部位的冷却速率逐渐降低，导致叶片铸态组织发生变化，其中包括：一、二次枝晶间距增大，碳化物由块状转变为草书体状，γ/γ'共晶尺寸增加，共晶体积分数变化不大，保持在3.5﹪到4﹪之间，γ′相尺寸增大，η相的析出倾向增大，Co、W、Mo、Al、Ta和Ti等元素的偏析系数变化不大。冷却速率是影响叶片不同部位枝晶间距和γ/γ'共晶尺寸变化的主要因素，而影响γ/γ'共晶含量变化的因素比较复杂，包括冷却速率、逆扩散和枝晶粗化。影响叶片不同部位碳化物形貌、尺寸和体积分数变化的因素主要是冷却速率的变化。 LMC工艺制备DSM11合金燃机叶片的热处理制度制定为1220±10℃(2h)/AC+ 1120℃(2h)/AC+850℃(24h)/AC；提高固溶温度有利于减少残余共晶的体积分数；相同热处理条件下，随着叶片远离冷却盘，残余共晶体积分数增多，γ'相组织趋于一致，η相全部消除。燃机叶片在930℃/280MPa条件下的持久性能随固溶温度的升高有所提升；相同热处理条件下，随着叶片远离冷却盘，980℃/220MPa条件下叶片持久性能呈下降的趋势；与930℃/280MPa条件下的纵向持久性能相比，叶片横向持久寿命和延伸率有所降低。 LMC工艺制备重型燃机叶片与HRS工艺制备商用燃机叶片相比，LMC工艺获得的重型燃机叶片组织更均匀，一次、二次枝晶间距更小，三次枝晶不发达，共晶尺寸小、含量少，缩孔的尺寸和面积分数更小，块状η相的析出倾向减小。热处理组织更加均匀，残余共晶含量更低，η相完全消除。另外，使用后的商用燃机叶片组织出现退化，燃机叶片不同位置的碳化物出现不同程度的分解，γ′相出现不同程度的粗化。 "
其他摘要	"Compared to aero turbine blades, components used in industrial gas turbines (IGTs) have some unique characteristics such as large size, complicated structure and large variations in section thickness. During solidification of the casting, thermal gradient decreases with increasing the distance from the chill plate, which leads to the change of as-cast microstructure. In this paper, microstructure，heat treatment and stress rupture property in a directionally solidified industrial gas turbine blade cast by liquid metal cooling (LMC) process were investigated. Microstructure of the industrial gas turbine blade in this paper was also compared to that of the commercial parts currently in service. The results can be summaried as follows: With increasing in the distance from the chill plate, cooling rate decreases, which leads to change of as-cast microstructure in different positions of the casting as follows: (1) increasing in primary and secondary dendrite arm spacing, (2) carbides morphology changes from blocky type to Chinese-script type and volume fraction of the carbides increases, (3) size of γ/γ' eutectics increases while its volume fraction keeps constant within the range of 3.5﹪ to 4﹪, (4) tendency of precipitation of η increases. Microsegregation coefficient of main elements, such as W, Ti and Al, was not changed. The main factor that affects the size of eutectic, morphology, size and volume fraction of carbides is cooling rate, while there are several possible reasons when considering the evolution of morphology and volume fraction of eutectics including cooling rate, dendrite coarsening and back-diffusion in solid. Full heat treatment is recommended as 1220±10℃(2h)/AC+ 1120℃(2h)/AC+850℃(24h)/AC. The elevated solution temperature is benificial to the decreasing of residual eutectics, and therefore increasing the creep rupture properties at 930℃/280MPa. Compared to the commercial IGT blades processed by HRS, microstructure of the LMC blades is more homogeneous, primary dendrite arm spacing and secondary dendrite arm spacing are refined, and less tertiary dendrite arm is developed. The size and volume fraction of eutectics and shrinkage decreased, and tendency of precipitation of η is restrained. "
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64546
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	姜祥伟. 重型燃机定向结晶叶片的组织与性能研究[D]. 北京. 中国科学院金属研究所,2012.