FeAl系合金抗高温氧化性能研究进展

FeAl金属间化合物具有优异的力学性能和抗高温氧化、硫化腐蚀性能,被公认为是高温结构材料、高温气体除尘领域内具有重要应用价值的新材料,因而成了人们研究的重点课题之一。系统地讨论了铁铝金属间化合物的氧化过程、机理以及研究的进展情况。     

铁铝金属间化合物及其涂层制备的研究进展

铁铝金属间化合物凭借其较高的高温抗蠕变能力、良好的耐磨性、抗高温氧化和硫化等优点得到了广泛关注,但其具有B2、DO3和A2三种晶体结构,晶型难以准确控制,且DO3结构在室温下脆性高,给制备和加工带来困难.这些缺点极大地限制了铁铝金属间化合物在工业中的应用.本文总结了包括传统熔铸法和粉末冶金法等常见的铁铝金属间化合物块体材料的制备方法,并重点介绍了近年来发展起来的增材制造法和冷喷涂、热喷涂等涂层制备方法.同时,针对涂层材料中铁铝两相的反应控制这一关键问题,本文聚焦如何预判铁铝涂层界面反应中原位生成的铁铝金属间化合物的化合反应发生顺序的研究现状,分析对比了两种预判方法——相图法和焓变值计算法.其中,相图只能表征热平衡状态下的相分布,各相区域代表该温度、成分条件下所能获得的最终产物,局限性大,较难准确预测实际热处理过程中铁铝金属间化合物的出现顺序和种类.通过从热力学角度进行焓变值计算,结合Kirchhoff公式,可计算并绘制常见铁铝金属间化合物的焓变值-温度曲线,进而分析铁铝金属间化合物的反应发生顺序.焓变值计算法的理论结果与已报道的实验结果具有较高的一致性,弥补了相图法的不足,对制备特定的铁铝金属间化合物具有十分重要的指导意义.     

促进铝化物科研成果向生产转化—美国GAMI的措施

铝化物是一种有着广阔应用前景的高技术新材料,主要包括镍、铁和钛的铝化物,例如Ni_3Al、FeAl和TiAl等,其主要用途是作高温结构材料。由于这类高温材料是具有有序结构相的金属间化合物,故又称高温有序合金或高温金属间化合物。与镍基高温合金相比,由于这类材料的高温性能更好,可在更高的温度下工作,比重轻,抗铝腐蚀能力     

FeAl金属间化合物研究现状

FeAl金属间化合物是一种新型的高温材料,在最近的研究中受到极大的重视,由于其具有长程有序的特殊结构,从而带来一系列优异的特性,如优异的高温抗氧化和抗硫化性、相对较低的密度和低廉的价格等.但室温脆性是FeAl金属间化合物的一个显著弱点.对FeAl金属间化合物近年来的研究现状包括FeAl金属间化合物的抗氧化、抗硫化性和室温脆性等进行了较为详尽的综述.     

Fe3Al基合金高温环境下的氧化和腐蚀抗力及应力前景

介绍了Ｆｅ３Ａｌ金属间化合物基合金的抗高温氧化性能、抗高温硫气氛腐蚀性能,在此 讨论了Ｆｅ３Ａｌ基合金在此环境下的应用。     

Fe_3Al基合金高温环境下的氧化和腐蚀抗力及应用前景

介绍了Ｆｅ３Ａｌ金属间化合物基合金的抗高温氧化性能、抗高温硫气氛腐蚀性能,在此基础上讨论了Ｆｅ３Ａｌ基合金在此环境下的应用。     

Fe3Al基金属间化合物涂层的研究进展

Fe3Al金属间化合物具有良好的高温性能,在钢表面制备Fe3Al基金属间化合物涂层能有效提高基体在高温下的抗氧化、耐腐蚀、耐摩擦和抗冲蚀性能,其抗硫化性能甚至优于不锈钢.相比于同等功能的陶瓷涂层,Fe3Al涂层与基体有更好的相容性.综述了Fe3Al基金属间化合物涂层的研究现状,介绍了涂层性能及影响因素,涂层制备的主要工艺方法和技术特点,主要包括热喷涂、堆焊、激光合成等.     

金属间化合物的高温腐蚀与防护

综述了有序金属间化合物，主要是Ｎｉ－Ａｌ，Ｔｉ－Ａｌ和Ｆｅ－Ａｌ系金属间化合物高温腐蚀与防护方面的研究结果，包括它们的氧化腐蚀机理、合金元素对其氧化腐蚀性能的影响以及它们所需的高温涂层等。     

Fe-Al金属间化合物氢脆效应研究现状

Fe-Al金属间化合物具有良好的抗氧化、抗硫化腐蚀性能以及高温结构性质,而且质轻价廉,在航空航天、汽车工业、能量转换系统、过滤材料等领域具有广阔的应用前景,但在室温下易发生环境脆化,这也是其未能得到大规模应用的主要原因。本文在介绍Fe-Al金属间化合物特性的基础上,重点综述了Fe-Al金属间化合物氢脆行为及其机制的实验和理论研究进展,提出了今后的研究方向。     

