【作者】 李浩；

【导师】 郭学益；

【作者基本信息】 中南大学 ， 有色金属冶金， 2025， 博士

【摘要】 镍基高温合金具有优异的高温强度和抗腐蚀性能,被广泛应用于航空航天等领域。废弃后的镍基高温合金中富含Re、Mo、W、Ni、Co等多种高价值金属元素,其资源化利用不仅产生较大经济效益,还为我国关键金属资源安全提供保障。但由于镍基高温合金具有组织致密、强度高、耐腐蚀等特点,综合回收过程面临破碎困难、酸耗量大、回收率低等挑战,导致我国目前镍基高温合金回收率较低,大量金属资源未能实现循环利用。针对废旧镍基高温合金资源化利用难的问题,本研究创新性地提出“金属熔体萃取-酸浸-浸出液除杂-氧化焙烧-碱浸/碱熔-萃取”新型技术路线,构建了金属熔体萃取的高温合金回收理论体系,形成了一种高效且原料适应性强的处理方法。该方法可实现Ni、Co、Ta、Mo、W、Re等金属的高效分离与回收,为废旧镍基高温合金的资源化利用提供了坚实的理论基础与技术支撑。论文主要创新点及研究内容如下:（1）本研究提出了“以废治废、协同再生”的新型废旧镍基高温合金资源化利用的方法,即利用废镁合金作为熔体萃取介质与废旧镍基高温合金协同处理实现两种废合金的协同再生。在750℃、镁合金与高温合金质量比为5:1的条件下,镁合金熔体对高温合金中Ni元素表现出显著的选择性溶解行为,Ni提取率最高可达约73%,而Re、W、Mo等高温合金内其他元素则在多孔残留合金（熔体萃取-真空处理后从高温合金内选择性脱Ni后所获得的合金）中实现高效富集。研究揭示了熔体萃取过程中熔体萃取介质优先扩散至高温合金的γ相,并在浓度梯度驱动下进一步向γ/γ′相界面扩散的行为,此时Ta、W、Co、Cr等高熔点难熔元素以离散固态颗粒形式富集,并在随后的真空处理中形成三维多孔骨架结构。熔体萃取过程中镁合金熔体的Al（l）与高温合金内被选择性溶解的Ni（l）形成Ni Al、Ni₂Al₃等金属间化合物,该物质可用于制备具有催化性能的雷尼镍。镁合金添加量对Ni-Al合金的物相组成及雷尼镍的催化性能具有显著影响,过低镁合金添加量将导致Ni Al相含量较高,不利于雷尼镍的制备。利用Ni-Al金属间化合物为前驱体所制备的雷尼镍,在催化1,4-丁炔二醇加氢反应中实现100%的原料转化率和77%的目标产物收率。（2）纯Mg（>99.9 wt%）做熔体萃取介质的废旧高温合金回收及扩大化实验验证:采用纯Mg做熔体萃取介质对废旧高温合金进行熔体萃取处理。研究表明,纯Mg熔体能有效地将高温合金中Ni的含量,由60 wt%降至20 wt%,同时显著降低合金机械强度。该过程中形成的富Ni合金（Ni含量约88 wt%）和富含Re、W、Mo等高价值元素的多孔残留合金,可作为后续金属资源回收的重要原料。在扩大化（2 kg废旧高温合金）实验中,该方法对DD5、GH3128及退役航空发动机涡轮叶片等多种牌号高温合金均表现出优异的适应性,Ni提取率稳定在40-70%之间。此外,Mg熔体还可有效破坏高温合金废料的含Cr氧化层,为后续湿法处理创造有利条件。（3）多孔、低强度特点助力残留合金的高效浸出及酸浸液中Al³⁺、Cr³⁺脱除:残留合金多孔结构和低力学强度特性,显著提升了浸出反应的比表面积,从而有效提高浸出速率。针对残留合金中Ni、Al、Mg等元素易于浸出,Re、W、Mo、Ta、Hf元素难以浸出的特点,系统优化盐酸选择性浸出的技术参数。在最佳浸出条件下,Ni、Mg、Al的浸出率分别达到89.2%、96.4%和98.0%,而Re、W、Mo、Ta、Hf则高效富集于酸浸渣中。动力分析结果表明,Ni、Al元素的浸出过程符合Avrami模型,其表观活化能分别为70.62 k J/mol和90.72 k J/mol。分别采用化学沉淀法与P204萃取法对酸浸液中Al³⁺、Cr³⁺的高效脱除开展研究,结果表明化学沉淀法结合沉淀渣二次酸浸的策略,可在保证Al³⁺、Cr³⁺高效脱除的同时,最大限度降低Ni、Co损失。（4）基于氧化焙烧和碱熔法的酸浸渣优先提Re的研究:针对酸浸渣中富集的Re、Mo、W、Ta等元素,结合热力学计算与实验验证,开展氧化焙烧-碱浸和碱熔-萃取两种优先提Re方法的研究。结果表明,在900℃下,Re以Re₂O₇挥发物形式被有效分离,挥发率为97.4%,Mo则在900℃以上开始显著挥发。固态氧化产物经碱浸后,Mo、W的浸出率均高于82%,并在碱浸渣中实现了Ni、Co、Cr、Ta的富集。通过将碱浸渣返回酸浸液中二次浸出可进一步提高Ni、Co、Cr的浸出率。在优化的碱熔条件下Re、W、Mo、Cr等元素高效转化为水溶性钠盐,并在随后的水浸过程中具有约98%的浸出率。随后,采用丙酮作为萃取剂从水浸液中分离Re,最佳条件下Re萃取率达到98.3%,并通过KCl沉淀法制备KRe O₄晶体,实现Re的有效富集和提纯。此外,水浸渣返回盐酸体系进行二次浸出后,Ni、Co元素的浸出率分别达到98.1%和95.6%,并获得Ta含量45.9wt%的富Ta渣,为后续Ta资源的分离回收提供了原料。本论文共有图111幅,表18个,参考文献186篇更多还原

【Abstract】 Nickel-based superalloys have excellent high-temperature strength and corrosion resistance,and are widely used in aerospace and other fields.The waste nickel-based superalloys are rich in a variety of high-value metal elements such as Re,Mo,W,Ni,Co,etc.,making their recycling economically beneficial and strategically important for securing critical metal resources.However,due to the superalloy has a dense microstructure,high strength,corrosion resistance and other characteristics,the comprehensive recycling process is faced with crushing difficulties,acid consumption,low recovery rate and other