喷射成形粉末高温合金FGH4095M的制备及组织特征

喷射成形是一种近净成形的在粉末冶金气体雾化制粉技术基础上发展起来的快速凝固技术. 本文采用喷射成形技术制备成分优化后的FGH4095M合金, 研究了喷射成形FGH4095M合金沉积坯的致密度、显微组织特征, 特别是研究了喷射成形高温合金组织中特殊形貌的γ’相. 研究表明, 致密度与沉积坯部位有关, 底部致密度最高, 可达99.63%, 热等静压后的致密度可达100%. 喷射成形合金组织以均匀细小的等轴晶为主, 不存在原始颗粒边界; 一次γ’ 相尺寸约为0.6-0.8 μm, 二次γ’相尺寸约为0.1-0.5 μm, 在二次γ’相的间隙中有少量尺寸约为10-20 nm的三次γ’相. 喷射成形FGH4095M 合金中的二次 γ’相中出现特殊形貌的γ’相, 这是由单个γ’颗粒分裂形成, 与沉积过程的低冷却速度有关. 分裂过程是γ’颗粒总能量降低的过程, γ’颗粒间的弹性交互作用能起到主导作用. 对分裂γ’相的等效直径进行统计, 得到γ’ 相等效直径超过0.40 μm 后, 会出现分裂趋势. 合金具备优异的拉伸性能, 室温塑性得到显著提高, 出现γ’ 相分裂的特殊形貌组织是否对合金性能的提高产生直接影响仍需进行进一步的研究.     

氮气喷射成形FGH4095的组织特征

以氮气为雾化气体采用喷射成形工艺制备了FGH4095高温合金沉积坯, 记录了沉积过程坯体表面温度曲线, 并采用定量金相法、排水法测试了坯体致密度, 观察了坯体晶粒及γ'相的形貌. 结果表明采用氮气作为雾化介质进行喷射成型喷射沉积坯基体致密度可达99%以上, 但也存在着较大的(1—2μm)的气孔, 经热等静压和近等温锻后宏观气孔闭合, 氮以尺寸不超过1 μm的碳氮化物形式存在. 喷射沉积坯以等轴晶组织为主, 坯体内部平均晶粒尺寸约为20—40 μm, 近表面区域晶粒较细, 约为13 μm; 一次γ' 相多数呈尺寸约0.3—0.5 μm不规则块状形貌. 喷射成形坯组织结构的形成与喷射成形过程的降温过程有密切关系.     

Innovative technologies for powder metallurgy-based disk superalloys: Progress and proposal

Powder metallurgy(PM) superalloys are an important class of high temperature structural materials, key to the rotating components of aero engines. In the purview of the present challenges associated with PM superalloys, two novel approaches namely, powder preparation and the innovative spray-forming technique(for making turbine disk) are proposed and studied.Subsequently, advanced technologies like electrode-induction-melting gas atomization(EIGA), and spark-plasma discharge spheroidization(SPDS) are introduced, for ceramic-free superalloy powders. Presently, new processing routes are sought after for preparing finer and cleaner raw powders for disk superalloys. The progress of research in spray-formed PM superalloys is first summarized in detail. The spray-formed superalloy disks specifically exhibit excellent mechanical properties. This paper reviews the recent progress in innovative technologies for PM superalloys, with an emphasis on new ideas and approaches, central to the innovation driving techniques like powder processing and spray forming.     

Effect of helium implantation on SiC and graphite

Effects of helium implantation on silicon carbide(SiC) and graphite were studied to reveal the possibility of SiC replacing graphite as plasma facing materials. Pressureless sintered SiC and graphite SMF-800 were implanted with He+ions of 20 ke V and 100 ke V at different temperatures and different fluences. The He+irradiation induced microstructure changes were studied by field-emission scanning electron microscopy(FESEM), atomic force microscopy(AFM), and transmission electron microscopy(TEM).     

