国外钛和钛合金熔模精铸涂料浆的研究和发展

钛和钛合金的熔模精铸陶瓷型壳是以化学方式将粘结剂与耐火材料混合制成涂料浆,然后焙烧而成.在型壳制备中涂料浆是非常关键的部分.本文较全面地介绍了国外在铸造钛和钛合金涂料方面的研究现状,并对其发展趋势进行了简要的展望.     

钛合金熔模铸造石墨型壳

用熔模铸造法成形钛合金铸件,可提高金属利用率,减少机加工量,降低成本。因此,自七十年代中期,钛合金熔模铸件的产量逐年增加,应用范围逐步由静止结构件扩大到转动件。到目前为止,世界钛合金熔模铸件的年产量已达20多吨,其中绝大部分用于宇航和导弹工业。目前采用的铸型系统有三种: 1.难熔金属粉(钨、钼等)面层复合陶瓷型壳系统; 2.纯石墨型壳系统; 3.氧化物陶瓷型壳系统(包括热解炭复层的普通陶瓷型壳)。     

钛合金精密铸造用BaZrO_3基复合型壳的制备

研究了BaZrO3作为钛合金熔模铸造面层材料的可行性。以自主合成的BaZrO3作为型壳面层的主要耐火材料,钇溶胶作为粘结剂,制备出了BaZrO3基复合型壳。探讨了BaZrO3涂料的粘度和悬浮率随粉液比、级配变化而变化的规律。通过分析经不同温度、时间焙烧后型壳的抗弯强度和断口形貌,最终确定了复合型壳的焙烧工艺。研究表明,当粉液比为3.0、细粉含量为50%~60%(质量分数)时涂料具有最好的粘度和悬浮性。焙烧温度为1 500℃、保温4h时,复合型壳具有最好的抗弯强度。将BaZrO3基复合型壳用于TiNi合金熔模精密铸造时,发现型壳与TiNi合金熔体润湿性差,二者间反应层很薄,说明BaZrO3是较为理想的钛合金精铸的面层材料。     

熔模精铸型壳性能强化的研究现状

近净形熔模精铸是一种少切削的特种铸造方法,广泛应用于批量生产航空航天、汽车等领域的复杂结构件,对型壳性能提出了更高的要求。针对熔模精铸型壳性能,较全面地论述了耐火材料、粘结剂及添加物对型壳性能强化的研究现状。     

新型钛精铸用粘结剂及型壳制备工艺的研究

开发研究了一种用于钛合金熔模精铸型壳面层的新型ＬＪ８型粘结剂;叙述了用该粘结剂制备型壳的工艺过程。用这种型壳所浇注出的钛铸件表面粗糙度为Ｒａ２６μｍ,污染层厚度为３０μｍ以下,实际浇注试验表明,所研制的新型粘结剂完全适用于钛合金熔模精密铸造。     

定制型钛合金植入物的光固化3D打印及精密铸造

为了准确、及时地制造定制型钛合金植入物,提出利用光固化3D打印方法构建精密铸造熔模和整体型壳注模的制壳方法。结果显示,通过这种方法定制的钛合金植入物能够准确地反映患者的个体特征,所铸造的定制型植入物的化学成分、力学性能和精度均满足相应国家标准和医药行业标准,满足临床植入的要求,已完成临床案例100余例。     

钛合金熔模铸造型壳制备技术研究现状

熔模铸造技术已成为钛合金铸造技术中最为常用的铸造方法。本文针对钛合金熔模铸造型壳的制备,较全面地介绍了常用的耐火材料和粘结剂的研究现状,论述了涂料的配制、型壳的干燥、型壳的焙烧对型壳质量的影响。     

基于SLA技术的钛合金熔模精密铸造工艺

采用SLA光固化成型技术和钛合金熔模精密铸造相结合的方法,从SLA光固化熔模结构设计及制壳工艺、铸件浇注工艺、热等静压等3个方面展开工艺研究。结果表明,SLA光固化中空腔体熔模原型设计及型壳直接高温焙烧的工艺合理可行,有效解决了型壳开裂的技术难题;采用离心真空浇注和热等静压工艺,可保证复杂铸件的充填性和内部质量;该工艺成功研制出符合技术要求的铸件,其表面粗糙度可达6.3μm,尺寸精度达到CT6级,综合性能满足国军标要求。     

