Laser welding of superalloy K418 to 42CrMo steel

进行了K418高温合金和42CrMo钢的激光焊接实验，分别采用OM、SEM、XRD和EDS等手段分析了焊缝的金相组织和物相组成，评价了焊缝的显微硬度和拉伸强度。结果表明：焊缝主要由树枝状非平衡凝固的FeCrNiC（力固溶体组成，此外，还有少量细小、弥散的Ni_3Al（γ′）相、Laves颗粒和少量MC碳化物分布在树枝晶间区域。由于主要强化相γ′在激光辐照后的部分溶解和随后快速凝固的抑制作用，焊缝的硬度虽分布较均匀但低于母材。由于没有获得穿透的焊接接头，焊接接头的强度约只有母材的88．5％，焊缝的断裂机制是塑性和脆性断裂的混合机制。由于在焊缝中存在一些Laves颗粒，这促进了微裂纹和微孔的形成和扩展，降低了焊接接头的抗拉强度

Intensity Distribution Design for Laser-Induced Thermal Loading Based on Numerical Simulation

To accomplish laser-induced thermal loading simulation tests for pistons,the Gaussian beam was modulated into multi-circular beam with specific intensity distribution.A reverse method was proposed to design the intensity distribution for the laser-induced thermal loading based on finite element(FE) analysis.Firstly,the FE model is improved by alternating parameters of boundary conditions and thermal-physical properties of piston material in a reasonable range,therefore it can simulate the experimental resul..

宽带激光熔覆送粉喷嘴的结构设计与粉末流场研究

设计一种新型的送粉喷嘴结构,适用于宽带激光熔覆和增材制造。该结构使用多通道出口有效降低粉末流在扫描方向的发散角,通过添加内部整流圆柱调整粉末流在垂直扫描方向上的浓度分布。采用离散相模型,研究该喷嘴结构输出的粉末流场。优化分流圆柱的尺寸,使该送粉喷嘴能够输出浓度分布均匀的宽带粉末流,并沉积出厚度均匀的宽带涂层

Numerical simulation of thermal behavior and multicomponent mass transfer in direct laser deposition of Co-base alloy on steel

During direct laser deposition process, rapid melting-solidification and addition of multicomponent powder lead to complex transport phenomena in the melt pool. The thermal behavior and mass transport significantly affect the solidified microstructure and properties of fabricated layer. In this paper, an improved 3D numerical model is proposed to simulate the heat transfer, fluid flow, solidification and multicomponent mass transport in direct laser deposition of Co-base alloy on steel. The solidification characteristics, including temperature gradient (G), solidification growth rate (R) and cooing rate (G x R), can be obtained by transient thermal distribution to predict the morphology and scale of the solidification microstructure. Multicomponent transport equation based on a mixture-averaged approach is combined with other conservation equations. The calculated melt pool geometry and the composition profiles of iron (Fe), carbon (C), cobalt (Co) and chromium (Cr) are compared with the experimental results. The results show that in the initial stage of direct laser deposition, the rapidly mixture of substrate material and added material occur in the melt pool and conduct plays an important role in heat transfer due to the low Peclet number. As the melt pool is developed, the heat and mass transfer in the melt pool are dominated by strong Marangoni convection. An unmixed zone is observed near the bottom of melt pool where the convection is frictionally dissipated due to the presence of solidified dendrites. Since the G/R decreases and G x R increases from the bottom to the top of the solidified track, the morphology of the microstructure changes from planar front to columnar dendrites to equiaxed dendrites and the grain size decreases. (C) 2016 Elsevier Ltd. All rights reserved

射频激励快速轴流一氧化碳激光器

一种横向射频激励快速轴流CO激光系统，由激光谐振腔和气体循环系统构成，谐振腔包括放电管、中心部件，射频电极和端部件，端部件内设有相应的反射镜；气体循环系统包括涡流泵和气流通道，气流通道上设有热交换器。工作气体是由放电管间的中心部件流入，从两端部件流出，射频电极与放电管管壁间具有一倾角，放电管的端口采用卷边形式，设置在涡流泵与中心部件间的为二级热交换器，用以将气体温度降至足够低，以便系统功能得到发挥

一种铜铬合金触头的激光表面改性方法

本发明提供了一种铜铬合金触头的激光表面改性方法，包括如下步骤：步骤100，将待加工的铜铬合金触头放置在可控氧含量的操作室内，并利用控温夹具将所述铜铬合金触头固定住；步骤200，根据对所述铜铬合金触头的改性要求，选择使用的激光类型并调整激光的加工参数；步骤300，控制激光沿规定的路线对所述铜铬合金触头的表面进行逐步且全面的加工，得到在表面形成10～300μm细晶层的铜铬合金触头，在所述细晶层中，铬颗粒的粒度小于1μm。本发明的方法对基体产生的热影响小，除了提高屈服强度、拉伸强度和硬度等机械性能外，还可能够在铜铬合金触头的表面形成更致密的细晶层，大大降低触头表面的粗糙度，提高铜铬合金触头的电学性能和分断电流能力

一种调整铜铬合金触头表面激光改性时运动轨迹的方法

本发明提供了一种调整铜铬合金触头表面激光改性时运动轨迹的方法，包括：步骤100，获取待加工铜铬合金触头的几何形状、尺寸和改性后的性能要求，以及激光改性时的参数；步骤200，利用上述信息，通过数值计算建立仿真模型，得到优化后的符合当前铜铬合金触头激光改性的轨迹运行模型；步骤300，根据轨迹运行模型给出的运行路线并按预定的激光加工参数，对铜铬合金触头进行表面激光改性。本发明的方法可以在激光改性时，使激光在达到改性目的的同时，提高熔池的冷却和移动速度，有效地降低热应力并且降低热应力变化幅度，使激光的能量均匀地作用于铜铬合金触头的表面，降低铜粗糙度和提高平整度，并形成均匀的高性能铜铬合金触头表面细晶层

Digitized Processing Track Generation of a Computer Integrated Multi-Functional 5-Axis Laser Processing System

Based on the computer integrated and flexible laser processing system, an intelligent measuring sub-system was developed. A novel model has been built up to compensate the deviations of the main frame-structure, and a new 3-D laser tracker system is applied to adjust the accuracy of the system. To analyze the characteristic of all kind surfaces of automobile outer penal moulds and dies, classification of types of the surface、brim and ridge(or vale) area to be measured and processed has been established, resulting in one of the main processing functions of the laser processing system. According to different type of surfaces, a 2-D adaptive measuring method based on B?zier curve was developed; furthermore a 3-D adaptive measuring method based on Spline curve was also developed. According to the laser materials processing characteristics and data characteristics, necessary methods have been developed to generate processing tracks, they are explained in details. Measuring experiments and laser processing experiments were carried out to testify the above mentioned methods, which have been applied in the computer integrated and flexible laser processing system developed by the Institute of Mechanics, CAS