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摘要 自从二十世纪中期以来激光技术的快速发展，兴起了激光熔敷这一项新型的表面改进技术。激光熔敷不仅适用性广，能节约大量贵金属资源，而且易实现自动化生产。本课题在16Mn 钢表面激光熔敷一层 WC 涂层，研究不同扫描速度对熔敷层表面成型的影响。通过使用 SEM 和EDS 对熔敷区域微观组织变化进行观察，用显微硬度计测量并比较不同扫描速度下的硬度变化，分析 WC 熔敷层高温摩擦磨损性能。 通过实验发现，适当的扫描速度使熔敷层的硬度有了明显改善，能提高五倍。扫描速度在 3mm/s 时，激光照射时间长，容易引起晶粒粗化。而 5mm/s 以上的扫描速度可能造成熔敷层存在未熔化的粉末颗粒。熔敷层高温下的磨损性能也有了提高，主要是因为WC 颗粒对表面的支撑和保护作用，氧化膜的出现也对磨损性能有益。通过研究分析，发现裂纹的形成主要是因为热应力，组织应力和残余应力的综合作用，并且多道搭接比单道熔敷更容易出现裂纹。 58967
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毕业论文关键字：WC 熔敷层；裂纹；硬度；摩擦磨损；显微组织
Abstract Since the rapid development of laser technology in the middle of twentieth Century, laser cladding is a new surface modification technology. Laser cladding is not only suitable for wide application, saving a large amount of precious metal resources, but also easy to realize automatic production. In this paper, a layer of WC coating was deposited on the surface of 16Mn steel by laser cladding, and the influence of different scanning speeds on the surface forming of the cladding layer was studied. By using SEM and EDS ,we observe the microstructure changes of deposited area. The hardness variation of different scanning speed was measured and compared with the micro hardness tester. The friction and wear properties of WC melt layer at high temperature were analyzed. Through the experiment, it is found that the hardness of cladding layer can be improved obviously by the appropriate scanning speed, which can be improved by five times. When the scanning speed is 3mm/s, the laser irradiation time is long, and it is easy to cause the grain coarsening. The scanning speed of 5mm/s may result in the presence of melt powder particles in the cladding layer. The wear resistance of cladding layer has been improved, mainly because of the support and protection of WC particles on the surface. The appearance of the oxide film is also beneficial to the wear performance. Through research and analysis, it is found that the formation of cracks is mainly due to the combined effects of thermal stress, tissue stress and residual stress.
Key words: WC cladding; crack; hardness; friction and wear; microstructure
目录
第一章绪论1
1.1引言..1
1.2激光熔敷技术1
1.2.1激光熔敷的特点...2
1.2.2激光熔敷的应用...3
1.3本课题的研究现状..4
1.4本次课题的研究目的、内容与意义....5
1.4.1研究目的5
1.4.2本次课题的主要研究内容..5
1.4.3研究意义6
1.5激光熔敷研究中存在的问题与研究展望.6
1.5.1涂层剥落与烧损的问题.6
1.5.2涂层开裂的问题...7
1.5.3激光工艺参数选择的问题..7
1.5.4激光熔敷研究展望....7
第二章实验准备及实验方法9
2.1实验材料...9
2.1.1基体实验材料..9
2.1.2熔敷粉末材料..9
2.2实验设备.10
2.2.1激光器..10
2.2.2送粉器..11
2.3实验方案的设计....12
2.4试验分析方法...12
2.4.1试样的切割与镶嵌..12
2.4.2金相磨样与分析.13
2.4.3显微硬度测试14
2.4.4摩擦磨损性能测试..15