一种含C镍基单晶高温合金的热处理工艺研究
发布时间：2018-08-31 12:55
【摘要】：镍基单晶高温合金作为一种具备高温下抗蠕变、抗腐蚀、抗氧化等能力的金属材料,被广泛应用于航空发动机及地面燃气轮机的热端部件。前期研究表明,镍基单晶高温合金的微观组织对其力学性能有着重要的影响,而少量C元素的添加及热处理工艺对合金显微组织有很大影响。因此,本文以含C的第三代镍基单晶高温合金DD90为研究对象,通过调整合金中微量C元素的含量及改变热处理工艺,研究C含量对合金凝固路径、凝固特征温度、枝晶组织、共晶组织和碳化物相的影响。采用不同的热处理工艺,研究不同热处理工艺对合金显微组织、共晶组织及γ'相的影响以及分析热处理前后碳化物形态的演变。得到以下主要结论:1、合金中C元素的添加使得合金的液相线温度、固相线温度、碳化物溶解温度和γ'相溶解温度均有所降低。此外,合金的结晶温度区间对C元素的敏感程度不高,随C含量的增加,其变化幅度不大。2、C含量对合金的枝晶间距的影响不大。随着C含量的增加,合金中共晶组织体积分数呈降低趋势,碳化物相含量呈增加趋势且其尺寸变大,同时C元素的添加对合金γ'相的分布、尺寸和形貌没有明显影响。C含量低的合金其碳化物呈颗粒状或块状;当含C量较高时,碳化物呈汉字体状。3、由于C元素的添加,使得合金凝固特征温度降低。经相同热处理后的不同C含量合金,其C含量越高的合金其枝晶消失程度越高。同时,随着C含量的增加,合金枝晶溶解越完全,共晶消除程度越高。且随C含量的增加,合金热处理态γ相尺寸随之增大,γ'相数量逐渐减少。4、合金经不同制度的热处理后,均实现合金成分均匀化的目的,且偏析程度显著降低。此外,随着热处理温度的升高,合金中枝晶组织的轮廓逐渐变得模糊。当固溶温度设定在1305℃及以上时,合金的枝晶轮廓几乎完全消失。在采取最高温度为1305℃的多步热处理制度后,该合金中的共晶组织含量最低,且合金的γ'相具有好的立方度,高体积分数。5、合金经热处理后碳化物与铸态碳化物成分基本一致,表明在热处理过程中,碳化物仅发生分解,进而使得碳化物尺寸变小且趋于弥散分布。多步固溶处理的热处理为碳化物分解提供了足够的时间,与铸态碳化物相比,热处理态碳化物尺寸减小;当提高热处理温度时,碳化物分解程度提高,合金中的碳化物形貌更为简单,且尺寸明显减小,碳化物主要以细小颗粒状弥散分布。
[Abstract]:As a kind of metal material with high temperature resistance to creep, corrosion and oxidation, nickel base single crystal superalloy is widely used in the hot end parts of aero-engine and ground gas turbine. The previous studies show that the microstructure of Ni-base single crystal superalloy has an important influence on its mechanical properties, while the addition of a small amount of C element and the heat treatment process have great influence on the microstructure of the alloy. Therefore, the effect of C content on solidification path, solidification characteristic temperature and dendrite structure of the third generation nickel base single crystal superalloy (DD90) was studied by adjusting the content of trace C in the alloy and changing the heat treatment process, so as to study the effect of C content on the solidification path, solidification characteristic temperature and dendrite structure of the alloy. Effect of eutectic structure and carbide phase. The effects of different heat treatment processes on the microstructure, eutectic structure and 纬 'phase of the alloy were studied, and the evolution of carbide morphology before and after heat treatment was analyzed. The main conclusions are as follows: 1. With the addition of C element in the alloy, the liquid phase line temperature, the solid phase line temperature, the carbide dissolution temperature and the 纬 'phase dissolution temperature are all decreased. In addition, the crystallization temperature range of the alloy is not sensitive to element C, and with the increase of the content of C, the extent of the change is not significant. The effect of the content of 2C on the dendrite spacing of the alloy is not significant. With the increase of C content, the volume fraction of eutectic microstructure decreases, the content of carbide phase increases and its size increases, and the distribution of 纬 'phase of alloy is affected by the addition of C element. The carbides of the alloys with low content of .C have no obvious effect on size and morphology, and the carbides are like Chinese characters when the content of C is high, and the solidification characteristic temperature of the alloys decreases because of the addition of C elements. After the same heat treatment, the higher the C content, the higher the degree of dendrite disappearance. At the same time, with the increase of C content, the more complete the dendrite dissolution, the higher the degree of eutectic elimination. With the increase of C content, the size of 纬 phase in heat-treated alloy increases, and the number of 纬 'phase decreases by .4.After heat treatment in different systems, the composition of the alloy is homogenized and the segregation degree is reduced significantly. In addition, with the increase of heat treatment temperature, the outline of dendritic structure in the alloy becomes blurred. When the solution temperature is set at 1305 鈩，
本文编号：2215050
[Abstract]:As a kind of metal material with high temperature resistance to creep, corrosion and oxidation, nickel base single crystal superalloy is widely used in the hot end parts of aero-engine and ground gas turbine. The previous studies show that the microstructure of Ni-base single crystal superalloy has an important influence on its mechanical properties, while the addition of a small amount of C element and the heat treatment process have great influence on the microstructure of the alloy. Therefore, the effect of C content on solidification path, solidification characteristic temperature and dendrite structure of the third generation nickel base single crystal superalloy (DD90) was studied by adjusting the content of trace C in the alloy and changing the heat treatment process, so as to study the effect of C content on the solidification path, solidification characteristic temperature and dendrite structure of the alloy. Effect of eutectic structure and carbide phase. The effects of different heat treatment processes on the microstructure, eutectic structure and 纬 'phase of the alloy were studied, and the evolution of carbide morphology before and after heat treatment was analyzed. The main conclusions are as follows: 1. With the addition of C element in the alloy, the liquid phase line temperature, the solid phase line temperature, the carbide dissolution temperature and the 纬 'phase dissolution temperature are all decreased. In addition, the crystallization temperature range of the alloy is not sensitive to element C, and with the increase of the content of C, the extent of the change is not significant. The effect of the content of 2C on the dendrite spacing of the alloy is not significant. With the increase of C content, the volume fraction of eutectic microstructure decreases, the content of carbide phase increases and its size increases, and the distribution of 纬 'phase of alloy is affected by the addition of C element. The carbides of the alloys with low content of .C have no obvious effect on size and morphology, and the carbides are like Chinese characters when the content of C is high, and the solidification characteristic temperature of the alloys decreases because of the addition of C elements. After the same heat treatment, the higher the C content, the higher the degree of dendrite disappearance. At the same time, with the increase of C content, the more complete the dendrite dissolution, the higher the degree of eutectic elimination. With the increase of C content, the size of 纬 phase in heat-treated alloy increases, and the number of 纬 'phase decreases by .4.After heat treatment in different systems, the composition of the alloy is homogenized and the segregation degree is reduced significantly. In addition, with the increase of heat treatment temperature, the outline of dendritic structure in the alloy becomes blurred. When the solution temperature is set at 1305 鈩，
本文编号：2215050
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