Diffusion aluminide coatings for protecting the surface of the internal space of single-crystal turbine blades made of rhenium- and rhenium-ruthenium-containing high-temperature alloys: Part II

The production of heat-resistant aluminide and chromium aluminide protective coatings with a barrier layer, which is based on the carbides of the refractory elements of a nickel superalloy, is considered for the powder methods of diffusion chromium and aluminum saturation of the surface of the internal space of single-crystal high-pressure turbine blades made of high-temperature rhenium- and rhenium-ruthenium-containing alloys for a gas turbine engine. The barrier layer is shown to prevent the formation of a secondary reaction zone, which softens an alloy, under a heat-resistant coating during long-term high-temperature holding. The kinetics of powder-assisted aluminizing and chromizing-aluminizing of high-temperature rhenium- and rhenium-ruthenium-containing alloys is studied, aluminizing and chromizing-aluminizing conditions are determined, and the effect of heat-resistant diffusion coatings with a barrier layer on the mechanical properties of the high-temperature alloys is investigated.     

Heat-resistant coatings for the high-pressure turbine blades of promising GTEs

Heat-resistant coatings are considered for the external surface of high-pressure turbine (HPT) single-crystal blades for promising gas turbine engines (GTEs) made from carbon-free nickel superalloys with rhenium or rhenium plus ruthenium. Nickel superalloys covered with heat-resistant coatings consisting of heat-resistant connecting layers and an external ZrO₂-(7–8 wt %)Y₂O₃ ceramic layer are subjected to heat resistance and high-temperature tests. The test results are used to choose the heat-resistant layer that ensures the highest properties of a composition heat-resistant coating. The use of sequential chemical and physical deposition methods for coating layers is shown to be required to protect HPT blades in promising GTEs. Medium-frequency magnetron plasmachemical deposition of ceramic layers in heat-resistant coatings with a low thermal conductivity is found to be promising.     

钛合金表面微弧氧化耐磨和耐蚀膜层的研究进展

微弧氧化是一种直接在有色金属或其合金表面原位生成陶瓷膜的新技术,利用该技术可在钛合金表面生成耐磨和耐蚀性能优良的膜层。介绍了微弧氧化技术及其特点、钛合金表面微弧氧化耐磨和耐蚀膜层的研究进展,并指出了钛合金表面微弧氧化耐磨和耐蚀膜层的应用前景和今后膜层研究的发展方向。     

Protective Coatings on Heat-Resistant Nickel Alloys (Review)

The literature on materials for protective coatings on heat-resistant nickel alloys and methods for their production is reviewed in order to generalize the results and determine the principal directions for solution of the problem under consideration. It is shown that a promising approach is the development of layered composite ceramic coatings which, thanks to a graded variation of properties, are able to provide an optimal combination of adherence, mechanical strength, and corrosion and heat resistance. The methods of physical vapor deposition, plasma spraying, and electron-beam deposition remain the principal industrial processes for coating deposition.     

耐热铝合金的研究及应用现状与展望

文章综述了航空航天、高压输电、核乏燃料贮存、石油钻探等主要领域用耐热铝合金的性能特点、开发及应用现状,对耐热铝合金应用前景进行了展望,并提出了我国耐热铝合金研发和产业化发展建议.     

Influence of iron and silicon on the phase composition and structure of heat-resistant casting nikalines strengthened by nanoparticles

The phase composition of the Al-Ni-Mn-Fe-Si-Zr system is analyzed as applied to heat-resistant nikalines (aluminum alloys of a new generation based on Ni-containing eutectic), which are strengthened by the Al₃Zr (L1₂) nanoparticles. It is shown that the presence of iron and silicon considerably complicates the phase analysis when compared with the AN4Mts2 base alloy. Silicon strongly widens the crystallization range, which increases the tendency of the alloy to form hot cracks during casting. It is shown that economically doped nikaline AN2ZhMts substantially exceeds the most heat-resistant cast aluminum alloys of the AM5 grade in the totality of its main characteristics (heat resistance and mechanical and production properties).     

