用于激光熔敷的同轴送粉喷嘴的设计

为了克服目前用于激光熔敷的侧向送粉的不足，设计并试制了激光熔敷加工中使用的同轴送粉喷嘴．设计根据熔敷中使用的聚焦光束的特点，以一定假设为基础，从理论上对粉粒与管壁碰撞后的速度及运动轨迹进行了计算．结合计算所得的数据试制了同轴送粉喷嘴，并进行了试样加工，效果良好．     

送粉激光熔敷耐磨涂层制备工艺与组织结构

采用20%WC作为镍基自熔合金的掺杂增强相，研究了该复合材料在送粉激光熔敷工艺条件下的熔敷层显微组织、显微硬度与熔敷工艺规范间关系，得出了在实验条件下的优化工艺参数：激光功率为2．5kW(光斑离焦量60mm)；扫描速度为2．4mm／s；送粉量为3．0g／min．     

激光快速成型送粉器及其特性

针对激光快速成型送粉器进行了研究,讨论了激光快速成型技术和工艺中所要涉及到的关键问题,指出送粉器的送粉特性对激光快速成型质量会产生决定性的影响. 以现有的6种送粉器为例,详细说明了送粉器的几种典型送粉原理. 最后列表分析了此类送粉器在原理、特性及应用上的异同. 分析结果表明:需要研制小载流气体流量(<1L/min)、能输送更小颗粒粉末(尺寸<1m)的送粉器,例如纳米相级送粉,并对送粉原理进行进一步改进.     

激光熔敷镍基自熔性合金粉末的研制

针对激光熔敷表面处理技术对合金粉末材料性能的要求，分别研究了合金粉末的B含量、Si含量以及B、Si含量配比对激光熔敷的工艺性能、粉末形貌及涂层性能的影响，研制出具有良好的工艺性能和使用性能的激光熔敷用镍基自熔性合金粉末．     

激光熔覆快速成形光内送粉方式的研究

针对目前激光熔覆快速成形所采用的单粉管光外侧向送粉和多粉管光外侧向同轴送粉两种方式的不足,介绍了光内同轴送粉工艺下的激光束与粉末相互作用过程.     

FeCrSiB合金的激光熔敷

应用千瓦级 CO_2激光器对 A_3钢上的 Fe 基热喷涂层进行熔敷处理,用金相、x 射线衍射、扫描电镜、透射电镜、硬度、磨损、声发射及电化学等方法研究了熔敷层的组织与性能。结果表明:激光熔敷消除了热喷涂层的不致密性缺陷,使涂层与基材实现冶金结合。激光熔层组织显著细化,成分均匀,消除了大块碳化物偏析,呈现尺寸1～2 μm 的胞状晶快冷组织。其相组成为α′-Fe+γ-Fe+M_7C_3+M_(23)C_6+F_2B。激光熔敷产生的多种强化机制使涂层的硬度、耐磨性、脆性、强度及耐腐蚀性有了显著提高,从而在低廉的钢材上获得性能优异的表面。是一种有实用价值的激光熔敷技术。     

激光熔敷Ni基合金组织与物相的研究

用ＳＥＭ，ＥＤＡＸ和ＸＲＤ等方法研究了激光快速熔凝Ｎｉ基合金的组织与物相。结果表明合金中的细枝晶是由γ＇相和与之共存的γ相组成的，枝晶间共晶中第二相应为Ｎｉ３１Ｓｉ１２．     

激光熔敷钻基合金高温腐蚀的试验研究

本文对以2Cr13不锈钢为基础，表面经激光熔敷钴基金合金在高温PbSO4盐中的热腐蚀行为和机制，进行了深入的研究探讨。试验结果表明，经激光敷估基金合金，耐高温腐蚀性比原2Cr13钢提高2．5倍以上；耐磨性提高2倍以上。原因是获得细密枝晶＋多元共晶组织，大量Co能促进Cr2O3、CoO.Cr2O3致密保护膜的形成，阻碍S的扩散，因而提高了耐高温腐蚀性能。腐蚀机制是沿晶腐蚀，硫化一氧化循环进行造成剥落型破坏腐蚀。     

Nd:YAG激光和CO2激光熔敷性能比较研究

从Maxwell方程和Hagen-Ruben公式出发,计算了Nd：YAG激光(波长为1．06μm)和CO2激光(波长为10．6μm)在金属中的吸收率和穿透深度,并做了Nd：YAG激光与CO2激光的熔敷试验比较．结果表明：Nd：YAG激光在金属中吸收率约为CO2激光的3倍,更适于激光熔敷;CO2激光在金属中穿透力约为Nd：YAG激光的3倍,更适于激光相变淬火．     

