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摘要：通过脉冲电沉积法在镍基高温合金上分别制备了Ni-Mo-Al-Gd（La，Sm）镀层。考察了电镀工艺条件（电流密度、频率、占空比、电镀时间、温度、pH值、转速）对Ni-Mo-Al-Gd（La，Sm）镀层Al含量的影响。与此同时，分别用扫描电子显微镜、电子能谱仪、X射线衍射仪、热膨胀系数仪对所得镀层的表面形貌、成分、物相结构、热膨胀系数进行表征和分析。得到以下结论：
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研究结果表明：当pH值为8.5，电流密度为18.5，温度为26℃，脉冲频率为5000HZ，占空比为0.6，电镀时间为20min，搅拌速度为350r/min，为制备Ni-Mo-Al-Gd镀层的较佳工艺条件；当pH值为8.2，电流密度为18.5，温度为26℃，脉冲频率为5000HZ，占空比为0.5，电镀时间为20min，搅拌速度为300r/min，为制备Ni-Mo-Al-La镀层的较佳工艺条件；当pH值为8.5，电流密度为18.5，温度为26℃，脉冲频率为5000HZ，占空比为0.6，电镀时间为20min，搅拌速度为350r/min时，为制备Ni-Mo-Al-Sm镀层的较佳工艺条件。30596
SEM结果表明：与Ni-Mo-Al合金镀层相比，Ni-Mo-Al-Gd（La，Sm）合金镀层的表面结瘤变小，表面平整。不同镀层，表面结瘤不同。EDX结果表明：Ni-Mo-Al-Gd（La、Sm）比Ni-Mo-Al镀层Ni含量少。同时，Ni-Mo-Al-Gd（La、Sm）比Ni-Mo-Al镀层Mo含量高。Ni-Mo-Al-Gd（La、Sm）比Ni-Mo-Al镀层中Al含量高。XRD结果表明：Ni-Mo-Al、Ni-Mo-Al-Sm、Ni-Mo-Al-La、Ni-Mo-Al-Gd镀层均为晶态结构。热膨胀曲线结果表明：Ni-Mo-Al-Gd（La、Sm）镀层比Ni-Mo-Al镀层具有更好的耐高温性能。不同镀层在20-1300℃范围内的工程热膨胀系数大小排序为：Tα(Ni-Mo-Al-Gd)＜Tα(Ni-Mo-Al)＜Tα(Ni-Mo-Al-Sm)＜Tα(Ni-Mo-Al-La)。
毕业论文关键词：脉冲电沉积；稀土；Al；热膨胀系数
Study on Preparation of Ni-Mo-Al-Gd Alloy Coating
Abstract：In this paper , Ni-Mo-Al-Gd（La，Sm） composite coatings were prepared as the bond coating by pulse plating method. The effect of the electroplating process conditions (current density, frequency, duty cycle, plating time, temperature, pH, speed) on the Al content of Ni-Mo-Al-Gd（La，Sm）coating were studied。At the same time, the surface morphology, composition, phase structure, thermal expansion coefficient were characterized and analyzed by the SEM, EXD, XRD, thermal expansion coefficient.From the research,the conclusions are as follows:
The results showed that when the pH value is 8.5, the current density is 18.5, the temperature is 26 ℃, the pulse frequency is 5000HZ, the duty ratio is 0.6, the plating time is 20min, the stirring speed is 350r/min, the Al content of Ni-Mo-Al-Gd coating is the highest; when the pH value is 8.2, the current density is 18.5, the temperature is 26 ℃, the pulse frequency is 5000HZ, the duty ratio is 0.5, the plating time is 20min, the stirring speed is 300r/min, the Al content of Ni-Mo-Al-Gd coating is the highest; when the pH value is 8.5, the current density is 18.5, the temperature is 26 ℃, the pulse frequency is 5000HZ, the duty ratio is 0.6, the plating time is 20min, the stirring speed is 350r/min, the Al content of Ni-Mo-Al-Gd coating is the highest.
SEM results indicated that relative to Ni-Mo-Al coating, the cracks of the Ni-Mo-Al-Gd（La，Sm） coating surface become smaller and more smooth. Different coatings have different surface nodulation. EDX results shows that compared to the Ni-Mo-Al coating, the Ni content of Ni-Mo-Al-Gd（La，Sm） plating were reduced. At the same time, compared to the Ni-Mo-Al coating, the Mo content of Ni-Mo-Al-Gd（La，Sm） plating were increased. Compared to the Ni-Mo-Al coating, the Al content of Ni-Mo-Al-Gd（La，Sm） plating were increased. XRD indicates that Ni-Mo-Al、Ni-Mo-Al-Sm、Ni-Mo-Al-La、Ni-Mo-Al-Gd coatings are crystalline. The thermal expansion curve shows that: as compared with Ni-Mo-Al coating, Ni-Mo-Al-Gd (La, Sm) coating having good high temperature performance. The engineering thermal expansion coefficient of the different coatings in the range of 20-1300℃ was in order: Tα(Ni-Mo-Al-Gd)＜Tα(Ni-Mo-Al)＜Tα(Ni-Mo-Al-Sm)＜Tα(Ni-Mo-Al-La)