TiAl基合金高温抗氧化性能的研究进展

TiAl基合金具有密度低、熔点高、抗蠕变性能优良、比强度和比刚度高等优点,很有希望作为新型高温结构材料而得到广泛应用.然而由于其高温抗氧化性能较低,应用受到一定限制.从合金化技术、表面改性技术和粉末冶金技术3方面讨论了改善TiAl基合金高温抗氧化性能的有效措施.     

稀土掺杂TiAl基合金的研究进展

稀土元素掺杂改性TiAl基合金效果明显,其在组织和层片细化、高温力学性能改善、高温抗氧化性能提高方面作用显著,同时其与传统合金化元素还可产生一定的交互作用,进一步增强改善效果。在传统粉末冶金制备稀土掺杂TiAl基合金材料的研究基础上,从组织片层结构、高温力学和抗氧化性能等角度综述了稀土掺杂改性TiAl基合金材料现阶段的研究现状,并从一些关键技术问题角度分析了未来的研究方向。     

含硅合金熔体对TiAl基合金表面改性的研究

使用含硅合金熔体对TiAl基合金进行了表面渗硅处理，渗硅处理温度范围是：913－1053K，实施发现，TiAl基合金与Al-Si熔体之间发生了界面反应，界面生成以Si,Ti,Al三元素为主的灰白色基体和条状，小块状黑色相。表面处理后样品经1173K／100h高温氧化后，表层形成了Al2O3,SiO2等致密的氧化膜，并保留有稳定的Si-Ti-Al相，因而改善了表面氧化层结构，大大增强了TiAl基合金的高温抗氧化能力。     

添加高铌对TiAl合金组织和高温性能的影响

由于γ-TiAl合金低密度和高温时的高比强度,因此很有希望在航空和汽车工业的高温领域得到应用.但该合金低的延展性和抗氧化能力限制了它的实际应用.研究发现,添加第3组元可以提高TiAl合金的工程性能.因此,人们相继开展了在含铝45mol%～49mol%的TiAl基合金中添加Cr,Mn,Ta,Nb,W,No,Si,B等第3组元的微合金化研究工作.高铌TiAl合金具有优良的高温强度和室温延展性,抗氧化性能及热加工性得到明显改善.因此对于高铌含量的TiAl合金研究得到快速发展.但是关于含铝量小于45mol%和含Nb量大于10mol%的TiAl合金研究很少.     

TiAl合金热加工性能及其影响因素

TiAl合金以其轻质、耐高温等特点成为替代镍基高温合金的重要高温结构材料。具有优异热加工性能的beta−gamma TiAl合金是变形合金的主要研究方向。总结了TiAl合金的热加工性能研究现状,分析了高温无序α相对热加工性能的作用,对β相稳定元素进行了分类,并归纳了β相稳定元素对热加工性能及力学性能的影响规律,提出了变形TiAl合金的未来研究方向。     

发动机用TiAl表面双辉等离子制备W-Mo合金层及其高温氧化行为

目前采用双辉等离子表面合金化技术在TiAl合金表面制备W-Mo涂层的研究不多。通过SEM与XRD等测试手段,研究双辉等离子表面合金化技术在TiAl基体表面制得的W-Mo合金涂层在780℃温度下的氧化行为。研究结果表明:W-Mo改性合金在初期氧化阶段快速氧化增重,经过100 h氧化后,试样增重5.2 mg/cm2,有效改善了TiAl基体的高温抗氧化性能。W-Mo合金涂层对氧气扩散起到阻碍作用,使TiAl基体抗高温氧化性能获得显著提升。氧化处理后合金涂层表面未发生改变,形成了致密、均匀的氧化膜层。TiAl基体经100 h氧化后表面氧化膜主要是一种柱状晶结构,TiAl基体氧化产物包括金红石型TiO2以及刚玉2种成分。     

TiAl合金表面涂层技术研究现状

TiAl合金由于其密度低,比强度和比刚度高,是航空航天工业理想的新型高温结构材料.室温塑性差的问题已通过添加合金元素和显微组织调控等手段基本得到解决,进一步提高其高温抗氧化和耐磨性能已成为需要重点研究的问题.表面涂层技术为这一问题的解决提供了一条有效的途径,为此,综述了国内外TiAl合金表面涂层技术的研究现状,重点介绍了激光技术和热喷涂技术及其应用,并展望了TiAl合金表面涂层技术的发展趋势.     

