金属零件的激光直接快速制造

简要介绍了一种快速制造金属零件的新方法－激光直接制造法及其特点，它是将激光表面涂覆技术和快速原型技术相结合来直接制造金属构件。回顾了国内外研究的现状，指出了目前存在的问题和将来的发展前景。     

注射成形金属粉末零件

本文详细叙述了目前金属粉末注射成形的具体工艺过程,在过程中使用各种不同方法的优缺点;金属粉末注射成形零件的设计参数和它与普通成形方法相比较的竞争性。     

注射成形钛零件的研究

金属粉末注射成形(MIM)是一种极具竞争潜力的钛零件低成本近终形规模制造技术,控制氧、碳污染和收缩畸变是工艺过程的关键。通过不同种类钛粉的组合,可调整体系的粉末形状和粒度组成,降低初始氧含量,改善注射、脱粘和烧结过程的工艺特性;优先选择可通过溶解、蒸发和低温裂解去除的有机粘结剂;溶剂萃取,高真空和高纯、低露点Ar气有利于高效低污染脱粘,脱粘终点为0.16%~0.20%C;增加相对密度有利于提高强度,降低氧、碳污染程度可显著加大伸长率,而烧结过程中的温度和真空度是主要因素;MIM-Ti的基本力学性能与I/M-Ti 3~4级相当,尺寸精度可控制在±(0.18~0.20)%。     

金属注射成形——21世纪的金属零件成形工艺

金属注射成形(Metal lnjection Molding,简称MIM),进入21世纪以来,得到了快速发展,应用范围越来越广,引起了人们广泛关注,称之谓21世纪的金属零件成形工艺。本文简要介绍了MIM工艺的生产过程,优势,材料及工艺设计准则。     

金属原型零件渗铜烧结及其放电加工行为

研究了激光烧结快速成形技术制备金属原型零件的渗铜烧结处理工艺。通过放电加工试验以及对原型零件表面组织结构的分析，讨论了原型零件的放电加工行为，结果表明，经渗铜烧结处理的原型零件可获得与常规电极相近的加工性质，并且表现出优于常规电极的特性。     

难熔金属注射成形的研究

采用金属粉末注射成形技术成功制得了形状复杂的纯钨和纯钼零件。粉末注射成形工艺为：粉末装载量为52%,注射温度为165℃,注射压力为65 MPa,溶剂脱脂＋热脱脂两步脱脂法,经2300℃氢气气氛烧结,钨烧结样品的密度可达18.26 g.cm^-3,相对密度为94.61%;经1900℃氢气气氛烧结,钼烧结样品的密度为9.7 g.cm^-3,相对密度达95.09%,制品尺寸精度控制在±0.3%以内。同时,通过实验对比研究了掺加少量的稀土氧化物（La2O3,Y2O3）对注射成形钨和钼制品性能的影响。实验结果表明：稀土元素氧化物的添加,提高了注射成形钨和钼制品烧结后的密度,明显细化了烧结后样品的晶粒,稀土氧化物作为第二相粒子弥散分布于晶界处,提高了注射成形钨和钼制品的强度。     

直接切片技术在直接金属激光烧结系统中的应用

通过visual basic对硬件的开发,把直接切片技术应用到直接金属激光烧结快速成形系统中,并通过试验验证了此方法的可行性,取得了良好的试验效果.     

激光直接沉积成形Ni3Al合金的裂纹分析

激光直接沉积成形技术给Ni3Al合金提供了更广泛的应用场景,但成形过程中的热裂倾向限制了其应用.对Ni3Al合金激光直接沉积成形热裂问题展开研究和讨论,通过微观表征及力学性能测试探究了裂纹形成机制,并提出了相应的成形工艺优化方案.结果表明:Ni3Al合金在激光直接沉积成形时,会产生明显的宏、微观沿晶裂纹.枝晶偏析使得晶...     

Al/SiC复合材料激光快速成形的研究

激光快速成形技术制备Al/SiC复合材料基于快速成形原理，通过激光熔化同轴输送的Al/SiC复合粉末，在基板上直接成形出薄壁样品。鉴于Al/SiC复合粉末的特点，采用基板预热并预涂覆吸光涂层以降低所需的激光功率，避免铝的过度熔化和SiC的分解。所制得的Al/SiC复合材料组织均匀、细小，SiC分解量很少且分布均匀，有少量的Al4C3,Al4SiC4及单质硅生成。     

激光快速成型TC4钛合金的力学性能

金属零件的激光快速成型是结合CAD／CAM、高功率激光熔覆和快速原型制造的先进技术。研究了用激光快速成型技术制造TC4钛合金的力学性能，分析了低温退火和热等静压处理对力学性能的影响，并且测量了成型后试件的含氧量，观察了拉伸试件的断口形貌。研究结果表明激光快速成型制造的TC4钛合金的力学性能高于铸造组织的力学性能，达到了锻造组织的力学性能。     

