基于RSM的激光增材制造316L不锈钢尺寸精度研究

为了实现选区激光熔化成形精度工艺参数的优化,采用响应面法对选区激光熔化316L不锈钢的成形尺寸精度进行研究。结果表明,响应面模型的预测值与试验值具有良好的相关性,激光功率和扫描速度对尺寸精度具有显著的影响,且随着激光功率的增大和扫描速度的减小其成形的尺寸绝对误差越大,对选区激光熔化成形尺寸精度的控制具有重要意义。     

金属构件选区激光熔化快速成型铺粉控制系统研究

选区激光熔化（SLM,Selective Laser Mching)技术是直接将选区内金属或合金粉末逐层熔化,堆积成一个冶金结合,组织致密的实体,其外形不需进一步加工,经抛光或简单表面处理可直接作模具。本文是在自行研制的国内首台金属构件直接选区激光熔化实验样机设备基础上,介绍分析了该设备的控制系统,重点介绍了选区激光熔化设备铺粉控制系统,它是该技术能否达到预期目标的关键因素之一,并且对其铺粉精度进行了试验验证,为金属构件直接选区激光熔化成型工艺研究奠定了基础。     

基于Matlab GUI框架下激光选区熔化成形铺粉质量检测系统研究

在激光选区熔化成形设备铺粉过程中,存在刮刀条纹、刮刀撞击、铺粉不完全、超高角和碎屑5种铺粉缺陷。为了实现激光选区熔化成形铺粉质量的在线和离线检测,基于Matlab GUI软件设计了一个激光选区熔化成形铺粉质量检测系统。利用Matlab图像捕获工具箱实现图像的实时采集,或将已采集的铺粉图像进行单张或批量质量检测,提取铺粉缺陷特征并显示结果、缺陷位置和运行时间;铺粉质量检测结果可保存为.txt文件,方便操作人员对激光选区熔化零件成形质量分析。系统对人工智能在灰度粉末铺层表面的均匀性进行了有益的探索,利用计算机图像识别技术代替人眼,判断激光选区熔化成形铺粉表面缺陷,为激光选区熔化成形铺粉质量分析提供了一个强有力的工具。     

多激光束选区熔化成形技术研究

多激光束选区熔化技术可以改善单激光束选区熔化成形过程中产生的球化、翘曲变形及裂纹等缺陷。研究了多激光束选区熔化成形系统中涉及的多个关键系统,包括铺粉与送粉系统、双激光光路系统、控制系统及分层切片数据处理软件系统等,并进行大量设备验证性工艺试验研究,成功研发出多激光束选区熔化成形设备,并成形出性能优异的复杂精密金属构件。     

选区激光熔化工艺参数对燃料电池316L不锈钢双极板性能的影响

316L不锈钢材料具有耐蚀性好、成形性好、成本低等优点,在燃料电池金属双极板领域有着良好的应用前景.基于传统等材、减材加工方法难以成形复杂结构燃料电池双极板的瓶颈,使用选区激光熔化技术可实现复杂结构316L不锈钢双极板的成形制造.针对燃料电池不锈钢金属双极板的应用背景,系统研究了不同激光工艺参数(激光功率、激光扫描速度)对所成形316L不锈钢材料微观组织及双极板所需耐蚀性和表面接触电阻的影响,并对比了传统锻造316L不锈钢与选区激光熔化316L不锈钢在显微组织和性能上的差异.结果 表明,选区激光熔化成形316L不锈钢的致密度随着激光功率的增大而增大,随着扫描速度的增大而减少,并在激光功率为300W,扫描速度为1500～2000 mm/s时达到最大值.相比于具有等轴晶特征的锻造不锈钢试样,选区激光熔化成形不锈钢试样柱状晶组织有利于降低晶界对电流的阻碍作用,从而降低了表面接触电阻;同时,随着样品表面粗糙度的提高,选区激光熔化成形不锈钢试样的表面接触电阻降低.致密度高的选区激光熔化成形不锈钢试样的耐蚀性优于锻造成形不锈钢试样,且随着致密度的减小,选区激光熔化成形试样的耐蚀性逐渐降低.本研究结果表明选区激光熔化成形316L不锈钢材料可用于燃料电池金属双极板.     