Effects of Powder Feeding Rate on Interaction between Laser Beam and Powder Streamin Laser Cladding Process

A theoretical model was presented to calculate the laser intensity distribution and the particle temperatures at different sites of the workpiece in the laser cladding process By using this model, the effects of the powder feeding rate on the laser intensity distribution and the particle temperatures were inrestigated ,the caleuluted results under the condition of different injection angles were also plotted it is shout that with increasing the injection angle,the laser inuensity distributwons are similar but the peak ralue of the laser intensity decreases simdlaneously the peak ralue of the particle tenperature increases and the disribution of the particle temperatures gets central symmetrical gradually.these tests reslts should be considered in model of laser cladding due to their sub the effects on the dynamic processes in laser molten pool.     

Investigation on laser cladding of MoSi2 powder on steel

The feasibility of the fabrication of coatings for elevated-temperature structural applications by laser cladding MoSi2 pow- der on steel was investigated. A dense and crack-free fine coating, well-bonded with the substrate has been obtained by this technique This coating consists of FeMoSi, Fe2Si and a small amount of MosSi3 due to dilution of the substrate in the coating. The microstructure of the coating is characterized of typical fine dendrites, The dendrites are composed of FeMoSi primary phase, and the interdendritic areas are two eutectic phases of FeMoSi and Fe2Si. The hardness of the coating reaches 845 Hv0.5, 3.7 times larger than that of the steel substrate （180 Hv05）.     

3-D transient numerical simulation on the process of laser cladding by powder feeding

A 3-D transient mathematical model for laser cladding by powder feeding was developed to examine the macroscopic heat and momentum transport during the process, based on which a novel method for determining the configuration and thickness of cladding layer was presented. By using Lambert-Beer theorem and Mie‘s theory, the interaction between powder stream and laser beam was treated to evoke their subtle effects on heat transfer and fluid flow in laser molten pool. The numerical study was performed in a co-ordinate system moving with the laser at a constant scanning speed. A fixed grid enthalpy-porosity approach was used,which predicted the evolutionary development of the laser molten pool. The commercial software PHOENICS, to which several modules were appended, was used to accomplish the simulation. The results obtained by the simulation were coincident with those measured in experiment basically.     

激光熔覆成形技术的研究进展

为了应用能量守恒对同轴送粉激光熔覆中的熔覆层性能进行精确计算,研究了激光束穿过粉末云时能量的衰减现象和衰减规律. 利用流体软件模拟实际喷嘴喷粉的过程,并利用有限元软件模拟激光束穿过粉末云的能量衰减规律,得到了激光-粉末相互作用区域内粉末云质量浓度随\t\t\t\t\tz轴的分布曲线,以及不同激光功率下和不同粉末云质量浓度下,从喷嘴出口到基材之间粉末云对激光衰减率的变化曲线. 结果表明:激光束穿过粉末云的过程中,未到粉末交汇处时光强衰减较弱,汇聚处能量衰减明显. 对衰减率进行定量研究可以很好地用于熔池温度场的精确计算.\t\t\t\t

     

激光熔覆纳米Al2O3的粉末冶金件的表面组织

运用纳米Al2O3作为粉末冶金件的表面改性材料,通过激光熔覆试验对粉末冶金件进行了表面改性。分析了激光熔覆的凝固过程,运用金相显微镜和扫描电镜对粉末冶金材料的表面改性层组织进行了观察,并对改性层不同组织的形成因素进行了研究。结果表明:熔覆后材料组织分为熔覆层区、界面结合区、基体区。从熔覆层到基体密度呈现由密向疏变化。激光熔覆组织主要受涂层成分及含量、工艺参数、形状控制因子G/υ(温度梯度/凝固速度)的影响,而形状控制因子又决定于工艺参数。当光带矩形光斑尺寸为15mm×2mm时,最佳功率为2.5kW,最佳扫描速度为90mm/min。     

新型龙门式高速加工中心直线进给单元设计

高速加工的出现引起了机床结构与传动的重大变革，传统龙门式机床已很难适应高速加工发展的需要。对新、老龙门式加工中心的结构进行了分析比较，并结合正在开发研制的新型墙式龙门高速加工中心，对直线进给单元的基本类型和直线电机的结构布局进行了分析，研究了直线进给单元的基本结构。