超瞬态凝固增材制造梯度整体涡轮叶盘用高温合金粉末特性研究:盘体用合金粉末

Characteristics of Ni-Based Superalloy Powders Used for Gradient Integral Turbine Blisk by Ultra-Transient Solidified Additive Manufacturing:Alloy Powders for Disk

针对超瞬态凝固增材制造梯度整体涡轮叶盘用高温合金粉末特性开展研究。根据合金的承温能力和JMatPro相平衡计算结果,分别选用GH4169和K418合金作为盘体心部和轮盘边缘部位材料,DZ4125合金作为叶片材料。采用真空感应熔炼氩气雾化制粉(VIGA)制备高温合金粉末,机械筛分至53~105μm粒度范围,采用差示扫描量热仪(DSC)、场发射扫描电镜(FESEM)、电子探针(EPMA)、激光粒度仪、动态图像粒度粒形分析仪以及综合粉体性能测试仪对高温合金粉末的相变温度、显微组织、元素偏析行为、粒度、粒形、松装密度、振实密度和流动性进行了系统表征。结果表明:K418合金固液温度范围比GH4169合金窄,K418合金的γ′和MC碳化物的开始析出温度均比GH4169高,过渡区(GH4169+K418)混合成分合金主要强化相的析出温度介于GH4169和K418这2种合金之间。GH4169和K418合金粉末形貌主要为球形和近球形。表面和截面显微组织主要呈树枝晶结构,所含元素中偏析倾向较强的元素有Ti、Nb、Zr和Mo,均富集分布于枝晶间,而偏析倾向弱的元素包括Ni、Cr、Fe和Al。高温合金粉末元素偏析类型与铸造镍基高温合金相近,但粉末组织更为细小均匀。激光衍射和动态图像分析法测得的粉末粒度值接近,GH4169的D_(50)分别为79.1和76.2μm,K418的D_(50)分别为67.8和65.6μm。动态图像法测得2种合金均具有较好的球形度,GH4169和K418的SPHT均值分别为0.91和0.90。GH4169和K418合金粉末具有相近的松装密度、振实密度和流动性,其松装和振实密度分别达到合金理论密度的50%和60%,压缩度在13.3%~15.5%范围,粉末具有较好的流动性(18.5~20.4 s·(50 g)^(-1))。

The characteristics of superalloy powders used for the gradient integral turbine blisk by the ultra-transient solidified additive manufacturing were investigated.According to the temperature capacity of the alloy and the phase equilibrium diagram calculated by JMatPro,GH4169 and K418 alloys were selected as the disk hub and rim materials,respectively,whereas DZ4125 was selected as the blade material for integral turbine blisk.The superalloy powder were prepared by vacuum induction melting and argon gas atomization(VIGA)and sieved to the particle size range of 53~105μm.The differential scanning calorimeter(DSC),field emission scanning electron microscope(FESEM),electron probe X-ray micro-analyzer(EPMA),laser diffraction particle size analyzer,dynamic image analysis system and comprehensive powder property analyzer were used to systematically characterize the phase change temperatures,microstructure,element segregation,particle size and shape,apparent density,tap density and flowability of the selected superalloy powders.The results show that the liquidus and solidus temperature range of K418 alloy is smaller than that of the GH4169 alloy.The onset precipitated temperature ofγ′and MC carbides of K418 alloy is higher than that of GH4169.The precipitation temperatures of the main strengthening phases of the(GH4169+K418)hybrid composition alloy in the transition zone are between the GH4169 and K418 alloys.The morphologies of GH4169 and K418 alloy powders are mainly spherical and nearly spherical.The surface and cross-section microstructures are mainly dendritic structure.For the selected alloy powders,the elements Ti,Nb,Zr and Mo,rich in the interdendritic region,exhibit strong segregation tendency,while the elements with weak segregation tendency include Ni,Cr,Fe and Al.The element segregation type of superalloy powder is similar to the cast Ni-based superalloys,however the powders possess finer and more uniform microstructure than the cast superalloy.The particle size distribution of powders measured by laser diffraction and dynamic image analysis methods are similar.The D_(50) value of GH4169 is 79.1 and 76.2μm,and the D_(50) of K418 is 67.8 and 65.6μm,respectively.The dynamic image analysis result shows that the two alloys both possess good sphericity,and the SPHT mean values of GH4169 and K418 are 0.91 and 0.90,respectively.The GH4169 and K418 superalloy powders have similar apparent density,tap density and flowability.In addition,the apparent density and tap density of the two alloy powders can reach 50%and 60%of the theoretical density of the alloy,respectively.Furthermore,the GH4169 and K418 superalloy powders both have good compressibility of 13.3%~15.5%and flowability of 18.5~20.4 s·(50 g)^(-1).