选区激光熔化快速成型系统及工艺研究

选区激光熔化技术是近几年出现的能直接制造终端、近终端金属产品的快速成型技术.描述了选区激光熔化快速成型设备系统组成,选区激光熔化对激光子系统、扫描子系统及软件子系统的功能要求.经工艺实验,分析了扫描速度、激光功率、扫描间距对成型质量的影响,并通过成型1个三维金属实体,验证了系统的可行性.     

激光能量密度对SLM成形316L不锈钢表面完整性的影响

采用激光选区熔化(Selective Laser Melting, SLM)技术成形制备316L不锈钢试样,探索了不同激光能量密度对金属增材制造成形质量的影响规律。选取激光功率、扫描间距、扫描速度和铺粉厚度等工艺参数,设计了正交试验,分析了激光能量密度对试件侧表面的表面粗糙度、维氏硬度、致密度、残余应力及表面形貌的影响规律。结果表明,随着激光能量密度的增大,试件侧表面的表面粗糙度与维氏硬度呈现先减小后增大的趋势,致密度和残余应力呈现先增大后减小的趋势,在激光能量密度为70.37 J/mm³时试件表面质量最佳,即最优工艺参数为激光功率P=190 W,扫描速度v=750 mm/s,铺粉厚度h=0.03 mm,扫描间距d=0.12 mm。     

基于激光选区熔化的免组装机构直接制造技术

采用数字化设计和组装并直接制造成形、无需实际组装工序的机构,称之为免组装机构。激光选区熔化能够直接制造冶金结合、组织致密、尺寸精度高和良好力学性能的功能零件,是直接制造免组装机构的理想技术。研究了激光选区熔化成形免组装机构的摆放方式、间隙特征的尺寸精度和表面粗糙度、间隙特征结构优化等关键技术。通过自由设计和DiMetal-100系列激光选区熔化成形设备成形了免组装的铜钱算盘和折叠算盘、平面连杆机构(曲柄滑块、曲柄摇杆、摇杆滑块)和万向节等免组装机构。研究证明,激光选区熔化不仅能够顺利成形形状很复杂的零件,也能够直接成形具有相对运动的免组装机构,为机电产品的数字化设计和一体化制造提供了一种可行的方法。     

大型金属构件激光选区熔化成形设备设计

激光选区熔化成形技术发展迅速,用于大尺寸复杂金属构件整体成形的激光选区熔化成形设备的需求增加,其结构形式的选择需要结合大尺寸零件及成形基板的装卸以及激光选区熔化成形技术的工艺特性综合考虑。阐述了一种大型金属构件激光选区熔化成形设备的设计思路,提出了该设备的结构方案,叙述了该设备结构的各功能部件组成及设计要点。     

电子束选区熔化技术中可控振动落粉铺粉系统的研究

分析了快速成形技术中常用供粉系统与铺粉系统的优缺点。结合电子束选区熔化成形技术在真空环境下人工无法干预、成形区域温度高、成形件刚度大等特点和接触式铺粉机构遇到凸起后经常无法越过而导致成形中断的实验情况,提出了一种可控振动落粉铺粉方案。设计了具有粉末结拱与振动破拱功能且不与成形件相接触的上置式铺粉筛及具有称重传感器反馈的铺粉系统,通过改变铺粉筛的运行速度和加速度实现粉末铺送功能。实验结果表明,该系统运行可靠,在铺粉筛中粉末量一定的情况下可实现均匀铺粉,铺粉厚度通过改变铺粉筛运行速度和加速度来获取,最小粉末层厚度可达0.1mm。     

选区激光熔化工艺参数对Ti6Al4V粉末成型性的影响

以Ti6Al4V钛合金粉末为研究对象,在单层扫描和单道扫描实验的基础上,研究SLM工艺参数对Ti6Al4V合金材料成型性的影响,并进行了块体成型实验,通过设计正交试验及观察试样的形貌和致密度分析,最终得到Ti6Al4V合金粉末SLM块体成型的最佳工艺参数为:激光功率400W、搭接率1、扫描速度750mm/min,其致密度可以达到96.17％.     