医用钛合金及其表面改性技术的研究现状

介绍了新型医用钛合金的研究开发现状，分析了医用钛合金存在的主要问题，即耐磨性、耐腐蚀性和生物活性有待进一步提高。阐述了表面改性对提高钛合金的耐磨性能、耐腐蚀性能和生物活性的作用。指出应当重视钛合金表面生物活性陶瓷涂层的稳定性问题。认为通过研究开发综合性能更优的新型医用钛合金，寻求更为理想的表面改性工艺以及运用复合涂层制备技术，有望逐步解决钛合金在临床应用中存在的问题。     

The use of self-propagating high-temperature synthesis and argon-arc overlaying when strengthening the surface of products made of titanium alloys

A new method for the deposition of protective coatings (wear-resistant overlaying) that are 2 to 10 mm thick and more on the surface of titanium articles is suggested, developed, approved, and patented. The method, called “SHS-arc overlaying,” combines the exothermic synthesis of adding material (AM) and argon-arc overlaying, which proceed simultaneously with the deposition of the coating. AMs made of exothermic mixtures are developed. Using this new method, protective composite coatings for titanium articles are obtained. The physicochemical, microstructural, and exploitation properties of the overlaying are investigated. Its operational characteristics exceed the characteristics of standard samples by a factor of 1.5–2.0. This new technology can be recommended for the deposition of protective coatings on products of wide indentation made of titanium alloys.     

Extrusion, Properties, and Failure of Spray-Formed Hypereutectic Al-Si Alloys Based on the Optimization of Fe-Bearing Phase

Based on the densification of the spray-formed hypereutectic Al-Si (hyper-AS) alloys, the microstructural evolution, mechanical properties, as well as the failure are studied in this investigation. The appropriate process and parameters for the densification of the deposits are gained from the thermomechanical simulation. Besides of the spray-formed Al-25Si-5Fe-3Cu (3C) alloy, the microstructures of other spray-formed alloys with Mn/Cr addition are stable without coarsening of the refined α-Al(Fe,TM)Si (TM = Mn/Cr/(Mn+Cr)) particles, which can improve the heat resistance. Especially, a great number of the submicrosized α-Al(Fe,TM)Si phases are observed in the hot-extruded TM-containing alloys. The critical ranges of the major parameter TM/Fe mass ratios that can affect the formation of the α-Al(Fe,TM)Si phases in the cast or spray-formed hyper-AS alloys are severally determined. The structure and lattice constant of the refined α-Al(Fe,TM)Si phases also are characterized. The mechanical properties of the current extruded hyper-AS alloys at room or elevated temperatures are close to or higher than some commercial alloys or other published results. Therefore, the hyper-AS alloys can be proposed as new lightweight, heat-resistant, and high-strength alloys, which can be used in the complex working conditions, such as advanced engine systems. The main reason for the enhanced properties would be the formation of a large quantity of microsized/submicrosized α-Al(Fe,TM)Si phases and abundant dislocations, which can greatly reinforce the matrix and transform the brittle fracture of the needle-like Fe-bearing phases into ductile fracture.     

Fundamental considerations for the development of oxidation-resistant alloys and coatings based on γ-TiAl

Alloys based on γ-TiAl are promising high-temperature materials that may replace conventional heat-resistant steels and superalloys in applications where high strength in combination with low density is required. However, an important hindrance to the use of γ-TiAl alloys at high temperatures is their relatively poor oxidation resistance and sensitivity against environmentally induced embrittlement. This material degradation is related to the poor protective properties of the mixed TiO₂/Al₂O₃ surface scales which form on the surface during high-temperature exposure. Recently, it was shown that protective alumina scale formation on γ-TiAl can be obtained by small additions of Ag. This effect was found to be related to the formation of Z phase in the subscale depletion layer at the expense of α ₂-Ti₃Al. It was found that the beneficial effect of Ag can be suppressed if the alloys contain additional α ₂-stabilizing elements, such as Nb, as is the case for most (semi)commercial, high-strength alloys. Therefore, recent efforts have concentrated on developing Ag-containing γ-TiAl alloys as oxidation-resistant coatings for high-strength titanium aluminides. Preliminary results using magnetron sputtering have shown that, due to the similarities in chemical and physical properties of the coating and base material, the Ag-containing material offers promising potential to be qualified as a coating material for reducing the oxidation-induced degradation of titanium aluminides. This article is based on a presentation made in the symposium entitled “Fundamentals of Structural Intermetallics,” presented at the 2002 TMS Annual Meeting, February 21–27, 2002, in Seattle, Washington, under the auspices of the ASM and TMS Joint Committee on Mechanical Behavior of Materials.     