金属间化合物的高温腐蚀与防护

综述了有序金属间化合物，主要是Ｎｉ－Ａｌ，Ｔｉ－Ａｌ和Ｆｅ－Ａｌ系金属间化合物高温腐蚀与防护方面的研究结果，包括它们的氧化腐蚀机理、合金元素对其氧化腐蚀性能的影响以及它们所需的高温涂层等。     

Effect of chromium on the corrosion behavior of iron aluminides in thiosulfate-chloride solution

Aqueous corrosion characteristics of iron aluminides in thiosulfate-chloride solution were studied as a function of chromium addition. Four kinds of iron aluminides, namely, FA-61, FA-77, FA-72 and FA-78, were prepared by arc melting followed by thermomechanical treatment. The corrosion behavior in thiosulfate-chloride solution for the prepared alloys were investigated by electrochemical tests (potentiodynamic test, potentiostatic test and electrochemical impedance spectroscopy (EIS) measurement) and surface analyses. The results of the potentiodynamic test indicated that the breakdown potential increased with increasing Cr content. Cr additions were found to prevent passive film from undergoing pitting corrosion. In EIS measurement, the depression angle was inversely related to pitting resistance, and decreased with increasing chromium content. The SEM observations of the sample surfaces reveal the different forms of pit as a function of chromium content. The AES results give evidence that the thiosulfate ions are reduced on the metallic surface, which inhibits the repassivation process.     

Laser cladding of Zr-based coating on AZ91D magnesium alloy for improvement of wear and corrosion resistance

To improve the wear and corrosion resistance of AZ91D magnesium alloy, Zr-based coating made of Zr powder was fabricated on AZ91D magnesium alloy by laser cladding. The microstructure of the coating was characterized by XRD, SEM and TEM techniques. The wear resistance of the coating was evaluated under dry sliding wear test condition at room temperature. The corrosion resistance of the coating was tested in simulated body fluid. The results show that the coating mainly consists of Zr, zirconium oxides and Zr aluminides. The coating exhibits excellent wear resistance due to the high microhardness of the coating. The main wear mechanism of the coating and the AZ91D sample are different, the former is abrasive wear and the latter is adhesive wear. The coating compared to AZ91D magnesium alloy exhibits good corrosion resistance because of the good corrosion resistance of Zr, zirconium oxides and Zr aluminides in the coating.     

Some Characteristics of Automotive Exhaust Valve Alloys

The PH stainless steels and the nickel-base superalloys, can be evaluated for exhaust valve applications by considering their metallurgical, environmental and high temperature strength properties. The PH stainless steels are characterized by their good sulfidation and high temperature strength. Good PbO corrosion resistance is achieved with the low silicon, nickel containing alloys. Stable alloys show the greatest high temperature strength which can be improved further by a solution and age treatment. Aging below the optimum temperature of 760°C results in grain boundary sensitization and low impact properties while higher temperatures produce more of the discontinuous phase. The addition of refractory elements can be detrimental to the oxidation resistance of these alloys. The highest elevated temperature strength and best PbO and oxidation resistance is achieved with the nickel-base superalloys. These alloys are completely stable and highest strength at elevated temperatures is achieved with a solution and age treatment. These alloys show lower sulfidation corrosion resistance relative to the PH stainless steels, however this can be improved with higher chromium contents.     

Effects of alloying elements on the electrochemical characteristics of iron aluminides

Effects of alloying elements on the electrochemical characteristics of iron aluminides in the H2SO4, H2SO4+KSCN and HCl solutions were investigated using electrochemical tests. The corrosion morphologies in iron aluminides were analysed by utilising optical microscopy. It was found that the addition of Cr and Mo to iron aluminides increased the corrosion potential, pitting potential and repassivation potential. The active current density, passive current density and reactivation current density decreased as Cr and Mo were added. In the case of Mo addition, the passive current density was slightly higher in the H2SO4 solution than in solutions containing SCN- and Cl-. When B was added to samples, the corrosion potential and repassivation potential decreased, whereas the active current density, passive current density, reactivation current density and pitting potential increased. Iron aluminides containing Mo and Cr showed remarkably improved intergranular and pitting corrosion resistance to SCN- and Cl- solution. On the other hand, B addition accelerated granular and intergranular corrosion by precipitation of borides. This revised version was published online in November 2006 with corrections to the Cover Date.     

Role of surface passive films in the hydrogen embrittlement of iron aluminides

The room temperature hydrogen embrittlement problem in iron aluminides has restricted their use as high temperature structural materials. Previous studies have established that surface films affect hydrogen embrittlement (HE). The effect of surface passive layer on the hydrogen embrittlement behaviour of iron aluminides has been critically reviewed in this presentation. The role of thermomechanical treatments in affecting the mechanical properties has been discussed from a processing-structure-properties correlation view point. The alloy development philosophy to yield ductile iron aluminides has been outlined based on this review. Novel iron aluminide intermetallics that are being currently synthesized and characterized along these lines at IIT Kanpur are finally introduced.     

