【作者】 辛保亮；

【导师】 李元元；

【作者基本信息】 华南理工大学 ， 材料加工工程， 2011， 硕士

【摘要】 Cu-17Ni-3Al-X合金是一种新型高强耐磨铜合金,其突出的特点是在高温下具有优异的耐磨性能,目前该合金现已成功应用于一些需要高温耐磨的场合。为了进一步拓展Cu-17Ni-3Al-X合金的应用范围,比如将其应用于海洋等腐蚀性环境中,需要深入研究这种合金的腐蚀行为。本文以离心铸造的Cu-17Ni-3Al-X合金为对象,对比了该合金在不同组织状态下的耐腐蚀性能差异,重点研究了具有细等轴晶组织特征的合金在不同腐蚀环境下的腐蚀行为,并将其与三种铝青铜合金（KK1、QAl10-4-4和KK3）的腐蚀行为进行对比,主要结论如下:（1）离心铸造Cu-17Ni-3Al-X合金铸锭的宏观组织由细等轴晶区、粗等轴晶区和柱状晶区组成。电子探针分析表明,铸锭中不存在宏观偏析,但是存在晶内偏析。（2）通过电化学试验和实验室浸渍试验,对比研究了Cu-17Ni-3Al-X合金铸锭中三种不同组织的耐腐蚀性能。总体来说,合金的细等轴晶区、粗等轴晶区和柱状晶区在腐蚀形态上都主要表现为均匀的全面腐蚀;在中性和酸性NaCl溶液中,粗大柱状晶的耐腐蚀性能最好,粗等轴晶次之,细等轴晶相对较差。三种组织耐腐蚀性能的差异主要是由于它们的晶粒大小不同造成的,晶粒越细小,晶界数量越多,合金越容易发生电化学反应;在强碱性NaCl溶液中,三种组织耐腐蚀性能的差异减小。（3）采用实验室浸渍试验、中性盐雾试验和电化学试验,重点研究了具有细等轴晶组织特征的Cu-17Ni-3Al-X合金的腐蚀行为。结果表明,Cu-17Ni-3Al-X合金在NaCl介质中表面能生成致密的Cu₂O膜,随着腐蚀时间的延长,Cu₂O膜外层被氧化成Cu₂（OH）₃Cl。由于Cu₂O膜对腐蚀反应的阻碍作用,Cu-17Ni-3Al-X合金的平均腐蚀速率随着腐蚀时间的延长而降低。（4）通过静态浸泡腐蚀试验和电化学试验,采用扫描电镜、X射线衍射仪分别研究了pH值和Cl-浓度变化对合金耐腐蚀性能和腐蚀行为的影响。结果表明,在NaCl溶液中,随着溶液pH值的升高,合金腐蚀速率逐渐降低,在中性和碱性溶液中,合金具有优异的耐腐蚀性能。当溶液pH值为强酸性（pH=3）时,合金表面不易形成致密的保护膜。当溶液pH值为6,8,10时,合金表面产生富镍、铝的Cu₂（OH）₃Cl和Cu₂O腐蚀产物膜。在强碱性（pH=12）溶液中,合金容易形成致密的Cu₂O膜。合金在不同pH值溶液中腐蚀速率的差异主要是合金表面生成的腐蚀产物膜致密的程度不同以及合金在电化学反应过程中阴极反应的不同引起的。此外,在酸性溶液中,合金在第二相的附近出现了晶间腐蚀。随着溶液中Cl-浓度的升高,合金的腐蚀速率增大。Cl-浓度对合金耐蚀性的影响主要是由于Cl-对合金表面生成的Cu₂O膜有很大的破坏作用,导致Cu₂O膜对合金的保护作用降低。（5）对比研究了Cu-17Ni-3Al-X合金与三种铝青铜合金（KK1、QAl10-4-4和KK3）在弱碱性NaCl溶液和中性盐雾中的耐腐蚀性能,结果表明:Cu-17Ni-3Al-X合金具有最佳的耐腐蚀性能,QAl10-4-4和KK3次之,KK1合金的耐腐蚀性能最差。这是因为Cu-17Ni-3Al-X合金在腐蚀过程中生成的Cu₂O膜能保持致密完整,而三种铝青铜合金表面形成的Cu₂O膜都在腐蚀过程中发生破裂,导致合金表面发生不均匀的全面腐蚀或点蚀。四种铜合金在电化学腐蚀过程中均发生相的选择性腐蚀,Cu-17Ni-3Al-X合金腐蚀后沿枝晶边界分布的第二相仅是轻微的凸出试样表面,而整个晶粒表面是平整的,而其他三种铝青铜腐蚀后试样表面高低不平。更多还原

