成分优化对617和740镍基合金铸态组织的影响
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摘要
利用光学显微镜、扫描电镜和电子能谱仪研究了成分优化对617和740两种镍基合金铸态组织的影响。结果表明,经成分优化后617合金的枝晶间距变小,而740合金的枝晶间距变大。这是由于成分过冷导致的冷却速度发生变化所引起的;617成分优化前后主要正偏析元素的偏析指数变化不大,740中易偏析元素Nb、Si偏析明显减轻;617经成分优化后析出相仍为M6C,只是形态上更加弥散细小,且主要沿晶界析出,740经成分改进后G相明显减少,晶界碳化物析出增加;成分调整后导致的过冷度变化以及碳化物析出,使617和740改进型合金的晶粒均明显细化。
Effects of composition optimization on microstructure of as-cast 617 and 740 nickel-based alloys were studied by OM, SEM and EDS. The results show that the dendrite arm spacing decreases for the 617 alloy after composition optimization while that increases for the 740 alloy, due to the change of the cooling rate derived from composition supercooling. The segregation coefficient of main positive segregation elements in 617 alloy has little change, while segregation of Nb and Si reduces in 740 alloys after composition optimization. The precipitated phase of 617 alloy is still M6 C after optimization, the form becomes more dispersed and fine and the carbide precipitates primarily along the grain boundary. While G phase decreases obviously in 740 alloys after optimization and precipitated carbides at the grain boundary increase. The change of supercooling degree and precipitates of carbide derived from the composition optimization refine the grains greatly in both 617 and 740 alloys.
Effects of composition optimization on microstructure of as-cast 617 and 740 nickel-based alloys were studied by OM, SEM and EDS. The results show that the dendrite arm spacing decreases for the 617 alloy after composition optimization while that increases for the 740 alloy, due to the change of the cooling rate derived from composition supercooling. The segregation coefficient of main positive segregation elements in 617 alloy has little change, while segregation of Nb and Si reduces in 740 alloys after composition optimization. The precipitated phase of 617 alloy is still M6 C after optimization, the form becomes more dispersed and fine and the carbide precipitates primarily along the grain boundary. While G phase decreases obviously in 740 alloys after optimization and precipitated carbides at the grain boundary increase. The change of supercooling degree and precipitates of carbide derived from the composition optimization refine the grains greatly in both 617 and 740 alloys.
引文
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[2]赵双群,谢锡善,董建新.700℃超超临界燃煤电站用镍基高温合金Inconel740/740H组织与性能[C]//第九届电站金属材料学术年会论文集(第二卷).成都:2011:278-288.
[3]彭建强.700℃等级超超临界汽轮机用材探讨[J].大型铸锻件,2014(1):1-8,38.
[4]田宇,彭建强,魏双胜,等.我国超超临界汽轮机用高温铸件材料发展趋势[J].大型铸锻件,2016(1):1-5.
[5]傅万堂,张百忠,王宝忠.超临界与超超临界转子材料发展情况综述[J].大型铸锻件,2008(5):33-36,41.
[6]胡汉起.金属凝固原理[M].北京:机械工业出版社,1991.
[7]Caron P.Highγ′solvus new generation nickel-based superalloys for single crystal turbine blade applications[C]//Pollock TM.Superalloys 2000,TMS(The Minarals Metals and Materialssociety),2000:737.
[8]刘喜忠,王晓峰.铝对镍基高温合金凝固行为的影响[J].热加工工艺,2015,44(23):107-108.
[9]曲红霞,寇生中,蒲永亮,等.冷却速率对GH4196合金铸态组织和力学性能的影响[J].铸造技术,2016,37(3):481-484.
[10]Petch N J.The cleavage strength of polycrystals[J].Iron Steel Inst,1953,173(1):25.
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