我国钛铝合金领域专利技术发展综述

正随着航空、航天技术的发展,对航空、航天发动机所用高温结构材料的性能要求也越来越高,"更强、更刚、更耐热和更轻"成为对新型高温结构材料的要求。钛铝(TiAl)基金属间化合物合金具有密度低、高比强度、比刚度,以及抗高温蠕变性好及高温抗氧化能力强等特点,被视为在航空航天领域可代替镍基高温合金的新1代高温轻质结构材料。20世纪80年代美国宇航局、能源部及许多大公司已经开始对TiAl合金     

TiAl合金断裂韧性的影响因素及其韧化机制

TiAl基合金具有低密度、高比强度、高比刚度、良好的抗蠕变性能以及高温抗氧化性能等优点,成为一种很有希望的航空、航天及汽车用高温合金,但其断裂韧性低一直是阻碍TiAl基合金应用的重要原因。分析了TiAl基合金断裂韧性的主要影响因素,介绍了改善断裂韧性的主要途径,在此基础上概述了近年来关于TiAl合金韧化机制的论述,包括内在韧化和外在韧化机制。内在韧化来源于基体滑移和韧性相韧化,外在韧化机制起源于剪切韧带韧化、裂尖钝化、裂纹分叉、偏转和扩展、显微裂尖的屏蔽、孪晶韧化等。     

TiAl合金表面激光重熔等离子喷涂MCrAlY涂层研究

为了进一步提高TiAl合金表面等离子喷涂MCrAlY涂层的高温氧化性能,采用激光重熔工艺对涂层进行处理,研究了激光重熔对涂层微观组织及抗氧化性能的影响.用扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)分析了涂层氧化前后的表面形貌、微观组织和相组成.结果表明:经过激光重熔处理后,涂层片层状组织得以消失,致密性提高,消除了喷涂层的大部分孔洞、夹杂等缺陷,同时使Al元素在涂层表面的重新分布,形成了Al的富集区;等离子喷涂MCrAlY层能显著提高TiAl合金的抗高温氧化性能,经过激光重熔后可进一步提高其抗高温氧化性能.     

Nb-TiAl 金属间化合物研究现状

论述了Ｎｂ－ＴｉＡｌ系金属间化合物在高温强度及抗氧化性方面已取得的进展。高熔点组元Ｎｂ提高了合金的熔点和有序温度,从而使合金的使用温度达到９００℃以上。该体系合金显示出来的潜力具有代替Ｎｉ基合金的趋势。     

Neu entwickelte TiAl‐Basislegierungen für den Leichtbau von Triebwerks‐ und Motorkomponenten – Eigenschaften,Herstellung, Anwendung

Newly Developed TiAl Base Alloys for Lightweight Components in Jet Engines and Internal Combustion Engines – Properties, Production, Application Titanium aluminides are a most promising high temperature materials alternative to conventional heat‐resistant steels and superalloys for high‐performance automotive and aircraft engine applications. Intermetallic TiAl base alloys offer striking advantages for high temperature and mechanical loading applications. The specific weight of about 3.8 ‐ 4.1 g/ccm is low, the oxidation and burn resistance at temperatures up to 800 °C are good. The elastic stiffness is high and the temperature strength is enhanced. Feasible applications in combustion engines are valves, pistons and exhaust gas turbocharger rotors. Blades, vanes and discs for jet engines are under development, as well. Due to the extraordinary high specific Young’s modulus (ca. 46 GPa ccm/g) and 0.2 %‐yield strength up to 1 GPa of the TiAl base alloys in the as‐extruded state some applications at lower temperatures have also been taken into consideration, e.g. connecting rods and piston pins. The paper reviews constitutional related properties of the advanced TiAl base alloys with the respect to the industrial manufacturing of components and structural applications.     

渗碳处理提高TiAl基合金高温抗氧化性

研究了表面渗碳处理Ｔｉ－４８Ａｌ－２Ｃｒ－２Ｎｂ合金高温抗氧化性的影响，结果表明，渗碳处理显著地提高ＴｉＡｌ基合金高温抗氧化能力，归因于渗碳处理在试样表面层形成了具有良好的抗氧化性和高温热稳定性的多层结构的渗碳层。     

TiAl的抗环境性研究

ＴｉＡｌ吸氢量小,抗高温吸氢性优异。与镍基合金相比,ＴｉＡｌ抗燃气热腐蚀性及抗熔盐热腐蚀性均较好。ＴｉＡｌ的抗氧化性有限,未经表面改性处理时在８００℃以上尚不足以使用。合金化元素、显微组织、机械载荷、表面状态等均可影响ＴｉＡｌ的高温氧化行为。     

