激光制备原位生长WB-CrB颗粒增强镍基复合涂层

In Situ Growth of WB-CrB Particles Reinforced Ni Matrix Composite Coatings by Laser Cladding

作者: 专业:光学 导师:晁明举 年度:2010 学位:硕士  院校: 郑州大学

Keywords

laser cladding, in situ synthesis, boride, microstructure, wear resistance

        激光熔覆原位生长陶瓷增强金属涂层是在激光照射下,通过元素与化合物之间或元素之间的原位反应,在涂层中原位生成一种或几种高弹性模量、高强度的陶瓷增强相,将金属的高韧性和陶瓷的耐蚀、耐磨、高硬等特性有机结合,从而达到强化基体的效果,大大提高材料的表面性能。激光熔覆原位自生陶瓷增强金属涂层原位形核、增强相颗粒细小且弥散分布、组织细化,与基体相容性好,界面结合力强,表面无污染,其硬度、耐磨性等均显著提高。硼化物具有极高的熔点和硬度,且硼化物具有硼原子间相互间牢固结合的特性,从而使其在高温及各种腐蚀性的环境中有较高的化学稳定性和独特的耐磨性,作为切削工具、耐磨耐腐蚀热机部件,在工程机械工业、医药、化工、轻工、纺织、消防、建材、农业、军工国防等部门得到广泛应用。本文采用激光熔覆原位生长技术制备了硼化物颗粒增强镍基涂层,对其制备工艺、组织、硬度和耐磨性等进行了系统研究,结果和主要结论如下:(1)在45#钢表面激光熔覆Ni60+(WO3+B2O3+C)混合粉末,首次成功制备出形貌良好、性能改善、原位生长WB-CrB颗粒增强的镍基复合涂层;最佳制备工艺为:(WO3+B2O3+C)含量16 wt.%,激光功率1.8 kW,离焦量50 mm,扫描速度2 mm/s;(2) Ni60+16 wt.%(WO3+B2O3+C)熔覆层组织为:原位生成的WB-CrB颗粒和Cr3C2条状相均匀分布于γ(NiFe)树枝晶基体中;(3)原位生长WB-CrB颗粒增强镍基复合涂层平均硬度HV0.31350,与纯Ni60熔覆层(平均硬度HV0.3800)相比,提高68.7%。摩擦试验表明,其耐磨性比纯Ni60涂层提高7倍。原位生长WB-CrB陶瓷颗粒增强相及其均匀分布是熔覆层硬度和耐磨性得以大大提高的关键因素。
    In situ synthesised ceramic coating by laser irradiation through in situ reaction among the elements and compounds has one or several high elastic modulus, high strength ceramic reinforcement, thus to strengthen the matrix and greatly improve the surface properties of materials by combining the high toughness of metal with the ceramics properties such as high corrosion resistance, high wear resistance, high hardness.In situ laser cladding ceramic coating is characterized by in situ nucleation, small and dispersed enhancing particulates and structure refinement, which has a good compatibility with matrix, strong bonding, surface pollution, and whose hardness, wear resistance and so on are significantly increased.Boride ceramics has high melting point and hardness, whose boron atoms combine with each other firm characteristics, making it at a high temperature and corrosive environment has high chemical stability and unique wear resistance. Due to its excellent performance, boride ceramics has already applied to most of the surface engineering of metallic materials, such as cutting tools, wear resistant heat engine components, widely used in construction machinery, and has also been widely used in the pharmaceutical, chemical, light industry, textile, fire, building materials, agricultural, military and national defense sector.In this paper, laser cladding boride was prepared in situ ceramic particle reinforced nickel based coatings, and its preparation, structure, hardness and wear resistance were systematically studied. Results and main conclusions are as follows:(1) In situ WB-CrB particle reinforced nickel matrix composite coatings with good morphology and improving performance were firstly successfully prepared on 45 steel by employing a proper amount of Ni60+(WO3+B2O3+C) doping using laser cladding. The optimum preparation techniques are 16wt.% content of (WO3+ B2O3+C)-doping,50mm defocusing length,1.8 kW laser power and 2 mm/s scanning velocity.(2) The microstructure of the Ni60+16wt.%(WO3+B2O3+C) coating is mainly composed of in-situ synthesized WB-CrB particulate phases and the Cr3C2 stripe phase uniformly dispersed in the y(NiFe) dendrite matrix.(3) The average hardness of the WB-CrB particulate reinforced composite coating was enhanced to HV0.31350, which is 68.7 percent higher than that of pure Ni60 coatings (HV0.3800). Friction tests showed that its excellent wear resistance is 7 times as high as that of pure Ni60 coatings. The improvement in hardness and wear resistance is due to the presence of a great deal of in-situ synthesized WB-CrB particles and their well distribution in the composite coatings.
        

激光制备原位生长WB-CrB颗粒增强镍基复合涂层

摘要4-5
Abstract5-6
目录7-10
第一章 绪论10-20
    1.1 引言10-11
    1.2 激光表面改性技术研究现状11-18
        1.2.1 激光表面熔凝12-13
        1.2.2 激光表面淬火13-14
        1.2.3 激光熔覆14-15
        1.2.4 激光表面合金化15-16
        1.2.5 激光冲击强化16-18
    1.3 本文研究的目的、内容和意义18-20
第二章 激光熔覆技术20-35
    2.1 激光熔覆技术概述20-21
    2.2 激光熔覆的理论基础21-23
        2.2.1 金属对激光的吸收21-23
        2.2.2 激光熔覆过程中的物理化学现象23
    2.3 激光熔覆的工艺方法23-26
        2.3.1 基材表面的预处理23
        2.3.2 对基体材料进行预热和后热处理23-24
        2.3.3 熔覆材料供给方式24-25
        2.3.4 激光熔覆工艺参数25-26
    2.4 激光熔覆的开裂问题26-30
        2.4.1 裂纹产生的原因26-28
        2.4.2 防止裂纹生成的方法28-30
    2.5 激光熔覆的应用30-32
    2.6 激光熔覆的前景32
    2.7 激光熔覆原位生长颗粒增强金属基复合涂层32-34
        2.7.1 原位生长技术32-33
        2.7.2 原位生长特点33
        2.7.3 激光熔覆原位生长陶瓷涂层33-34
    2.8 小结34-35
第三章 实验方法和材料35-42
    3.1 实验方法35-38
        3.1.1 制备熔覆层的方法和设备35
        3.1.2 组织与性能测试方法35-38
    3.2 实验材料选择38-41
        3.2.1 基体金属材料38
        3.2.2 合金粉末38-39
        3.2.3 熔覆材料39-41
    3.3 小结41-42
第四章 原位生成WB-CrB增强镍基激光熔覆层研究42-56
    4.1 实验材料及方法42-44
        4.1.1 实验材料42-43
        4.1.2 工艺参数43-44
    4.2 实验结果与分析44-55
        4.2.1 熔覆层形貌44-45
        4.2.2 显微组织45-52
        4.2.3 显微硬度52-53
        4.2.4 摩擦实验53-55
    4.3 小结55-56
第五章 全文总结56-57
参考文献57-67
致谢67-68
攻读硕士学位期间发表的论文68
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