Thermal Fatigue Behavior of AISI H13 Hot Work Tool Steel Produced by Direct Laser Metal Deposition

Direct laser metal deposition (DLMD) is an additive manufacturing technique getting growing attention thanks to the possibility of producing very complex parts in a short time and in a cost-effective manner. The possible applications of this technology are tools with conformal cooling channels and claddings for dies and molds reparation. One of the damaging mechanisms of tools is thermal fatigue (TF) cracking, leading to surface deterioration and, consequently, the processed parts. Herein, the TF behavior of DLMD-H13 submitted to two different heat treatments, namely direct tempering (T) and quenching and tempering (QT), is investigated. T does not significantly change the solidification microstructure after DLMD, whereas QT produces a more homogenous tempered martensite microstructure. A customary laboratory test is developed to induce TF damage under a cyclic temperature variation between 630 and 60 °C. The results evidence that the T-H13 has a slightly better TF resistance with respect to QT-H13 due to the higher tempering resistance of T-H13 with respect to QT-H13. Thus, according to TF test results, direct tempering can be preferred to quench and tempering since the elimination of quenching can decrease the costs of production as well as distortions-related issues, increasing the competitiveness of DLMD.     

激光熔覆技术研究进展

综述了近几年激光熔覆技术的研究进展,包括了激光熔覆涂层材料、激光熔覆层组织、以及主要工艺参数对熔覆层的影响等,对激光熔覆涂层存在的主要问题进行了归纳总结。在此基础上指出了激光熔覆技术的主要发展方向。     

金属基体上YSZ过渡层及YBCO薄膜结构与沉积条件的关系

研究了两种在金属基体（ＨａｓｔｅｌｏｙＣ）上沉积的、以钇稳定的ＺｒＯ２（ＹＳＺ）为过渡层的ＹＢａ２Ｃｕ３Ｏ７－ｙ薄膜结构，并讨论了结构与沉积条件的关系。当沉积速率低时，ＹＳＺ层致密、均匀，存在织构取向，且与基体连接良好；而高速率沉积的ＹＳＺ层疏松，与基体结合差。ＹＢＣＯ薄膜的结构和性能与沉积时的基体温度相关。     

Laser Direct Metal Deposition Technology and Microstructure and Composition Segregation of Inconel 718 Superalloy

  Multilayer of laser direct metal deposition (DMD) was prepared by depositing a gas atomized pre alloyed powder with a composition close to Inconel 718 alloy on Inconel 718 high temperature alloy substrate. The effects of the DMD parameters on the build up rate and the structure of the deposited layer were studied. The laser DMD sample was further processed by a solution treatment. The microstructure and property of the laser DMD zone before and after heat treatment were investigated as well. The results show that the laser parameters of actual laser power of 650 W, scanning speed of 58 mm/s, beam diameter of 1 mm, powder feed rate of 645 g/min, with a corresponding specific energy of 90-130 J/mm2, can be recommended as optimum parameters for high build up rate of Inconel 718 alloy. Under the condition of optimized parameters, a directional solidification microstructure was obtained and the average distance between the columnar crystals was 5-10 μm. The microcomposition segregation was found between the columnar crystal trunk and columnar crystal. The elements of Nb, Mo, Ti concentrated in the columnar crystal trunk. After the heat treatment, the segregation was greatly minimized, and the segregation ratios were close to 1. The hardness of the laser deposited layer did not show obvious difference along the height of the layer either for the as deposited layer or for the heat treated layer. However, the microhardness of the laser DMD zone after heat treatment was obviously higher than that after the as deposited treatment. During the heat treatment process, some Nb and Mo rich phases precipitated and strengthened DMD layer.     

激光熔覆改性铁基合金涂层的硬度和耐磨性能研究

为提高石油钻井行业中工件表面涂层的硬度和耐磨性,提升工件使用寿命,本文设计开发了含Cr、V元素的三种铁基激光粉末,通过激光熔覆加工工艺进行涂层制备,对铁基激光涂层的物相、硬度和摩擦磨损性能检测,成功开发了硬度高达60 HRC,摩擦系数为0.6094,15分钟50N载荷条件下磨损量仅为0.0007 g的高耐磨铁基激光熔覆涂层,满足石油钻井行业对于高硬度、高耐磨、长寿命的涂层需求。     

Al-Pb系轴瓦合金的雾化沉积制备技术研究

用雾化沉积工艺方法制备了Ａｌ－８Ｐｂ－４Ｓｉ－１．５Ｓｎ－１Ｃｕ合金板坯,并与铝箔一起进行轧制复合试验。金相及ＳＥＭ观察表明：在沉积态Ａｌ－Ｐｂ合金中,富铅相颗粒细小且分布均匀,