challenges.Consequently,the recycling rate of nickel-based single crystal superalloys remains low in China,resulting in substantial losses of valuable metallic resources.To address the challenges of difficult recycling of waste superalloy,this study innovatively proposes a new technology route of‘metal melt extraction（MME）-acid leaching-leach solution decontamination-oxidation roasting-alkali leaching/alkali fusion-extraction’,which builds a theoretical system of superalloy recycling based on MME,and forms a highly efficient and adaptable treatment method for raw materials.It has formed a highly efficient and adaptable processing method.This method can achieve efficient separation and recovery of Ni,Co,Ta,Mo,W,Re and other metals,and provides a solid theoretical foundation and technical support for the recycling of waste nickel-based superalloy.The main innovations and contents are as follows:（1）This study proposes and implements a novel recycling strategy termed"waste-treatment-with-waste,synergistic regeneration,"by employing waste magnesium alloys as the MME medium for spent nickel-based superalloys.At 750°C and a mass ratio of magnesium alloy to superalloy of 5:1,the molten magnesium alloy exhibited significant selective dissolution of Ni,reaching extraction efficiencies up to approximately 73%,whereas Co extraction was limited to about 10%.Meanwhile,Re,W,and Mo were efficiently enriched in the porous residual alloy obtained after MME and vacuum treatment.The study elucidated the mechanism whereby the MME medium initially diffuses into theγphase of the superalloy,subsequently driven by concentration gradients towards theγ/γ′interface,selectively dissolving Ni from theγ′phase.High melting-point refractory elements,such as Ta,W,Co,and Cr,aggregated as discrete solid particles and formed a three-dimensional porous skeleton during subsequent vacuum treatment.During MME,Al from the magnesium alloy reacted with dissolved Ni to form Ni Al and Ni₂Al₃ intermetallic compounds,which served as precursors for catalytic Raney nickel synthesis.The composition and catalytic performance of the Raney nickel were significantly influenced by the amount of magnesium alloy added,with insufficient amounts leading to dominant Ni Al phases that adversely affected catalyst preparation.Using Ni-Al intermetallic compounds as precursors,mesoporous Raney nickel catalysts with a specific surface area of 40.52 m²/g and pore sizes of 1-10 nm were successfully synthesized.These catalysts exhibited 100%conversion and a target product yield of77%in the catalytic hydrogenation of 1,4-butynediol.