DD6合金高温持久强度与壁厚效应关系分析
发布时间：2018-09-15 19:29
【摘要】：单晶高温合金材料因其优异的高温性能,良好的抗氧化及抗腐蚀性能而成为制造先进航空发动机、燃气涡轮叶片的主要材料。随着国内外航空航天工业的发展,致使发动机的推重比不断增大、涡轮入口温度不断提高、气冷叶片结构越来越复杂、壁厚越来越薄,产生所谓的薄壁效应。因此,探究合金高温持久寿命与壁厚效应的的关系具有重要的意义,可以为预测发动机叶片的使用状态与寿命提供强有力的依据。本文所选用的材料是由北京航材院提供的DD6镍基单晶高温合金,该合金为我国自主研发的一类新型第二代高温合金。相比于国外使用的第二代单晶合金,DD6合金在高温状态下具有更加优异的高温持久性能。在980℃/250MPa的条件下,厚度为0.67mm、0.81mm和1.12mm的薄片状试样的持久寿命分别为185h、217.5h和229h。对叶片、铸块进行显微观察,比较其枝晶间距、强化相形状及尺寸等的差异,并通过测量其显微硬度,确定能否用易获得的试样形式的持久性能数据表征叶片的持久性能。结果表明：叶片、铸块的宏观形貌为枝晶组织,微观形貌为立方状的γ'强化相均匀的分布于γ基体上,两种试样的组织、硬度之间没有显著的差异。通过对比不同壁厚DD6试样在980℃/250MPa高温条件下的持久寿命,结合扫描电镜、XRD、能谱、电子探针等试验方法对持久试样断口、近断口横截面和纵截面进行形貌观察和成分分析,探究DD6合金是否具有壁厚效应并对其断裂机理进行分析。结果表明,DD6镍基单晶高温合金壁厚效应并不明显,随着壁厚的减少,试样高温持久寿命略有降低,断裂机理则是由韧性断裂与脆性断裂组合而成的混合型断裂。试样表面氧化膜的存在使试样的有效横截面积降低,进而增加试样的有效应力,加上试样纵截面微裂纹的存在及萌生于试样亚表面及内部的铸造微孔,构成试样断裂的基本原因。合金薄壁试样的持久断裂模式为“表面氧化-裂纹萌生-扩展”和“内部蠕变损伤”两者综合作用的结果。在“表面氧化-裂纹萌生-扩展”和“整体蠕变损伤”两者关系中,试样蠕变程度越大,则壁厚效应相对较小；相应的,如果“表面氧化-裂纹萌生-扩展”的作用大,蠕变的比重小,则壁厚效应相对明显。
[Abstract]:Single crystal superalloy has become the main material for the manufacture of advanced aero-engine and gas turbine blade because of its excellent high temperature performance, good oxidation resistance and corrosion resistance. With the development of aerospace industry at home and abroad, the propeller weight ratio of the engine is increasing, the inlet temperature of the turbine is increasing, the structure of the air-cooled blade is becoming more and more complex, the wall thickness is becoming thinner and thinner, resulting in the so-called thin-wall effect. Therefore, it is of great significance to explore the relationship between the high temperature rupture life and the wall thickness effect of the alloy, which can provide a powerful basis for predicting the service state and life of the engine blade. The material selected in this paper is the DD6 nickel base single crystal superalloy supplied by Beijing Aeronautical Materials Institute, which is a new type of second generation superalloy developed independently in China. Compared with the second generation single crystal alloy in foreign countries, the second generation single crystal alloy Candd6 has better high temperature rupture property at high temperature. At 980 鈩，
本文编号：2244285
[Abstract]:Single crystal superalloy has become the main material for the manufacture of advanced aero-engine and gas turbine blade because of its excellent high temperature performance, good oxidation resistance and corrosion resistance. With the development of aerospace industry at home and abroad, the propeller weight ratio of the engine is increasing, the inlet temperature of the turbine is increasing, the structure of the air-cooled blade is becoming more and more complex, the wall thickness is becoming thinner and thinner, resulting in the so-called thin-wall effect. Therefore, it is of great significance to explore the relationship between the high temperature rupture life and the wall thickness effect of the alloy, which can provide a powerful basis for predicting the service state and life of the engine blade. The material selected in this paper is the DD6 nickel base single crystal superalloy supplied by Beijing Aeronautical Materials Institute, which is a new type of second generation superalloy developed independently in China. Compared with the second generation single crystal alloy in foreign countries, the second generation single crystal alloy Candd6 has better high temperature rupture property at high temperature. At 980 鈩，
本文编号：2244285
本文链接：https://www.wllwen.com/kejilunwen/dongligc/2244285.html