Research on the fabricating quality optimization of the overhanging surface in SLM process

Overhanging surface is inherent geometric restraint during selective laser melting (SLM), which is suitable for various complex parts fabrication. In order to improve the fabricating quality of overhanging surface, a series of experiments were designed to investigate the effects of inclined angle, scanning speed, laser power, accumulated residual stress, and scanning vector length on overhanging surface fabrication. Analysis found that overhanging surface would warp easier when the inclined angle and the scanning speed became smaller and the warping trend will be larger as the laser power became larger. The relationships of laser power, scanning speed, and the critical inclined angle were mutual restraint, that is, larger inclined angle will be designed when the laser power becomes larger and scanning speed gets smaller, or vice versa: the selection of the fabricating parameters will be determined by established inclined angle of the overhanging surface. More serious warp would happen as the processing layers increased as a result of residual stress accumulation, and it was found that longer scanning vector were more helpful to stress accumulation, leading to more serious warp than shorter vector. At last, two effective methods were adopted to optimize overhanging surface fabrication, including adjusting part orientation to improve the inclined angle at the key position, and controlling regional parameters to reduce energy input. Above two ways were adopted to manufacture complex parts with typical overhanging surface, the results proved that adjusting part orientation and controlling regional parameters were effective ways to improve the fabricating quality of overhanging surface. In this study, the basis for building overhanging surface by SLM was provided from the view of process and design, and the preliminary solutions were proposed to manufacture complex metal parts with lower risk.     

选区激光熔化快速成型扫描路径优化算法研究

本文针对选区激光熔化成型过程中所存在的翘曲变形、球化等现象及其成因进行了简要分析,并且结合相关文献,提出了重复扫描和分区扫描相结台的路径生成算法.分区避免了长线扫描,因而可以有效减小翘曲变形,一个层面上重复扫描可以减小层间的内应力,并且可以提高熔化层的表面质量,因而此种扫描路径生成算法可以有效地改善零件的成型质量.     

激光选区熔化单道扫描与搭接数值模拟及试验

激光选区熔化(Selective laser melting, SLM)单道扫描的数值模拟,在数值建模时多采用规则实体模拟铺设的粉末层,通过等效定义材料热物理属性模拟铺设粉末层中粉末与气体共存的情况,难以模拟粉末颗粒的随机性而带来的扫描结果的随机性,且难以分析熔池形貌、内部缺陷的微观衍变过程。针对SLM成形过程中激光功率和单道搭接率对扫描单道和单道搭接质量的影响,以316L不锈钢材料为例,建立SLM首层单道扫描与单道搭接数值模拟模型。SLM的铺粉过程在基于离散单元法的EDEM中建立,并得到数值化的粉床几何模型。SLM的单道扫描与搭接的模拟基于有限体积法,在FLUENT中实现,采用两相流模型与熔化/凝固模型捕捉熔池形貌变化过程,得到不同激光功率和扫描搭接率下成形单道与单道搭接的数值模型。最后结合试验表明了在100～300 W激光功率下成形单道表面形貌与缺陷的形成,当激光功率为100～150 W时,单道形貌不规则,且容易形成局部缺陷;在200～300W功率下,激光功率越大,保证搭接质量的最低搭接率越小,当激光功率为250 W时,应保证单道填充间距不大于0.1 mm。研究成果对SLM工艺参数...     

