细化剂与冷却方式对K438合金组织和高温性能的影响  

Effects of inoculation and cooling method on microstructure and high-temperature performance of K438 superalloy

作　　者：郑行 杨伟[2] 雷四雄 张丽攀 ZHENG Hang;YANG Wei;LEI Si-xiong;ZHANG Li-pan(AECC South Industry Co Ltd,Zhuzhou 412002,China;School of Aeronautical Manufacturing Engineering,Nanchang Hangkong University,Nanchang 330063,China)

机构地区：[1]中国航发南方工业有限公司,湖南株洲412002 [2]南昌航空大学航空制造工程学院,江西南昌330063

出　　处：《材料热处理学报》2020年第4期68-74,共7页Transactions of Materials and Heat Treatment

基　　金：国家自然科学基金(51461032);江西省教育厅资助项目(GJJ180513)。

摘　　要：采用模壳面层细化与风冷/空冷相结合,研究了熔模精铸K438合金凝固组织及沉淀相形成规律,提出了改善合金高温力学性能的途径。结果表明,模壳面层细化为凝固过程提供了有效形核质点,促进凝固组织从柱状晶向等轴晶发生转变,有效地细化了合金的晶粒组织。风冷方式抑制了枝晶熟化和沉淀相粗化,显著降低二次枝晶间距及γ′析出相尺寸。截面等轴晶比例的增加有利于提高合金980℃/150 MPa高温持久性能。枝晶组织的细化及细小沉淀相的形成可以改善合金650℃高温拉伸强度,其中风冷试棒的高温屈服强度和伸长率分别为734 MPa和11%,相比空冷态分别提高了5%和41%。Solidification microstructure and precipitation phase of K438 alloy was studied by combining the surface inoculation of mould shell and blast cooling or air cooling method, and the method to improve the high temperature mechanical properties of the K438 alloy was put forward. The results show that the refinement of the mould shell surface provides an effective nucleation particle for the solidification process, promotes the transformation of the solidification structure from the columnar crystal to the equiaxed crystal, and effectively refines the grain of the alloy. Blast cooling can inhibit dendrite ripening and precipitation phase coarsening, and significantly reduce the secondary dendrite spacing and the size of γ ′ precipitated phase. The increase of equiaxed crystal ratio of cross section is beneficial to improve the high temperature rupture time of the alloy at 980 ℃/150 MPa. The high temperature tensile strength of the alloy can be improved by refining the dendritic structure and the formation of fine precipitated phase. The high temperature yield strength and elongation of the blast-cooled alloy are 734 MPa and 11%, respectively, which are 5% and 41% higher than those of the air-cooled alloy, respectively.

关 键 词：冷却速率 细化剂 高温合金 高温性能 

分 类 号：TG132.3[一般工业技术—材料科学与工程]