（2）Pure magnesium（>99.9 wt%）was employed as the MME medium for recycling spent superalloys,validated at scale.The results showed that molten Mg effectively reduced the Ni content in the superalloy from approximately 60 wt%to below 20 wt%,significantly lowering mechanical strength.The process yielded a Ni-rich alloy（approximately88 wt%Ni）and a porous residual alloy enriched with high-value elements such as Re,W,and Mo,which can be effectively recovered in subsequent processes.Scale-up experiments（2 kg of spent superalloys）demonstrated excellent adaptability of this approach to various superalloy grades,including DD5,GH3128,and retired turbine blades,consistently achieving Ni extraction efficiencies of 40-70%.Furthermore,the molten Mg effectively disrupted the Cr oxide layers on superalloy surfaces,facilitating subsequent hydrometallurgical processing.（3）The porous,mechanically weak of the leach residue greatly increased its leaching effectiveness,and the removal of Al³⁺and Cr³⁺from the acid leachate.Based on differential leachability of the residual alloy elements,the optimum leaching conditions were found to be 70°C,2 mol/L HCl,and a solid-liquid ratio of 60 g/L.At these conditions,the leaching efficiencies of Ni,Al,and Mg were 89.2%,96.4%,and 98.0%,respectively,whereas Re,W,Mo,Ta,and Hf were concentrated in the leaching residue.Kinetics of leaching indicated that leaching of Ni and Al followed the Avrami model,with the activation energies of 70.62 and 90.72 k J/mol,respectively.Comparative studies of solvent extraction and chemical precipitation for the removal of Al³⁺and Cr³⁺from the leach demonstrated that chemical precipitation,followed by acid leach recycle,successfully removed Al³⁺and Cr³⁺,while minimizing the loss of Ni and Co.（4）An oxidative roasting and alkaline fusion strategy was developed to prioritize Re recovery from acid-leach residues rich in Re,Mo,W,and Ta.Thermodynamic calculations and experiments indicated that Re could be effectively volatilized as Re₂O₇（>97.4%volatilization）at 900°C,while Mo volatilization was significant only above 900°C.Subsequent alkaline leaching of solid oxidation products resulted in Mo and W leaching efficiencies above 82%,concentrating Ni,Co,Cr,and Ta in the residue.Re,W,Mo,and Cr were efficiently transformed into soluble sodium salts under optimized alkaline fusion conditions（700°C,60 wt%Na OH,alkaline agent-to-residue ratio 2:1,reaction time 60 min）,achieving approximately98%extraction efficiency.Acetone extraction was utilized to separate Re from the alkaline leachate,achieving 98.3%extraction efficiency under optimal conditions,followed by precipitation of KRe O₄ crystals with KCl.Recycling of alkaline leach residue to hydrochloric acid leaching further enhanced Ni and Co extraction efficiencies（98.1%and 95.6%,respectively）and yielded a Ta-rich residue（45.9 wt%Ta）,facilitating further recovery of Ta.更多还原