钛铝金属间化合物合金的扩散连接

钛铝金属间化合物合金具有比重轻、比强度高以厦良好的高温力学性能和抗氧化性，被认为是航空航天和军工领域最具有应用前景的高温结构材料。钛铝金属间化合物合金的工程实用化需要先进的连接技术，保证连接件既能够保留母材的性能而且接头具有高的变形和断裂抗力。固态扩散连接不存在熔化缺陷、焊接热裂倾向和组织热影响区等缺点。被认为是连接钛铝金属间化舍物合全有效的方法之一。本文简要地介绍近十多年来国内外对钛铝金属间化合物合金扩散连接研究的状况与进展。     

触变–塑变复合成形铸铁材料的耐磨损和抗腐蚀性能研究

目的 针对天然气压缩机用铸铁构件服役环境恶劣的情况,研究一种提升其耐磨损和抗腐蚀性能的成形工艺。方法 以天然气压缩机用FCD400铸铁材料为研究对象,通过熔融–冷却试验和热压缩试验获得FCD400铸铁材料在高温条件下的固–液相变规律、半固态触变成形性能、塑性成形性能。基于该铸铁材料性能建立合适的触变–塑变复合成形工艺方案。通过二段热压缩试验开展FCD400铸铁材料的触变–塑变复合成形的物理模拟,验证触变–塑变复合成形的可行性。随后,通过摩擦磨损试验和中性盐雾腐蚀试验,对比触变–塑变复合成形铸铁材料和原始铸态材料的耐磨损和抗腐蚀性能,验证触变–塑变复合成形的有效性。结果 触变成形阶段变形量为12 mm且塑性成形阶段变形量为20 mm的触变–塑变复合成形FCD400铸铁材料具有更加精细的珠光体片层,以及更高的硬度和更好的耐磨性能。触变成形阶段变形量为20 mm且塑性成形阶段变形量为12 mm的触变–塑变复合成形FCD400铸铁材料具有更加离散且细小的球状石墨,离散分布的细小球状石墨对基体的撕裂作用更小并能够减缓腐蚀速率。结论 通过调节触变–塑变复合成形工艺参数,能够实现对FCD400铸铁材料的耐磨损和抗腐蚀性能的主动调控。     

Creep of intermetallic composites

The creep behavior of nickel and titanium aluminides, molybdenum silicides, and their composites was evaluated as a function of stress and temperature to identify the effect of reinforcements on the creep resistance of these compounds. The deformation behavior was analyzed using a power-law creep equation. The experimentally determined activation energies and stress exponents were related to the rate-controlling mechanisms for each system. With reinforcements, there is no improvement in the creep strength in TiAl, some improvement in NiAl, particularly at low stresses, and notable improvement in MoSi and its alloys. Comparative analysis of the creep resistance of aluminides, silicides and the currently used superalloys was also provided. On the basis of the creep resistance, it was concluded that MoSi and its composites have high potential for application at temperatures greater than 1000 °C, and that they are potential competitors to somewhat more brittle ceramic-ceramic composites.     

Enhancement of high temperature strength and room temperature ductility of iron aluminides by alloying

Abstract

The chemical ordering in intermetallics results in reduced atomic mobility and therefore increased resistance to plastic deformation at elevated temperatures. This intrinsic source of high temperature strength leads to the inherent brittleness of polycrystalline ordered intermetallics at room temperature. The requirements for optimum high temperature strength and ductility at ambient temperature are often incompatible. Iron aluminides possess high strength up to 873 K. There is an anomalous (positive) temperature dependence of yield and flow strengths. Iron aluminides have yet to achieve satisfactory elevated load bearing capability. Alloy additions have the potential for improving elevated temperature strength and room temperature ductility; whichever is more critical for the application. Elements such as Cr, Ti, Mn, Co, and Mo produce higher flow stress due to solid solution strengthening. Elements such as Zr, Ta, Nb, Re, and Hf go into solution partly, reprecipitate, effectively pin dislocations and thereby cause strengthening. Mo, Zr, and Hf produce good tensile strength at elevated temperatures but ductility decreases. Element B strengthens by grain boundary cohesion. The improvement in room temperature ductility can be achieved through modification of the crystal structure by changes in stoichiometry, macroalloying, microalloying, and control of the environment. B, TiB₂, and Cr are notable for enhancing ductility. The paper is an overview of the present status of iron aluminides in this respect.     

高温时效后的310不锈钢高温硫腐蚀研究

研究了310不锈钢在气氛总压为10^-5Pa,于2.3％SO2－S2－8.8％N2气氛中600℃下的高温硫腐蚀行为。利用金相、能谱及X射线衍射等分析手段对其腐蚀形貌、成分及结构进行了分析。结果表明：310不锈钢于700℃,10000h时效在其晶界大量析出σ相,造成晶界附近贫Cr,从而降低了晶界抗硫腐蚀性能,使高温时效处理后的310不锈钢6抗硫腐蚀能力明显降低,未时效处理的310不锈钢以均匀腐蚀为主,时效处理后的则以晶界腐蚀为主,并伴随有均匀腐蚀。