铝基TiC–TiB2自蔓延高温合成复合涂层的组织性能研究

以Ti粉、石墨粉、B₄C粉、聚四氟乙烯粉(polytetrafluoroethylene, PTFE)为原料, 采用反应熔覆技术, 结合自蔓延高温合成与真空消失模鋳造法, 在ZL205A铝合金表面制备出TiC-TiB₂复合涂层, 研究了固溶温度对基体和TiC-TiB₂涂层显微组织、硬度和热稳定性的影响, 为制备高耐磨性铝合金提供新的研究方向。结果表明: Ti-C-B₄C-PTFE体系的绝热温度的远大于1800 K, 自蔓延高温合成反应可自发进行; 通过真空消失模铸造ZL205A铝合金, 引发自蔓延高温合成反应, 在基体表面可形成TiC-TiB 2复合涂层。固溶热处理后TiC-TiB₂复合涂层表现出良好的热稳定性, 硬度为HB 285, 20 N载荷作用下的质量损失量为49.7 mg, 相对减少了90%, 大大提高了ZL205A铝合金表面的耐磨性。     

热喷涂制备非晶合金涂层性能的研究进展

首先介绍了非晶合金的理论基础,然后从耐磨性和耐蚀性两个方面入手,详细地阐述了国内外对于热喷涂非晶合金涂层性能研究进展情况,并系统地总结了非金合金涂层在耐磨性和耐蚀性上的本质联系和根本矛盾,最后指出热喷涂非晶合金涂层性能研究上的局限性,提出三点问题:对于非晶合金基础理论的研究还处在起步阶段、热喷涂制备非晶合金涂层的合金体系种类少、制备非晶合金涂层的热喷涂技术有待开发,并针对以上三点问题提出热喷涂制备非晶合金涂层性能研究的未来发展方向。      

Nonsensitizing Zr–O–N Coatings for Jewelry Made of Nonprecious Alloys

In recent decades, jewelry manufacturers have started using nonprecious alloys to decrease production costs. A large number of customers, however, have an allergic (sensitizing) body reaction to jewelries made of such materials. The application of nonsensitizing coatings can decrease the negative influence of the jewelry material on the human organism. One material biologically inert towards human body tissues is zirconium. In this study, zirconium-based coatings applied by magnetron sputtering are examined. Eleven regimes of applying zirconium oxynitride coatings onto a substrate of AISI 430 grade steel are investigated. Microhardness and corrosion tests of the coatings in Hank’s solution are conducted and color performance is determined in the CIE 1976 L*a*b* and RGB color spaces. The coating width is 0.4–1.2 μm. It is established that the coatings have a microhardness of 2.5–3.0 GPa and are able to imitate colors of jewelries. Using energy dispersive X-ray spectroscopy, it is established that the coatings consist of Zr, N, and O. The authors select sputtering conditions that produced metallic coatings with high optical reflectance in an energy range near the infrared region of the spectrum (<1.7 eV) of golden color with high lightness. It has been experimentally proven that the coatings do not corrode in Hank’s solution. The allergy patch test of jewelry with the zirconium oxynitride coating conducted on a respondent with sensitizing reaction to nonprecious alloy jewelry has demonstrated a good result—no signs of skin allergy were observed. The results allow us to recommend magnetron sputtering as a technique for applying zirconium-based coatings onto jewelry of nonprecious alloys.     