数字孪生驱动的金属选择性激光熔融成形过程在线监控

由激光熔融过程的极热极冷特性造成的成形零件质量缺陷一直阻碍着选择性激光熔融技术的广泛应用,为制造出高质量的零件,提出一种数字孪生驱动的金属选择性激光熔融成形过程在线监控方法,应用该方法建立智能成形系统并进行案例分析.基于粉末熔融过程的物理和虚拟建模、过程在线监测和大数据分析,构建了包括设备层、数据转换层、网络层、控制层...     

Two-dimensional modeling of sintering of a powder layer on top of nonporous substrate

Selective laser sintering (SLS) of a two-component metal powder layer on the top of multiple sintered layers by a moving Gaussian laser beam is modeled. The loose metal powder layer is composed of a powder mixture with significantly different melting points. The physical model that accounts the shrinkage induced by melting is described by using a temperature-transforming model. The effects of the porosity and the thickness of the atop loose powder layer with different numbers of the existing sintered metal powder layers below on the sintering process are numerically investigated. The present work will provide a better understanding to simulate much more complicated three-dimensional SLS process.     

Select laser melting of W–Ni–Fe powders: simulation and experimental study

Using W, Ni, and Fe powders as raw materials, selective laser melting (SLM) technology was considered for fabrication of 90W–7Ni–3Fe parts in one step. The investigation into simulation of temperature field of SLM W–Ni–Fe powder system was highlighted. Effects of processing parameters of scan velocity, laser power, scan interval, and preheating process on temperature field distribution were studied through establishing a 3D model based on finite element analysis theory. The simulation results show that a lower thickness, narrower scan interval, and a slower scan velocity tend to improve the temperature in powder bed. Moreover, the parameter range in which the maximum temperature in powder bed could reach up to the melting point of W (about 3,420°C) was obtained. Experiments on different processing parameters were carried out, and a good agreement with the simulation results could be found.     

Two-dimensional modeling of sintering of a powder layer on top of nonporous substrate

Selective laser sintering (SLS) of a two-component metal powder layer on the top of multiple sintered layers by a moving Gaussian laser beam is modeled. The loose metal powder layer is composed of a powder mixture with significantly different melting points. The physical model that accounts the shrinkage induced by melting is described by using a temperature-transforming model. The effects of the porosity and the thickness of the atop loose powder layer with different numbers of the existing sintered metal powder layers below on the sintering process are numerically investigated. The present work will provide a better understanding to simulate much more complicated three-dimensional SLS process.     

The helix scan strategy applied to the selective laser melting

In selective laser melting processing, the residual stress will occur inside the melted layer inevitably, and the deformation will be made simultaneously. The laser scanning strategy determined the deformation magnitude and the shape residual stress profiles. In order to optimise the manufacture and reduce the deformation of manufactured metal layers, helix scan strategy and progressive scan strategy for selective laser melting technology have been developed. As a result, the helix scan strategy helps to decrease the deformation of melted layer more effectively.     

Balling behavior of stainless steel and nickel powder during selective laser melting process

Balling phenomenon, as a typical selective laser melting (SLM) defect, is detrimental to the forming quality. In this work, a detailed investigation into the balling behavior of selective laser melting of stainless steel and pure nickel powder was conducted. It was found that the SLM balling phenomenon can be divided into two types generally: the ellipsoidal balls with dimension of about 500?μm and the spherical balls with dimension of about 10?μm. The former is caused by worsened wetting ability and detrimental to SLM quality; the latter has no obvious detriment to SLM quality. The oxygen content plays an important role in determining the balling initiation, which can be considerably lessened by decreasing the oxygen content of atmosphere to 0.1%. A high laser line energy density, which can be obtained by applying high laser power and low scan speed, could enable a well-wetting characteristic. The effect of scan interval on balling initiation is not obvious as long as the scan track is continuous. The surface remelting procedure can also alleviate the balling effect in a certain extent, due to the melting and wetting of metal balls. Moreover, the balling phenomenon of pure nickel was also studied, and the results implied that the balling discipline had a universality.