氮对Incone1690合金组织及性能的影响

IMR OpenIR

	氮对Incone1690合金组织及性能的影响
	李硕
学位类型	博士
导师	刘奎
	2012
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	材料加工工程
关键词	690合金氮晶粒尺寸贫铬区碳化物 Alloy 690 Nitrogen Grain Size Cr Depletion Zone Carbide Precipitaion
摘要	"Inconel690合金（以下简称690合金）以其优异的抗应力腐蚀性能，取代600合金成为理想的核电蒸汽发生器传热管材料。本文采用光学显微镜、X射线衍射仪、扫描电镜、透射电镜等手段系统研究了具有不同N含量的690合金的晶粒长大以及尺寸分布，室温和高温力学性能，晶界的碳化物形貌以及晶界贫铬区的影响。研究发现N的添加对固溶处理后合金的晶粒长大倾向性及晶粒尺寸分布有很大的影响。合金经热轧后固溶处理，随着N含量的增加，合金的晶粒长大倾向性明显降低。在1050℃和1080℃固溶处理时，合金的平均晶粒尺寸分别由10ppm合金的32.3µm和51.3µm减小到300ppm的17.8µm和24.2µm，但是N含量高于300ppm后合金中出现异常长大的粗大晶粒，晶粒尺寸分布不均匀。当固溶温度升高到1100℃时，合金的晶粒分布重新变得均匀，晶粒异常长大的情况得到缓解。但是，N含量的增加，提高了合金中的TiN数量以及小尺寸（0-1µm）TiN所占的比例。当N含量从110ppm增加到1100ppm时，合金中的TiN的体积分数以及小尺寸（0-1µm）TiN所占的比例分别由0.026%和10%增加到0.06%和30.95%。 690合金冷轧后固溶处理，N影响合金晶粒长大倾向与热轧态的情况稍有不同。冷轧后，随着N含量的增加，冷轧态合金固溶处理后的晶粒尺寸先降低后增加。如1080℃固溶处理8min，含N为37ppm的合金的晶粒尺寸为54.6µm，300ppm的合金为14.63µm，110ppm的合金为21.24µm，而480ppm的合金为24.39µm。随着固溶时间的延长及固溶温度的升高，合金的晶粒尺寸均增加。但N含量的增加改变了固溶时间及温度对合金平均晶粒尺寸的影响，结果显示N含量为300ppm的合金晶粒长大倾向性最小，即固溶温度和时间对晶粒长大的影响最弱。这与合金中TiN的数量的增加提高了合金的形变储能有关。此外，N含量的变化还可显著影响固溶处理后晶粒尺寸的分布情况，随着N含量的增加，合金中小尺寸晶粒所占的比例先增加；当N含量高于300ppm时，合金中小尺寸晶粒所占的比例降低。随N含量的增加合金中小晶粒的分布比例先增加后减少。如经1080℃固溶处理8min后，含N为37ppm的合金中1.65μm-4.48μm之间的晶粒约占2.35%，110ppm和480ppm合金中1.65μm-4.48μm之间的晶粒约占4.84%，300N合金中1.65μm-4.48μm之间的晶粒约占9.9%。 690合金固溶处理后碳化物完全溶解，在随后的时效处理过程中，碳化物在晶界析出并长大。随时效处理时间的延长，晶界碳化物尺寸变大，形貌从细小半连续演变成粗大半连续分布。同时，单位长度晶界上的碳化物颗粒密度降低，颗粒的间距先减小后增加。合金中添加N后，碳化物尺寸减小，单位晶界上析出碳化物的密度变小，间距变大，N的添加抑制了碳化物的长大。由于晶界碳化物数量和形貌的变化，N的添加对晶界的贫铬区有很大的影响，随N含量的增加，晶界的最低Cr浓度明显增加，晶界Cr贫化得到缓解。随时效时间的延长，N含量为10ppm的合金的贫铬区的最低晶界Cr浓度始终增加，而N含量为300ppm的合金的贫铬区的晶界最低Cr浓度是先降低后增加，最低Cr含量出现在时效5小时后。表明N的添加延缓了晶界Cr浓度达到最低点的时间。晶界贫铬区的宽度随时效时间的增加而变宽，但N含量较高的690合金的晶界贫铬区的宽度窄于N含量较低的合金，这与N的添加降低了Cr在合金中的扩散系数有关。 N还可起到固溶强化的作用，N的添加可以显著的提高合金的强度，同时合金的塑性没有明显损害。除了N的固溶强化的原因外，研究发现N的添加还可以影响合金的错层能，进而影响合金中的孪晶数量。随N含量的增加，合金层错能先降低，当N含量高于110ppm时合金的层错能又开始增加。当合金的N含量从10ppm增加到300ppm，合金中退火孪晶的密度也由0.03个/µm，增加到0.06个/µm，这也是合金塑性随N含量的添加仅稍有降低的重要原因之一。N的添加降低了固溶处理时间对合金强度的影响。N的添加对合金高温抗拉强度影响不大，N的添加降低了合金的断面收缩率。N含量为10ppm的合金断面收缩率最大，合金的塑性最好，这与合金中TiN夹杂物数量少有关。随着温度的升高，不同N含量的合金的断面收缩率均增加，合金的塑性变好。"
其他摘要	"Nickel-based Inconel Alloy 690 (hereinafter called Alloy 690) is considered as the most ideal steam generator tubing materials in nuclear power plants，owing to its excellent resistance to intergranular stress corrosion cracking (IGSCC). The effects of nitrogen content on grain growth, grain size distribution, mechanical property, the carbide morphology and chromium depletion evolution of Alloy 690 were investigated by means of the optical microscopy (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), x-ray diffraction (XRD) and tensile testing at room and high temperatures. The microstructure of the 690 alloy containing nitrogen (hot-rolled condition) after solution treatment has been investigated. The results shows that nitrogen content have a great effect on the grain growth and grain size distribution of Alloy 690. With the increasing of the N content, the grain growth of alloy is limited after sloution annealing at 1050℃ and 1080℃ for 10min, but when nitrogen concentrations greater than 300ppm, the grain size of alloy is a mixture of relatively uniform fine and a few large, where temperature