Recent Progress in the Development of Gamma Titanium Aluminide Alloys

Intermetallic titanium aluminides offer an attractive combination of low density and good oxidation and ignition resistance with unique mechanical properties. These involve high strength and elastic stiffness with excellent high temperature retention. Thus, they are one of the few classes of emerging materials that have the potential to be used in demanding high‐temperature structural applications whenever specific strength and stiffness are of major concern. However, in order to effectively replace the heavier nickel‐base superalloys currently in use, titanium aluminides must combine a wide range of mechanical property capabilities. Advanced alloy designs are tailored for strength, toughness, creep resistance, and environmental stability. These concerns are addressed in the present paper through global commentary on the physical metallurgy and associated processing technologies of γ‐TiAl‐base alloys. Particular emphasis is paid on recent developments of TiAl alloys with enhanced high‐temperature capability.     

化学热处理表面改性对TiAl基合金抗高温氧化性能的影响EI

研究了渗碳处理对Ｔｉ－４８Ａｌ－２Ｃｒ－２Ｎｂ（ａｔ．％）合金高温循环氧化性的影响。试验发现，表面渗碳处理能够显著地改善ＴｉＡｌ基合金抗高温氧化能力。使用ＳＥＭ、波谱分析、能谱分析和Ｘ射线衍射分析，研究了渗碳处理提高ＴｉＡｌ基合金抗高温氧化性能的机理。     

TiAl基合金的高温氧化及其保护

TiAl基金属间化合物由于其密度低、高温性能好,越来越受到人们的重视.简单介绍了TiAl基合金研究的重点以及研究现状,对TiAl系合金高温氧化机理进行了分析,重点讨论了高温防护涂层发展过程,并简要评述了涂层今后的研究方向     

Design,Processing, Microstructure,Properties, and Applications of Advanced Intermetallic TiAl Alloys

After almost three decades of intensive fundamental research and development activities, intermetallic titanium aluminides based on the ordered γ‐TiAl phase have found applications in automotive and aircraft engine industry. The advantages of this class of innovative high‐temperature materials are their low density and their good strength and creep properties up to 750 °C as well as their good oxidation and burn resistance. Advanced TiAl alloys are complex multi‐phase alloys which can be processed by ingot or powder metallurgy as well as precision casting methods. Each process leads to specific microstructures which can be altered and optimized by thermo‐mechanical processing and/or subsequent heat treatments. The background of these heat treatments is at least twofold, i.e., concurrent increase of ductility at room temperature and creep strength at elevated temperature. This review gives a general survey of engineering γ‐TiAl based alloys, but concentrates on β‐solidifying γ‐TiAl based alloys which show excellent hot‐workability and balanced mechanical properties when subjected to adapted heat treatments. The content of this paper comprises alloy design strategies, progress in processing, evolution of microstructure, mechanical properties as well as application‐oriented aspects, but also shows how sophisticated ex situ and in situ methods can be employed to establish phase diagrams and to investigate the evolution of the micro‐ and nanostructure during hot‐working and subsequent heat treatments.     

Effect of aluminising on high temperature oxidation resistance of TiAI cOmpounds

Abstract

Intermetallic compounds of TiAl were aluminised by pack cementation in the temperature range 700–900°C with a powder mixture of aluminium, NH₄Cl, and Al₂0₃ under a flow of argon gas. The coating products and oxidised products formed on the TiAl substrate were investigated by optical microscopy, X-ray diffraction, and scanning electron microscopy. Single layers of TiAl₃ were formed on the substrate of all the aluminised specimens. Through thickness cracks and pores were often observed inside the coating layers. High quality coating layers (7sim;30 μm) containing a very small amount of microcracks and pores were obtained by a treatment of 800°C for 3 h. The average surface hardness of the aluminised specimens (～1010 HV(25 mg)) was much higher than that of the TiAl (～396 HV (25 mg)), thus improving the wear resistance. In particular, the aluminising significantly improved the high temperature oxidation resistance. After the high temperature oxidation tests, four sublayers, i.e. α-Al₂0₃, TiAl₂, TiAl with a high aluminium content, and TiAl with a low aluminium content, from the surface, were formed on the substrate. These four sub layers contributed to a significant improvement in the high temperature oxidation resistance.