氧化锆零件激光选区烧结/冷等静压复合成形技术

氧化锆陶瓷材料以其优异的性能在工业生产中具有极大的应用前景,但由于脆性大、硬度高等原因,复杂形状氧化锆零件往往难以成形和加工。为了获得复杂形状氧化锆陶瓷零件,通过溶剂沉淀法将粘接剂尼龙12覆膜至纳米氧化锆粉末的表面,然后对覆膜后的粉体进行激光选区烧结(Selective laser sintering, SLS)成形,并通过传统的冷等静压(Cold isostatic pressing, CIP)技术对SLS零件进行致密化处理,同时满足氧化锆初坯成形时形状复杂度和密度的要求。通过试验得出在激光能量密度为0.415 J/mm2时,获得的SLS陶瓷件密度较大,对不同激光能量密度制备的SLS陶瓷件进行保压压力为200 MPa的冷等静压致密化处理,根据热脱脂机理以及粘接剂的TG曲线,分别制定了SLS/CIP试样的热脱脂工艺,最后对脱脂试样进行高温烧结,在后续处理的各环节,氧化锆零件的密度仍受SLS成形的影响,但该影响逐渐减弱,SLS/CIP/FS成形件最大相对密度和维氏硬度分别达到了97%和1180 HV1,已接近“模压-烧结”的致密氧化锆陶瓷的性能,在试样断口的扫描电子显微镜(SEM)分析基础上,对氧化锆复合成形的微观演变进行了研究。虽然最终烧结件密度和硬度仍有待提高,但是提出了一种极具潜力的氧化锆零件近净成形工艺方法,为制造高性能复杂形状的陶瓷零件奠定了基础。     

激光烧结复合尼龙材料的工艺参数优化研究

研究在选择性激光烧结（SLS）过程中,复合尼龙粉末激光烧结工艺参数的优化.讨论激光功率、预热温度、扫描速度、铺粉厚度等工艺参数对制件强度的影响.采用正交试验的方法,在不同工艺参数下将复合尼龙粉末烧结成9组哑铃状试样,以强度为指标,计算出强度最好的工艺参数组合,并结合比较试件的尺寸精度得到激光烧结复合尼龙材料的最优工艺参数为：激光功率14 W,预热温度95℃,扫描速度1 400 mm/s,铺粉厚度0.1 mm.     

激光选区烧结及其在精密制造业中的应用

研究了快速、精确制造金属模具的方法,提出利用激光选区烧结(SLS)技术来快速制造高精度陶瓷型精密铸造用母模.首先,采用正交试验法研究了激光选区烧结工艺参数对制件精度的影响,确定了最佳激光烧结工艺.在此基础上利用浸水起模法替代传统的起模喷烧工艺对陶瓷型精密铸造工艺进行改进.结果表明,选定激光烧结工艺参数为激光功率25 W,扫描速度2.0 m/s,扫描间距0.19 mm,分层厚度0.25 mm时,试样尺寸收缩率最低可达2％.采用陶瓷型浸水起模法起模容易,起模后陶瓷型表面光洁,在200℃焙烧温度下抗弯强度较高,为0.361 MPa.这些结果表明,利用SLS技术能够快速、准确地制造出陶瓷型精密铸造所需母模.     

激光选区烧结超高分子量聚乙烯工艺及性能

研究了激光选区烧结(SLS)成型工艺中不同工艺参数以及后续热处理工艺对超高分子量聚乙烯(UHMWPE)材料成型性能的影响。通过调整扫描间距、激光功率、扫描速度等不同工艺参数,描述了SLS成型UHMWPE零件的致密度、拉伸强度以及断裂伸长率,并对热处理前后的SLS成型UHMWPE零件的力学性能进行了比较。结果显示,致密度、拉伸强度、断裂伸长率总体上与激光功率呈正相关关系,与扫描间距、扫描速度呈负相关关系。经热处理后,SLS成型UHMWPE零件的力学性能有明显提高,致密度达到95.12%,抗拉强度达到24.08 MPa,断裂伸长率达到334.82 MPa。实验结果表明:SLS成型UHMWPE零件与模塑成型UHMWPE零件性能尚有差距,仅优化成型工艺不足以得到理想性能,但经热处理后,零件性能基本满足使用要求。     