【Abstract】 Cu-17Ni-3Al-X is a novel high-strength and wear-resisting copper alloy, the outstanding characteristic of which is the excellent wear resistance at elevated temperature. In order to expand the application of the alloy, for example in the marine environment, the corrosion behavior of the alloy must be investigated. In this dissertation, the comparison of corrosion behavior of the Cu-17Ni-3Al-X alloy with different macro structure was done first, then more tests were performed to study the corrosion behavior of alloy with complete fine equiaxed grains in different corrosion environments, at last the corrosion behavior of the alloy was compared with three kinds of aluminum bronzes （KK1, QAl10-4-4 and KK3）. The main conclusions are summarized as follows.（1） The transverse section of the centrifugal casting Cu-17Ni-3Al-X ingot is composed of fine equiaxed grain, coarse equiaxed grain and columnar grain. The EPMA analysis indicates that there is no macro segregation among the ingot, however, micro segregation was found within the grains.（2） The corrosion behavior of the Cu-17Ni-3Al-X alloy with different macro structure was compared by electrochemical measurements and immersion tests. Generally, the specimens composed of fine equiaxed grain, coarse equiaxed grain and columnar grain all reveals the morphologies of uniform corrosion. In the neutral NaCl and highly acid solution, the corrosion rates decrease in the following order: columnar grain, coarse equiaxed grain and fine equiaxed grain. However, in the highly alkaline solution, the difference of corrosion resistance of the alloy with different microstructures is neglectable.（3） The focus of this research is the corrosion behavior of Cu-17Ni-3Al-X alloy with complete fine equiaxed grain. By the immersion tests, neutral salt spray and electrochemical measurements, the corrosion behavior of the alloy with complete fine equiaxed grain was investigated in different corrosion environments. The results show that with the increasing of immersion time, the compact and uniform Cu₂O film is generated on the surface of the specimen. Moreover, the Cu₂O film is further oxidized to from porous and loose Cu₂（OH）₃Cl film. Thanks to the protection of the compact Cu₂O film, the average corrosion rate of the specimen in the NaCl solution decreases with the increasing of immersion time.（4） The influence of pH values and Cl- concentration on the corrosion behavior of Cu-17Ni-3Al-X alloy were also investigated respectively. The results manifest that the corrosion rates of the specimen decrease with the increasing of the pH values, and the specimens exhibit excellent corrosion resistance in neutral and alkaline NaCl solution. It was found that the product film formed on the surface of the specimens differs as the increasing of the pH values of the immersion solution. There is no compact product film on the surface of the alloy when the pH value is 3. However, the Ni-rich and Al-rich Cu₂（OH）₃Cl and Cu₂O films could be found on the surface of the alloy when the pH values range from 6 to 10. The compact Cu₂O film is easily formed when the pH of the NaCl solution is 12. In addition, the difference of the cathodic reaction also results in the decrease of the corrosion rates. Furthermore, in the acid solution, the alloy suffers from intergranular corrosion around the second phases. It was also found that the corrosion rates of the specimen increase with the rise of the Cl- concentration, which can be attributed to the deterioration of the Cl- to the protection of the Cu₂O film.（5） A comparative investigation of corrosion resistance of Cu-17Ni-3Al-X alloy and three kinds of aluminum bronzes （KK1、QAl10-4-4 and KK3） was carried out in slightly alkaline NaCl solution and the neutral salt spray atmosphere. The results show that the corrosion resistance of the four kinds of copper alloys decrease in the following order: Cu-17Ni-3Al-X, QAl10-4-4, KK3 and KK1. The Cu₂O film generated on the surface of Cu-17Ni-3Al-X alloy is uniform, while the purple Cu₂O film formed on the aluminum bronze ruptures as the increase of exposure time and that induces the local corrosion. The specimen surface morphologies suggest that the galvanic cells are set up between two phases and phase attact occurres during the electrochemical corrosion of the four kinds of copper alloys, which roughes the surface of the specimens.更多还原