用于镍基高温合金熔炼氧化锆耐火材料的研究

发布时间：2018-03-25 14:35

本文选题：镍基高温合金熔炼　切入点：耐火材料　出处：《上海大学》2017年博士论文

【摘要】：航空发动机生产被视为国家战略性产业,而镍基高温合金是航空发动机的重要保障。为了保证航空发动机的可靠性,国内外对高温合金中气体和杂质含量都有严格的要求。但在杂质控制水平方面,我国与国际水平仍有较大差距。因此,提高镍基合金的高温冶金质量具有重要意义。真空感应熔炼是生产高温合金的基本方法。目前广泛使用的MgO和Al_2O_3坩埚耐火材料,存在高温合金熔体与坩埚耐火材料的反应,污染了合金熔体,从而影响母合金的纯净度,降低合金的使用性能。从高温合金纯净化熔炼角度考虑,本文旨在研发适用于镍基高温合金熔炼的氧化锆耐火材料,以减小耐火材料对合金质量的影响。经过文献调研,氧化镁部分稳定氧化锆(MgO-PSZ)材料具有潜在的应用前景。本研究涉及MgO-PSZ的成型与烧结工艺和掺杂不同MgO含量的MgO-PSZ的性能的评价,并从高温热模拟侵蚀实验和真空感应熔炼实验两个角度研究了MgO-PSZ作为高温合金熔炼用耐火材料的可行性。实验过程中提出MgO-PSZ的侵蚀机理。同时针对侵蚀机理提出Al_2O_3掺杂改进MgO-PSZ耐侵蚀性的解决措施,并探讨了Al_2O_3掺杂改进MgO-PSZ耐侵蚀性的机制。论文通过分析MgO-PSZ素坯热收缩和TG-DSC曲线,优化了MgO-PSZ烧结工艺。对不同MgO(2.3 wt%、2.7 wt%、3.5 wt%和4.0 wt%)掺杂量的MgOPSZ性能进行了评价,得出当MgO掺杂含量为3.5 wt%时,MgO-PSZ强度与杨氏模量的比值最大,热膨胀曲线呈线性变化,具有较好的抗热震性。通过高温热模拟侵蚀实验研究了3.5 wt%MgO-PSZ与K403镍基高温合金的界面行为。研究表明:3.5 wt%MgO-PSZ基片与K403镍基高温合金发生反应,生成Al_2O_3,而部分Al_2O_3又与基片中的MgO反应生成Mg Al2O4。3.5 wt%MgOPSZ经镍基高温合金循环侵蚀后,表面发生破损剥落。针对该问题,提出了3.5wt%MgO-PSZ的侵蚀破损机制。3.5 wt%MgO-PSZ基片侵蚀破损是由镍基高温合金熔体对3.5 wt%MgO-PSZ的化学侵蚀和热循环对3.5 wt%MgO-PSZ的热侵蚀共同导致。其中,镍基高温合金熔体对3.5 wt%MgO-PSZ的化学侵蚀是导致3.5 wt%MgO-PSZ基片侵蚀破损的主要因素,而热循环则加速基片的侵蚀破损。针对侵蚀破损机制,提出Al_2O_3掺杂改善3.5 wt%MgO-PSZ耐侵蚀性的解决途径,并评价Al_2O_3不同掺杂含量对3.5 wt%MgO-PSZ耐侵蚀性的改善效果。当基片中Al_2O_3的掺杂量为0.8 wt%时,其循环使用次数由3次提高至8次,材料的耐侵蚀性达到最佳。同时探讨Al_2O_3掺杂改善3.5 wt%MgO-PSZ耐侵蚀性机制。从化学侵蚀角度,Al_2O_3掺杂剂与3.5 wt%MgO-PSZ中的MgO在基体中生成Mg Al2O4,提高了MgO在3.5 wt%MgO-PSZ基体中的稳定性,使得基片中MgO向界面扩散减慢,从而减缓了界面产物Al_2O_3与3.5 wt%MgO-PSZ中MgO的反应,即减小了化学反应对基片的侵蚀,改善了基片的耐侵蚀性。从热循环角度,掺杂适量Al_2O_3有助于提高MgO-PSZ的热循环稳定性。这两方面因素共同作用改善了MgO-PSZ耐镍基高温合金侵蚀性能。采用掺杂0.8 wt%Al_2O_3的3.5 wt%MgO-PSZ坩埚材料真空感应熔炼实验镍基高合金,验证实际冶炼过程中坩埚耐火材料对镍基高温合金氧含量的影响。结果表明掺杂0.8 wt%Al_2O_3的3.5 wt%MgO-PSZ展现了更好的化学稳定性,基本没有向合金液供氧。该现象与热力学分析结果相一致。综合上述分析,作为熔炼镍基高温合金的耐火材料,掺杂0.8 wt%Al_2O_3的3.5 wt%MgO-PSZ材料具有较好的耐侵蚀性和热循环稳定性,展现了潜在的应用前景。
[Abstract]:Aero engine production is regarded as a national strategic industry, and the nickel base superalloy is an important guarantee for aero engine. In order to ensure the reliability of both at home and abroad on gas and impurity content in high temperature alloy has strict requirements. But in control of impurity level, our country and the international level there are still large gaps. Therefore, it is of great significance to improve the metallurgical quality of high temperature nickel base alloy. Vacuum induction melting is a basic method for production of high temperature alloy. The widely used MgO and Al_2O_3 crucible refractory material, there is high temperature alloy melt and crucible refractory reaction, pollution of the alloy melt, thus affecting the purity of the master alloy, reduce the use of properties of the alloy. From the high temperature alloy. The purity of melting point of view, this paper aims to develop zirconia refractories used for smelting nickel base superalloy, to reduce the refractory material of the alloy The quality of influence. Through literature research, Magnesium Oxide partially stabilized zirconia (MgO-PSZ) material has potential application prospect. To evaluate the performance of this study relates to MgO-PSZ molding and sintering process and doped with different content of MgO MgO-PSZ, and from the high temperature thermal simulation of MgO-PSZ as high temperature alloy smelting with feasibility of refractories. Erosion two the point of view of experiment and vacuum induction melting experiment of erosion mechanism of MgO-PSZ is proposed in the course of the experiment. At the same time