increasing to 1100℃, the grain size of 430ppm nitrogen alloy is uniform and abnormal growth of grain is restrained. The volume fraction of TiN increases and the size distribution shifts in the direction of smaller size as nitrogen content is higher. For example, when the N content increases from 110ppm to 1100ppm, the volume fraction of TiN and distribution ratio of fine scale(0-1µm) increase from 0.026% and 10% to 0.06% and 30.95%, respectively. With increasing of the N content, the grain size of cold-rolled alloys decreases first and then increases. When the N content increases from 37ppm to 300ppm, grain growth is limited, While the N content increases from 300ppm to 480ppm, grain size become large. The average grain size of alloy increases with the increase of solution treatment temperature and time. However, this effect weakens with nitrogen content up to 300ppm N and then increases. After solution treatment at 1080℃ for 8min, the fine scale of grain (1.65μm- 4.48μm ) ratio of 37ppm nitrogen alloy is 2.35%, 110ppm alloy and 430ppm alloy is 4.84%, 300ppm alloy is 9.9%. So, when the nitrogen content increases from 37ppm to 300ppm, the grain size distribution first shifts in the direction of finer grain size, after above 300ppm, it then shifts in the direction of larger grain size. The increasing temperature and holding time of solution treatment causes proportional changes in the fine grain size scale to decrease. With the increasing thermal treating time, the morphology of intergranular carbides changes from small and semi-continuous to very large and semi-continuous, the size of the carbides increases and the distance between carbides is reduced. N addition slows down the growth of carbides. With the increasing nitrogen addition, the size of the intergranular carbides is reduced and the distance between carbides becomes further. With the aging time increasing, the minimum chromium concentration at the grain boundaries containing nitrogen 10ppm decreases first and then increases. In the alloy containing nitrogen 300ppm, it increases with the increasing time. N addition causes the lowest value of the chromium concentration at the grain boundary to improve. This can be attributed to N addition due to reduction in grain size and N segregation. The alloy containing nitrogen 300ppm shows much wider chromium depleted-zones. This indicates that N addition decreases the diffusivity of Cr atoms during thermal treatments. Alloy 690 containing nitrogen exhibited appreciably high strength, while the ductility lowers a little. N addition causes the stacking fault energy decreased first and then increased. The alloy containing 110ppm of nitrogen expresses the lowest the stacking fault energy. N addition has little influence on the high temperature tensile strengths of alloy. With the test temperature increased from 950℃ to 1200℃, Alloy 690 with 10ppm N shows excellent high temperature ductility. The N addition to Alloy 690 leads to a decrease of high temperature ductility. "
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64503
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	李硕. 氮对Incone1690合金组织及性能的影响[D]. 北京. 中国科学院金属研究所,2012.