SLS烧结实验的优化设计

激光功率、扫描速度、铺粉厚度、预热温度及扫描间距是影响SLS成型质量的主要因素.通过激光快速成型机AFS-450制作专门的样件,采用正交试验和方差分析,对SIS成型工艺参数进行优化设计.确定了ABS粉末最佳的烧结参数,即预热温度为100℃、扫描速度为2000mm/s、激光功率为24W、铺粉厚度为0.2mm.     

喷雾造粒技术在反应烧结SiC密封材料中的应用研究

研究了水基料浆喷雾造粒粉体在反应烧结SiC密封材料中的应用.通过对均匀、稳定分散的水基SiC C料浆进行喷雾干燥,制备的反应烧结碳化硅复合粉体与传统工艺相比流动性能得到明显改善,适用于连续自动干压成型,并且避免了传统工艺的热压成型.采用新工艺制备出密度为3.10 g/cm3,游离硅含量为8.22Wt%,硬度(HRA)90,抗折强度为434MPa的碳化硅密封材料,主要性能高于传统工艺和行业标准,可以与国外同类产品技术指标相比.     

粉末薄层选区激光烧结温度场数值模拟与实验研究

单层粉末的激光烧结温度场对三维结构熔结成型有着直接影响。通过对工程塑料粉末选区激光烧结过程能量作用形式的分析,构建了粉体与金属基板界面接触热阻的导热模型和扫描烧结的移动热源模型;利用有限元法对功率为10～25W,光斑直径为0.24mm的激光逐行扫描烧结过程的温度场进行了数值模拟;通过温度场分布模拟和激光烧结实验得到了单层厚度为0.5mm的PA6粉末行扫描间距的优化区间为0.3～0.4mm,获得了熔结质量较好、厚度均匀的平板形烧结物,为进一步优化工艺参数提供了基础。     

选择性激光烧结激光能量密度与温度补偿规律研究

选择性激光烧结（SLS）成型预热温度从成型缸中间到缸壁呈降低趋势,由于预热温度不均匀,导致SLS成型件密度不均匀。针对这一问题,通过增加激光能量密度对预热温度不足进行了补偿。通过试验建立了激光能量密度差△E与预热温差△T的经验公式,并比较了温度补偿前后烧结件的机械强度。实验结果表明,通过增加激光能量密度对预热温度不足进行补偿,提高了产品机械强度。     

铜基金属粉末直接激光烧结工艺及成形件显微组织研究

对多组分铜基金属粉末(组分包括Cu、Cu-10Sn、Cu-8.4P)进行了直接激光烧结实验。优化激光功率和扫描速率,以实现粉末部分熔化状态下的液相烧结,其中Cu作为结构金属,Cu-10Sn作为粘结金属,而P元素则作为脱氧剂。激光烧结直接成形了尺寸为210mm×70mm×9mm的复杂形状铜基金属零件,在零件底部设置了预烧结层,以保证良好的激光烧结过程及成形精度。烧结致密度达理论密度的94.7%,而最大尺寸误差仅为0.78%。     

选择性激光烧结陶瓷粉末机理初探

综述了烧结过程、烧结原动力,研究了选区激光烧结复合陶瓷粉末的烧结性能。结果表明,通过合理控制激光工艺参数（特别是激光功率和扫描速度）,能顺利实现粉末烧结成形,且无明显的“球化”效应和翘曲变形。扫描电镜分析证实,此复合粉末体系的激光烧结是基于液相烧结机制,表面自由能的改变是其烧结的原动力。     

