【作者】 陈伟；

【导师】 陈光； 楼琅洪； 李辉；

【作者基本信息】 南京理工大学 ， 材料学， 2007， 博士

【摘要】 新一代高推重比航空发动机对燃烧室机匣部件性能和承温能力提出了更高的要求。机匣整体精铸工艺有望克服现行传统锻焊成形机匣刚性差、变形严重的不足,进一步降低重量、提高推重比,更易实现高推重比发动机的复杂结构;而传统机匣大量使用的Inconel 718及替代合金也不能满足新一代高推重比发动机的使用要求。因此发展能够在700℃保持组织和性能稳定、室温至700℃屈服强度均超过1000MPa,且适于整体精铸成形的高强度铸造高温合金具有重大的实际意义。本文在Inconel 718C和Rene 220合金基础上,采用理论计算与实验相结合的方法,设计了一系列改型合金成分;并系统研究了Nb、Ta、W、Mo、Al、Ti等元素含量变化对力学性能、长期时效过程中的组织稳定性和时效硬化行为的影响规律以及熔体处理工艺、热处理工艺对试验合金组织和力学性能的影响规律,得到如下主要结果:（1）保持（Nb+Ta/2）%wt不变,随Ta含量增加,室温和700℃拉伸强度、700℃持久寿命显著提高,合金中γ”相稳定性提高,δ相的析出被推迟,同时低Ta合金中的700℃时效硬化峰在高Ta合金中不再出现,这说明相同原子比的Ta置换Nb既有利于合金强化、又有利于组织稳定性的提高。但当保持Nb含量不变时增加Ta含量,虽然合金拉伸强度和持久寿命显著提高,γ”相稳定性却降低,δ相加速析出,700℃时效硬化峰提前出现,这说明Nb、Ta总原子百分比的提高降低了合金的组织稳定性。（2）保持Mo含量不变而增加W含量对室温和700℃拉伸强度、700℃持久寿命影响不大,却显著降低γ”相稳定性,强烈促进δ相提前析出,加速700℃时效硬化峰出现。但保持（Mo+W/2）%wt不变,增加W含量时,室温和700℃拉伸强度、700℃持久寿命均显著提高,晶界δ相虽提前析出,却不如单独增加W显著,并且700℃时效至1000小时仍未出现硬化峰,说明该成分合金中γ”相仍具有较好的组织稳定性。（3）增加Ti含量显著提高室温和700℃拉伸强度,但同时显著降低700℃持久寿命、明显促进δ相析出、降低γ”相稳定性、加速700℃时效硬化峰出现。而增加Al含量显著降低合金持久寿命,但对室温和700℃强度、组织稳定性以及时效硬化行为的影响却不显著。（4）设计优化的高温合金成分为Ni_56.415Cr_18.0Co_12.0Al_0.5Ti_1.0Nb_3.0Ta_5.0Mo_2.0W_2.0B_0.02-Y_0.05C_0.015,采用铸造工艺为1600℃保温熔体处理10分钟、浇注温度1400℃、模壳预热温度800℃,热处理工艺为1180℃×4小时→775℃×4小时→700℃×10小时。该合金700℃屈服强度达1075MPa,700℃/620MPa持久寿命达到250小时,明显优于Inconel 718C合金650℃水平。与Rene 220合金相比,室温屈服和断裂强度分别提高35%和29%,700℃屈服和断裂强度分别提高34%和27%,700℃/620MPa持久寿命提高355%。经700℃1000小时长期时效后,该合金强度和持久性能仍能保持与时效前水平相当,满足新一代高推重比航空发动机精铸燃烧室机匣用材要求。更多还原

【Abstract】 Latest high thrust-weight ratio aeroengine put forward higher requirements for enduring temperature of the structure material of the combustor casing.Inconel 718,among with the substituted alloys,couldn’t meet the requirements of the latest high thrust-weight ratio aeroengine. Therefore,there is an urgent demand for the research and development of a kind of high-strength nickel-based cast superalloy,which should acquire the stability of microstructure and mechanical properties up to 700℃,and the yield strengthes of more than 1000MPa up to 700℃.Based on Inconel 718C and Rene 220,series of modified chemical compositions were designed through theoretical calculation and experiments. Effects of casting procedures and heat-treatment procedures on microstructures and mechanical properties,as well as effects of elements adjustment on mechanical properties,microstructure evolution and hardening behavior during long term exposure,were systematically investigated in experimental alloys.The results are showed as below.（1）Replacing Nb with same atom percent of Ta,improved strengthening effects and microstructure stability were obtained.With the same（Nb+Ta/2） %wt,increased Ta led to remarkable improvement of the tensile properties, stress-rupture properties,stability ofγ" and retarded precipitation ofδ.Also, the hardness peak,which occurred in the alloy with lower Ta%wt, disappeared in the alloy with higher Ta%wt.On the other hand,increased （Nb+Ta/2）%wt decreased the microstructure stability of the experimental alloy.With the same Nb%wt,increased Ta%wt improved the tensile and stress-rupture properties remarkably,while it decreased the stability ofγ" and accelerate the precipitation ofδ,and advanced the occurrence of hardness peak during ageing at 700℃.（2）With the same Mo%wt,increased W%wt show no evident improvement on tensile and stress-rupture properties,while it decreased the stability ofγ" and accelerate the precipitation ofδand the occurrence of hardness peak during ageing at 700℃.On the other hand,with the same（Mo +W/2）%wt,increased W led to remarkable improvement of the tensile properties,stress-rupture properties.In some extent,the precipitation ofδwas accelerated,while it was not as remarkably as that of the alloy with increased （Mo+W/2）%wt.And the hardness peak disappeared,which showed acceptable microstructure stability.（3）The alloy with increased Ti%wt showed evidently higher tensile strength at both room temperature and 700℃,decreased stress-rupture properties at 700℃,lower stability ofγ",accelerated precipitation ofδand hardness peak.Increasing Al%wt decreased the stress-rupture properties, while it showed no evident change on tensile properties,microstructure stability and aging hardening behavior.（4）Ni_56.415Cr_18.0Co_12.0Al_0.5Ti_1.0Nb_3.0Ta_5.0Mo_2.0W_2.0B_0.02Y_0.05C_0.015was the eventually chosen chemical composition.Its yield strength at 700℃exceeded 1000MPa,which was superior to that of Inconel 718C at 650℃.Comparing to Rene 220,experimental alloy also showed obvious advantage in properties: 35%and 29%improvement of yield strength and tensile strength at 25℃, 34%and 27%improvement of yield strength and tensile strength at 700℃and 355%improvement of stress-rupture life at 700℃/620MPa.Also,the modified alloy could maintain its mechanical properties even after long-time exposure at 700℃for 1000 hours.更多还原