according to the corrosion mechanism of Al_2O_3 doped MgO-PSZ presents improved corrosion resistance measures, and discusses the improvement of Al_2O_3 doped MgO-PSZ resistance mechanisms to corrosion. By analyzing MgO-PSZ compacts thermal shrinkage and TG-DSC curve, the optimization of MgO-PSZ sintering process. On different MgO (2.3 wt%, 2.7 wt%, 3.5 wt% and 4 wt%) properties of MgOPSZ doping amount was evaluated when the MgO content is 3.5 wt%, MgO- Young's modulus and strength of PSZ maximum ratio, thermal expansion curve changes linearly, has good thermal shock resistance. Through thermal simulation of interfacial behavior of 3.5 wt%MgO-PSZ and K403 nickel base superalloy was investigated. The results show that the erosion experiment: 3.5 wt%MgO-PSZ substrate and K403 nickel based superalloy reacts to generate Al_2O_3, and some Al_2O_3 and Mg Al2O4.3.5 and MgO reaction in the wt%MgOPSZ substrate with nickel base superalloy cyclic erosion after surface damage spalling. Aiming at this problem, put forward the 3.5wt%MgO-PSZ.3.5 wt%MgO-PSZ substrate breakage mechanism of erosion erosion damaged by nickel based high temperature alloy thermal erosion chemical corrosion and heat cycle on 3.5 wt%MgO-PSZ on the 3.5 wt%MgO-PSZ common cause. The chemical corrosion of nickel based high temperature alloy melt to 3.5 wt%MgO-PSZ are the main factors causing 3.5 wt%MgO-PSZ substrate erosion damage, and heat Cycle accelerated erosion substrate damage. For erosion damage mechanism, proposed Al_2O_3 doping improved 3.5 wt%MgO-PSZ resistant corrosive solution, and to evaluate different Al_2O_3 doping content corrosion effect on 3.5 wt%MgO-PSZ. When the doping amount of Al_2O_3 in the substrate is 0.8 wt%, the cycle number rose from 3 times to 8 times, the erosion resistance of materials to achieve the best. At the same time to explore the influence of Al_2O_3 doping wt%MgO-PSZ 3.5 corrosion mechanism. From the angle of chemical erosion, Al_2O_3 dopant and wt%MgO-PSZ in the 3.5 generation of Mg Al2O4 MgO in the matrix, improve the stability of MgO 3.5 in the wt%MgO-PSZ matrix, the substrate MgO to interface diffusion slow down, thus slowing the interface product of Al_2O_3 and 3.5 wt%MgO-PSZ MgO reaction, which reduced the erosion of chemical reaction on the substrate, the substrate to improve the corrosion resistance. From the angle of thermal cycling, doping amount of Al _2O_3 helps to improve the thermal stability of MgO-PSZ. The interaction of these two factors to improve the MgO-PSZ resistance of Ni based high temperature alloy corrosion performance. By doping 0.8 wt%Al_2O_3 3.5 wt%MgO-PSZ vacuum induction melting crucible material experiment of nickel - base alloy, validate the effect the crucible refractory material in the smelting process of the actual oxygen content of nickel based superalloy. Results show that the 0.8 wt%Al_2O_3 doped 3.5 wt%MgO-PSZ showed better chemical stability, no oxygen supply to the alloy liquid. This phenomenon and the thermodynamic analysis results are consistent. Based on the above analysis, the refractory material smelting of nickel based superalloy, 0.8 wt%Al_2O_3 doped 3.5 wt%MgO-PSZ material has good corrosion resistance and thermal stability, show the potential application prospects.

【学位授予单位】：上海大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TF815;TQ175.7

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