熔模铸造用型壳材料的优选

采用选择性激光烧结技术(Selective laser sintering,SLS),以PS(聚苯乙烯)粉为熔模材料,制备了环套环特征件的熔模。对两种成分不同的陶瓷型壳浆料的流变性、陶瓷型壳的显微组织和高温强度进行了测试分析,研究了针状石油焦结构对型壳性能的影响,最终选择性能更优的型壳制得特征件。特征件铸件精度达到CT4级,废品率降低为原来的30%,同时大幅缩短了新产品的试制研发周期。     

我国熔模精密铸造的历史回顾与发展展望

概述了熔模精密铸造的特点及在我国的整体发展现状。按照不同产品类别追溯了我国熔模铸造发展的历史、技术进展、行业现状。详细介绍了通用硅溶胶型壳工艺、钛合金熔模铸造工艺、铝合金熔模铸造工艺、石膏型熔模铸造工艺、水玻璃型壳工艺等多种工艺方法以及熔模精密铸造在航空、航天以及一般商用铸件上的应用。指出了我国熔模精密铸造与工业发达国家之间存在的差距,并对我国熔模精密铸造行业的发展提出了几点建议。     

国内外钛合金精密铸造型材料的发展概况

介绍了国内铸造钛合金用石墨型、难熔金属面层及氧化物陶瓷型面层型壳材料的发展与应用状况,比较了国内外在这一领域的技术差距,提出应开发、研究新型的无污染制壳材料。     

Evaluation of crucible and investment materials for lost wax investment casting of Ti and NiTi alloys

Abstract

The aim of this study is to assess the suitability of selected commercial ceramic crucibles for the investment casting of Ti6Al4V and NiTi alloys for jewellery purposes. A commercial vacuum tilt casting machine and a centrifugal casting machine were employed to cast the alloys in cold copper moulds or in refractory investment shells. The form filling of the shell and the crucible and investment reactions were assessed by microstructural investigation, chemical analysis and hardness profiles of the as cast items as a function of shell temperature. The reaction of the alloys strongly depended on the alloy, the crucible material, the coating of the crucibles and the temperature of the ceramic shell. Optimum results were achieved with yttria and yttria coated Al titanate crucibles for Ti6Al4V and NiTi alloys respectively. Improvement of the materials and process costs is necessary to allow the competitive casting of jewellery made from titanium alloys.     

Prediction and analysis of microstructural effects on fabrication of ZrB2/(Ti,W)C composites

Zirconium diboride matrix composites are strengthened by incorporating (Ti,W)C into the matrix ceramic. Cellular automata models were used to predict the microstructural effects on the ceramic materials. ZrB₂/(Ti,W)C composites were fabricated and then analyzed via X-ray diffraction. The effects of the (Ti,W)C compounds on microstructures of zirconium diboride matrix materials were also determined.     

Cutting performance of solid ceramic end milling tools in machining hardened AISI H13 steel

Ceramic tools have been widely used in the cutting of hard-to-machine materials, but the applications of solid ceramic milling cutters are limited due to their design and manufacturing restrictions. This research investigates the cutting performances of four solid ceramic end milling tools including Si₃N₄, Ti(C,N), SG4 and LT55 in machining hardened AISI H13 steel (HRC 60-62). The results show that the cutting forces of ceramic end milling tools are less than that of the referenced cemented carbide tool, and such ceramic tools of Si₃N₄, Ti(C,N) and LT55 produce better surface qualities and have longer tool lives. With excellent mechanical peoperties including hardness, bending srength and fracture toughness, the ceramic tool of Ti(C,N) presents the best cutting performance taking the cutting force, machined surface quality and tool life in consideration simultaneously. The research has proven the application feasibility of ceramic materials in the manufacture of solid tools. The solid ceramic end milling tools are geometric extensions for traditional ceramic tools and they can be used in machining hardened steels.     

