| Nb2O5对铁基合金激光熔覆层裂纹敏感性的影响 |
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| 引用本文： | 晁明举,余菊美,梁二军,袁斌.Nb2O5对铁基合金激光熔覆层裂纹敏感性的影响[J].激光技术,2005,29(6):568-571. |
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| 作者姓名： | 晁明举 余菊美 梁二军 袁斌 |
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| 作者单位： | 1.郑州大学, 物理工程学院, 教育部材料物理重点实验室, 郑州, 450052 |
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| 基金项目： | 河南省高校创新人才基金资助项目(1999-125)，河南省高校青年骨干教师资助计划项目基金资助(2003-218) |
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| 摘 要： | 在45#钢基底上进行了铁基合金和铁基合金加Nb2O5的激光熔覆对比实验.通过工艺参数和Nb2O5含量的优选,获得了成形良好、无裂纹、组织致密均匀的高质量铁基激光熔覆层.采用渗透法观察熔覆层表面裂纹,利用金相显微镜和扫描电镜观察熔覆层横断面的显微组织,使用X射线衍射仪对熔覆层进行物相分析,并测试了熔覆层的硬度.分析结果表明,G312+0.6%Nb2O5(质量分数)熔覆层组织为细小的先共晶析出的碳化物等强化相均匀分布在由γ(Fe,Ni)固溶体和多种金属间化合物组成的共晶体中,且生长方向不同.Nb2O5改善铁基熔覆层抗开裂能力的原因一方面是Nb占据晶界增强了晶界结合,另一方面,部分Nb2O5受C的还原作用生成NbC,先共晶析出,成为异质核,提高了凝固结晶过程中的形核率,使得熔覆层组织得以细化,且降低了熔体中的C浓度,减少了Cr(Fe)碳化物脆性相的体积分数,熔覆层韧性增强,裂纹敏感性降低.
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| 关 键 词： | 激光熔覆 裂纹 显微组织 铁基合金 Nb2O5 |
| 文章编号： | 1001-3806(2005)06-0568-04 |
| 收稿时间： | 2004-09-17 |
| 修稿时间： | 2004-10-25 |
Effect of Nb2O5 on the cracking susceptibility of laser-clad Fe-based coating |
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| CHAO Ming-ju,YU Ju-mei,LIANG Er-jun,YUAN Bin.Effect of Nb2O5 on the cracking susceptibility of laser-clad Fe-based coating[J].Laser Technology,2005,29(6):568-571. |
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| Authors: | CHAO Ming-ju YU Ju-mei LIANG Er-jun YUAN Bin |
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| Affiliation: | Key Laboratory of Material Physics of Ministry of Education, Department of Physics, Zhengzhou University, Zhengzhou 450052, China |
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| Abstract: | The experiments of laser-clad Fe-based alloy powder doped with and without Nb2O5 on medium carbon steel 45 by powder feeding are carried out.A crack-free,fine and homogeneous Fe-based coating is obtained at a proper amount of Nb2O5-doped under suitable optimizing processing parameters.The effect on microstructure of different amounts of Nb2O5 to Fe-based coating is studied with scanning electron microscopy,optical microscopy and Xray diffraction.The cracking on the surface of the coatings is observed and the hardness in the cross-section of the clad layers is measured.It is reveled that lots and lots of fine dendritic crystal grown along different directions in the cladding layers of G312+0.6% Nb2O5(mass fraction) are uniformly dispersed in the matrix,which is a mixture containing γ(Fe,Ni) solid-solution and chromium carbide or boride.It is considered that the improvement of properties of the coating is due to the following two reasons.On the one hand,Nb atoms can enhance intercrystalline cohesion when they are located in the crystal boundary.On the other hand,particles of NbC,reduced from Nb2O5 by C at high temperature and deposited primarily from the alloy solution,become new crystalline nuclei and increase the nuclear rate in solidification,which leads to the dendritic turn to fine.The cracking susceptibility of the Fe-based coating doped a proper content of Nb2O5 can be reduced because of the decrease in amount of crisp parts in the layers and increase in tenacity of the coatings. |
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| Keywords: | laser cladding crack microstructure Fe-based alloy Nb_2O_5 |
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