【作者】 付春霞；

【导师】 姜江；

【作者基本信息】 山东大学 ， 材料学， 2008， 硕士

【摘要】 激光快速成形技术是在快速原型技术和激光熔覆技术的基础上发展起来的一项高新制造技术。目前,激光熔覆及快速成形采用的材料主要沿用传统的喷涂系列合金,已不能满足生产实际的需要,因此研究和开发新型的符合资源优化配置、满足性能要求的熔覆材料将是当务之急。工艺研究是激光熔覆及快速成形的基础部分。本课题首先研究了激光功率、扫描速度、搭接率、Z轴增量、送粉率等工艺参数对成形尺寸、成形质量的影响。确定最佳的工艺参数如下:送粉速率:10g/min;激光功率:1400-1500W;扫描速度:5mm/s;光斑直径:3mm;搭接率:50%;Z轴增量:0.3mm。其次,根据成形材料设计原则并参考市场上用于熔覆的材料的构成特点,通过试验初步确定成形材料的成分组成,研究了Y₂O₃对铁基激光熔覆及快速成形件组织、物相构成、耐磨性以及外貌特征的影响。研究表明:Y₂O₃的加入可以明显细化组织,使组织均匀,使成形件的耐磨性和外观都有所改善;然而过量Y₂O₃的加入使得组织粗化,耐磨性降低,成形件翘曲,有裂纹出现。确定激光快速成形专用铁基粉末的成分。并研究了激光快速专用铁基粉末的成形件的组织特点及力学性能:1)激光快速成形件硬度达到32HRC以上。2)激光快速成形件磨损试验:成形件磨损失重为116.5mg,基体磨损失重为3802.9mg,激光成形件的耐磨性比基体提高了近33倍。3)激光快速成形拉伸件的抗拉强度为675MPa。4)无任何预热和缓冷处理的条件下在45钢基体表面进行激光快速成形,最后得到壁厚2mm,高40mm,外圆直径30mm的圆筒,圆筒上平面平整,下平面与基体结合良好,无翘曲现象。本文还用铁基合金与（TiO₂+C）反应体系,激光熔覆生成TiC原位增强铁基合金涂层。用X-射线衍射、SEM、EPMA测试方法研究了熔覆层的相组成、显微组织,结果表明:均匀分布的TiC颗粒可以通过原位反应生成,TiC的生成使得熔覆层的硬度较基体有很大程度的提高。更多还原

【Abstract】 Laser rapid forming（LRF）is a new and advanced manufacturing technology that has been developed on the basis of high power laser cladding technology and rapid prototyping.Most of the laser cladding and laser rapid forming materials are as the same of conventional applied techniques.In order to explore the potential application value of laser surface strengthening,new kind of cladding material needs to be developed.The processing research is the base of the laser cladding and rapid forming.First, we studied the effects of laser processing parameters such as laser power,scan speed, track overlap,Z axis increment,powder sending rate on the dimension and quality of forming samples.The optimal technologic parameters were powder sending rate: 10g/min;laser power:1400-1500W;scan velocity:5mm/s;spot diameter:3mm; overlap rate:50%;Z axis increment:0.3mm.Secondly,according to the forming materials design principle and the characteristic of materials used as laser cladding on the market,we confirmed the constitutes of the forming materials by and large.The effects of Y₂O₃ on microstructure,phase,wear-resistance of the laser cladding and rapid forming parts were also studied.The study shows that Y₂O₃ can make the microstructure finer,more uniform,improving the wear-resistance and appearance;but the excessive addition of Y₂O₃ can make microstructure coarser,reduce the wear-resistance and cause the prototyping part to warp and crack.And we confirmed the constitutes of the laser rapid forming materials.In the end,we studied the technic guideline of Fe-based powders alloy for the laser cladding and the laser rapid forming:First,the hardness of the cladding layers could surpass HRC32.Second,using tribological wear experiment machine,it has been found that the mass loss of the laser rapid forming part and the substrate is 116.5mg and 3802.9mg respectively.The wear-resistance of the laser rapid forming part is higher than that of the substrate.Third,the ultimate strength of laser rapid forming part is 675MPa.The end,without any preheating and slow cooling,a cylinder of laser rapid prototyping（wall thickness 2mm,height 40mm,outside diameter 30mm）can be made with a smooth surface and without gas holes and crack.In situ synthesized TiC reinforced Fe based coating was fabricated by laser cladding on steel substrate using Fe-based alloy and TiO₂+C as the precursor powders. The phase composition and microstructure of the clad layer were investigated by means of X-ray diffraction analysis（XRD）,scanning electron microscopy（SEM）and electron probe microanalysis（EPMA）.Results showed that uniformly distributed TiC particles could be synthesized by the in situ reaction.The hardness and wear properties of the clad layer were greatly improved due to the presence of TiC particles in comparison with the substrate.更多还原