ICP—AES在有色金属材料中的应用

近年ICP-AES的分析技术和装置不断发展和完善,该法已在许多领域中得到应用,本文叙述了ICP-AES在轻金属、重金属、难熔金属、贵金属、超导材料、精细陶瓷材料、稀土金属分析中的应用。     

Wear mechanisms of gradient ceramic nozzles in abrasive air-jet machining

The nozzle is the most critical part in abrasive air-jet machining equipment. Ceramics, being with high wear resistance, have great potential as abrasive air-jet nozzle materials. In this paper, a (W,Ti)C/SiC gradient ceramic composite was developed to be used as nozzle material. The erosion wear behavior of the (W,Ti)C/SiC gradient nozzle was investigated and compared with a conventional ceramic nozzle. Results showed that the gradient ceramic nozzles exhibited an apparent increase in erosion wear resistance over the conventional ceramic nozzles. The mechanism responsible was found to be that the tensile stresses at the entry region of the nozzle were greatly reduced when compared with the conventional nozzle. This effect may lead to an increase in resistance to fracture, and thus increase the erosion wear resistance of the gradient nozzle. It is indicated that gradient structures in ceramic nozzles are effective to improve the erosion wear resistance of conventional ceramic nozzles in abrasive air-jet machining.     

Ultra-High Strength TiC/Refractory High-Entropy-Alloy Composite Prepared by Powder Metallurgy

A TiC-based ceramic composite with refractory high-entropy-alloy (HEA) binders was developed through a novel reactive sintering method. In the process, refractory carbide powders were reacted with Ti powder at high temperature, and in situ formation of Ti carbides and refractory HEA phases occurred. The results indicate that only body-centered-cubic HEA phases and TiC phases are formed after the reactive sintering. The microstructure of the composite is homogeneous, consisting of ultra-fine TiC particles with an average size of 0.85 μm and HEA grains with an average grain size of 1.8 μm. The TiC/HEA composite shows an ultra-high room-temperature compressive strength (>3000 MPa), compared to 1790–2210 MPa for the conventional TiC cermets.     

Si3N4/AgCu/TiAl钎焊接头界面结构及性能

采用AgCu非活性钎料实现了Si3N4陶瓷与TiAl基合金的钎焊,确定接头的典型界面组织结构为:TiAl/Ti3Al+Ti(s,s)/AlCuTi/Ag(s,s)+AlCu2Ti/Ti5Si3+TiN/Si3N4陶瓷。钎焊过程中,活性元素Ti从TiAl母材溶解到钎料中与Si3N4陶瓷发生反应润湿,实现了TiAl与Si3N4陶瓷的连接。随着钎焊温度的升高及保温时间的延长,靠近Si3N4陶瓷的TiN反应层厚度增加,Ag基固溶体中弥散分布的AlCu2Ti化合物聚集长大成块状,导致接头性能下降。当钎焊温度T=860℃,保温时间为5min时接头抗剪强度达到最大值124.6MPa。基于反应热力学及动力学计算TiN层反应激活能Q约为528.7kJ/mol,860℃时该层的成长系数KP=2.7×10-7m/s1/2。     

DESIGN AND PROPERTIES OF A FUNCTIONALLY GRADIENT CERAMIC TOOL MATERIAL

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Machinability of hardened steel using alumina based ceramic cutting tools

Alumina based ceramic cutting tool is an attractive alternative for carbide tools in the machining of steel in its hardened condition. These ceramic cutting tools can machine with high cutting speed and produce good surface finish. The wear mechanism of these ceramic cutting tools should be properly understood for greater utilization. Two types of ceramic cutting tools namely Ti[C,N] mixed alumina ceramic cutting tool and zirconia toughened alumina ceramic cutting tool are used for our investigation. The machinability of hardened steel was evaluated by measurements of tool wear, cutting forces and surface finish of the work piece. These alumina based ceramic cutting tool materials produce good surface finish in the machining of hardened steel. In this paper an attempt is made to analyse the important wear mechanisms like abrasive wear, adhesive wear and diffusion wear of these ceramic cutting tool materials and the performance of these ceramic cutting tools related to the surface finish is also discussed here.