电极感应熔化气雾化制粉技术中非限制式喷嘴雾化过程模拟

电极感应熔化气雾化(electrode induction melting gas atomization, EIGA)是一种制备超洁净无夹杂物的先进制粉技术,本文以粉末高温合金的氩气雾化过程为研究示例,对现有用于实际生产的国内某厂家提供的EIGA用非限制式喷嘴进行建模,采用商用计算流体力学软件FLUENT,分布采用欧拉-欧拉VOF(volume of fluid)多相流方法与欧拉-拉格朗日DPM (discrete phase model)离散相方法,对非限制式环缝喷嘴主雾化与二次雾化过程进行了数值模拟.通过对主雾化过程中多相流大涡模拟速度流场,主雾化过程中不同阶段高温熔体云图模拟以及二次雾化过程中TAB (Taylor analogy breakup)模型速度流场及TAB模型粒度分布的模拟研究,实现了对EIGA制粉技术中非限制式喷嘴雾化过程的全过程模拟,并预测了雾化后的粉末粒度分布.在此基础上,采用本文模拟使用的非限制式环缝喷嘴,设定与模拟条件一致(进气压力4 MPa,液流直径约4 mm)的实验条件,制备的粉末大部分颗粒的直径大小在100μm左右,该实验结果与模拟得到的粉末直径D50=100μm大小一致,进一步验证了模拟数据的合理性.该方法也适用于非限制式喷嘴里,其他金属或合金的雾化过的模拟研究.     

低温燃烧合成超细陶瓷微粉的最新研究

以硝酸盐-有机燃料混合物体系和硝酸盐-柠檬酸溶胶-凝胶体系为研究对象,综述了低温燃烧合成(LCS)陶瓷粉体的研究进展,介绍了低温燃烧合成陶瓷微粉的原理、方法以及影响因素,并对工艺要求和特点以及实际应用进行了较详尽的介绍.探讨了国内外研究现状、应用前景和发展趋势.     

非金属改性可见光诱导的TiO2光催化

为拓展二氧化钛的光响应波长范围并提高其光催化活性,通常采用掺杂金属、金属氧化物或金属离子的方法。大量研究表明,掺杂金属、金属氧化物或金属离子往往以损失TiO2光催化剂在紫外光区的光催化活性为代价,而掺杂非金属离子不但能将TiO2的光响应波长拓展至可见光区域外,还能保持在紫外光区的光催化活性,在利用太阳光光催化方面展现出崭新的应用前景。本文综述了非金属氮、碳、硫、氟等掺杂改性二氧化钛光催化的最新进展。     

Energy conversion materials for the space solar power station

Since it was first proposed, the space solar power station(SSPS) has attracted great attention all over the world; it is a huge space system and provides energy for Earth. Although several schemes and abundant studies on the SSPS have been proposed and conducted, it is still not realized. The reason why SSPS is still an idea is not only because it is a giant and complex project, but also due to the requirement for various excellent space materials. Among the diverse required materials, we believ...     

等离子体与石墨及其涂层相互作用的研究

应用ＬＡＳ－２０００辐照设备、射频离子源设备及ＨＬ－１Ｍ装置对等离子体与石墨及其涂层的相互作用进行了系统研究,为进一步优化ＨＬ－１Ｍ装置原位处理工艺、杂质控制以及ＨＬ－２Ａ装置第一壁的选材和第一壁处理、杂质控制等提供依据。     

Oxidation during the production of FGH4095 superalloy powders by electrode induction-melt inert gas atomization

Super-clean and super-spherical FGH4095 superalloy powder is produced by the ceramic-free electrode inductionmelt inert gas atomization(EIGA) technique.A continuous and steady-state liquid metal flow is achieved at high-frequency(350 k Hz) alternating current and high electric power(100 k W).The superalloy is immersed in a high-frequency induction coil,and the liquid metal falling into a supersonic nozzle is atomized by an Ar gas of high kinetic gas energy.Numerical calculations are performed to optimize the structure parameters for the nozzle tip.The undesired oxidation reaction of alloying elements starts at 1000?C with the reaction originating from the active sites on the powder surfaces,leading to the formation of oxides,Me_xO_y.The role of active sites and kinetic factors associated with the diffusion of oxygen present in the atomization gas streams are also examined.The observed results reveal that the oxidation process occurring at the surface of the produced powders gradually moves toward the core,and that there exists a clear interface between the product layer and the reactant.The present study lays a theoretical foundation for controlling the oxidation of nickel-based superalloy powders from the powder process step.