聚乳酸/羟基磷灰石复合材料激光选区烧结工艺优化与性能研究

以生物可降解材料聚乳酸（PLA）和生物骨基质的主要无机成分羟基磷灰石（HA）为研究对象。为获得复合材料激光选区烧结(SLS)制件的最佳成形参数，首先对纯PLA的SLS工艺进行了优化，发现最优的激光能量密度范围为0.040~0.075 J/mm2，且制得的纯PLA试样的拉伸强度均超过23 MPa，最高可达27.28 MPa。为研究HA含量对PLA/HA复合材料微观结构与力学性能的影响，以激光能量密度为0.040 J/mm2（激光功率12 W,扫描速度1 500 mm/s）对不同HA含量的PLA/HA复合材料进行了成形。实验结果表明，当HA质量分数为10%时，PLA/HA复合材料的力学性能和微观形貌最优。水接触角测试显示材料的接触角从69.52°降至57.96°，表明材料的亲水性能得到了改善。     

Densification of alumina components via indirect selective laser sintering combined with isostatic pressing

To improve the final density of ceramic parts via indirect selective laser sintering (SLS), cold/hot isostatic pressing (CIP/HIP) technologies were introduced into the process. The proposed approach in the present study combined spray drying with mechanical mixing by which we prepared a kind of compound powder consisting of polyvinyl alcohol (PVA, 1.5 wt%), epoxy resin E06 (8 wt%), and alumina so as to get a good fluidity for SLS. At the first step, SLS parts reached the highest relative density of about 32 % when the laser energy density was 0.094 J/mm², which facilitated the next operation and improvement of final density. Then, a soft polymer canning was prepared for CIP around the surface of SLS alumina ceramic parts using pre-vulcanized natural rubber latex RTV-2, gelation and film. Following that, we experimented on different CIP maximum pressure which had different effects on densification of SLS alumina parts, the whole process in CIP was divided into three stages of I, II, and III. Based on thermal gravity curve of epoxy resin E06, ignoring the impacts of the only 1.5 wt% PVA on degreasing, green bodies were degreased and furnace-sintered. Finally, the relative density of alumina parts reached 95.94 % after HIP process. Field emission scanning electron microscopy was used to analyze the densification evolvement in each stage of process and the fracture mechanism. The study showed a positive and practical approach to manufacture ceramic matrix and ceramic components with complex shape by indirect SLS technology.     

复杂刃形陶瓷刀具微波烧结技术研究

利用微波烧结技术实现了复杂刃形陶瓷刀具的高效制备。仿真研究了微波电场和温度场随试样加载方式的变化规律，实验验证了不同试样加载方式对陶瓷刀具致密度、力学性能和微观结构的影响以及复杂槽型陶瓷刀具的切削性能。研究结果表明，多个试样平行横放且处于微波烧结腔中心位置时，试样之间的电场强度均匀、温差小，更有利于多个试样同时达到致密。利用微波烧结技术制备的复杂槽型Al2O3/SiC陶瓷刀具刃形结构完整，具有较好的切削性能。相较于传统平刀面陶瓷刀具，复杂槽型陶瓷刀具的金属去除量提高了近2倍，加工表面粗糙度降低了约33%。基于微波烧结的复杂陶瓷刀具“结构-性能”一体化高效制造技术具有广阔的应用前景。     

Research on manufacturing Cu matrix Fe-Cu-Ni-C alloy composite parts by indirect selective laser sintering

The property of alloy parts can be adjusted conveniently if alloy element powders are used for manufacturing alloy parts by indirect selective laser sintering (SLS), but there have been no reports in this field. Fe, Cu, Ni, C composite powders of two compositions were obtained through a 3D blending way in this paper. Green parts of above composite powder were manufactured by indirect SLS. Then, Cu matrix Fe-Cu-Ni-C alloy composites were produced after green parts had been depolymerized, high temperature sintered and infiltrated by molten Cu. The post-processing of green parts, microstructure and mechanical properties of alloy composites were investigated. The results show: Ni, Cu and C diffuse into γ-Fe when green parts are being sintered at high temperature and the distributing non-uniformity of alloy elements is eliminated basically; at room temperature, alloy composite microstructures are composed of lower bainite, α-Cu precipitated out of γ-Fe and Fe-Ni after they have been solution treated at 930°C and held at 350°C for 1 h later; the yield strength of alloy composites is near to 400 MPa and the elongation is under 3%. It can be used for manufacturing injection mold or other functional parts by indirect SLS.     

Investigation into the selective laser sintering of styrene–acrylonitrile copolymer and postprocessing

The amorphous polymer of polystyrene (PS) has been widely used in the selective laser sintering (SLS) process. However, PS is not suitable to make parts with thin-wall or delicate structures because of the poor mechanical properties of its SLS parts. Therefore, styrene–acrylonitrile copolymer (SAN), another kind of amorphous polymers, was investigated as an SLS material. The effects of laser energy density on the relative density, mechanical properties, and dimensional accuracy of the SLS parts were studied, and the properties of PS and SAN SLS parts were compared. The postprocessing method of infiltrating with epoxy resin was used to reinforce the green SAN SLS parts. The results show that there is little difference in the relative density between the SAN and PS SLS parts, while the flexural strength of the SAN SLS specimens is obviously higher than that of the PS SLS specimens at the same energy density. After the postprocessing, the flexural strength, flexural modulus, and impact strength of the SAN SLS specimens increase by 133%, 4394%, and 254%, respectively, and the SLS parts maintain relatively high-dimensional accuracy although slight shrinkage occurs due to epoxy resin cure. SAN can be used to fabricate SLS parts with more complex and delicate structures.     

纳米银双面烧结SiC半桥模块封装技术

为满足雷达阵面高功率密度的需求,SiC宽禁带半导体器件在电源模块应用中逐步取代传统硅功率器件。传统焊接及导电胶粘工艺存在导电性能差、热阻大、高温蠕变等缺点,无法发挥SiC功率器件高结温和高功率的优势。纳米银烧结是大功率器件最合适的界面互连技术之一,具有低温烧结高温使用的优点和良好的高温工作特性。文中针对高功率电源模块大电流传输对低压降及高效散热的需求,基于高功率半桥电源模块开展了SiC芯片的纳米银双面烧结工艺技术研究,突破了成型银焊片制备、纳米银焊膏高平整度点涂、无压烧结等关键技术,并通过烧结界面微观分析以及芯片剪切强度和焊片剥离强度测试对烧结工艺参数进行了优化。最后对半桥模块进行了静态测试和双脉冲测试。该模块的栅极泄漏电流<1.5 n A,开关切换时间<125 ns,漏极电压过冲<12.5%,满足产品应用需求。     

纳米陶瓷粉末激光选择性烧结初探

在分析纳米陶瓷材料烧结成形技术基础上，结合选择性激光快速成形的最新发展，针对纳米陶瓷材料在烧结应用中遇到的难题，提出了一种全新的纳米粉末材料烧结的方法，即纳米陶瓷粉末激光选择性烧结。结果表明，在所选的工艺参数下，Al2O3及SiC纳米陶瓷粉末烧结后仍保持在原有的纳米尺度，基本没有长大，且所获得的烧结块体致密。同时对影响烧结的关键因素进行了讨论。     

覆膜钼粉激光烧结成型件的高温烧结工艺研究

高温烧结是选择性激光烧结后处理工艺的关键问题之一，传统上高体积质量的合金烧结采用单一液相烧结法，但这种烧结方法不适用于保形性差的激光烧结件。通过对覆膜钼粉脱脂预烧结件进行真空固相烧结与还原气氛二步烧结，研究2种高温烧结件的组织及性能后发现，还原气氛对改善烧结体组织具有显著作用，二步烧结可以实现保持制件形状的液相烧结。