铈镧混合稀土对AZ91D压铸镁合金显微组织和蠕变性能的影响

研究了不同含量Ce/La(x=0,0.1,0.5,1.0)对AZ91D镁合金显微组织及蠕变性能的影响。通过X射线衍射(XRD)、金相显微镜(OM)、扫描电镜(SEM)及能谱分析(EDX)观察与分析表明,压铸AZ91D镁合金中添加Ce/La后,除了α-Mg,β-Mg17Al12相之外,还生成了新的稀土化合物Al11RE3(RE=Ce/La)化合物,并且细化了合金显微组织、提高了合金室温和高温力学性能。生成的Al11RE3(RE=Ce/La)高温热稳定相使AZ91D+xCe/La(x=0,0.1,0.5,1.0)合金在150℃,50MPa下的蠕变抗力优于AZ91D镁合金,1%Ce/La的合金与AZ91D相比,蠕变延伸率低了0.2%,最小蠕变速率从2.30×10-8s-1降低到2.02×10-8s-1。蠕变试样的微观组织结构分析表明:AZ91D合金的蠕变机制主要以晶界滑移方式为主,Al11RE3(RE=Ce/La)热稳定相在晶界处延缓和阻碍了晶界断裂的过程。     

Oxidation Resistance of Niobium Coated with Titanium Disilicide

Coatings based on TiSi₂ have been used to protect niobium alloys from corrosion at temperatures up to 1300°C. Kinetic oxidation curves are given for these coatings on niobium. The phase compositions of the coatings have been determined and also of the layers formed during oxidation. EPMA has been applied to the element distributions in the coating, from which it is concluded that the silicon is mobile. The high resistance to oxygen of coatings based on TiSi₂ is due to the formation of films of TiO₂ and SiO₂ on them.     

Effect of extended solid solution of Hf on the microstructure of the laser clad Ni-Fe-Cr-Al-Hf alloys

Alloys and coatings for alloys for improved high temperature service life under aggressive atmosphere are of great contemporary interest. There is a general consensus that addition of reactive elements such as Hf will provide many beneficial effects for such alloys. The laser cladding technique was used to produce Ni-Fe-Cr-Al-Hf alloys with extended solid solution of Hf. A 10 kW CO₂ laser with mixed powder feed was used for laser cladding. Optical, scanning electron (SEM) and scanning transmission electron (STEM) microscopy were employed for microstructural evolution of alloys produced during laser cladding processes. The electron probe microanalysis and the auger electron spectroscopy were also used for micro-chemical analysis of different phases. Microstructural studies revealed a high degree of grain refinement, considerable increase in solubility of Hf in matrix and Hf rich precipitates and new metastable phases. This paper will report the microstructural development in this laser clad Ni-Fe-Cr-Al-Hf alloy.     

Progress in Research on Vanadate-Based Coatings on Corrosion Resistance

Vanadate, usually used as the corrosion resistant inhibitor for the paint systems, is one of the substances that have been proposed as alternative to toxic chromate for the corrosion protection. In this paper, the possibility of vanadate passivating from its chemical properties was introduced firstly. Then, the progress and examples in research on vanadate conversion coatings on the corrosion resistance were summarized. And the substrates discussed here contained aluminum alloys, magnesium alloys and so on. Finally, the research tendency of vanadate-based coatings was discussed.     

Oxidation Resistance of Niobium Coated with Titanium Disilicide

Coatings based on TiSi₂ have been used to protect niobium alloys from corrosion at temperatures up to 1300°C. Kinetic oxidation curves are given for these coatings on niobium. The phase compositions of the coatings have been determined and also of the layers formed during oxidation. EPMA has been applied to the element distributions in the coating, from which it is concluded that the silicon is mobile. The high resistance to oxygen of coatings based on TiSi₂ is due to the formation of films of TiO₂ and SiO₂ on them.

     

Mg-Al-Zn-Ca系耐热镁合金的发展与应用

阐述了耐热镁合金的研究现状;介绍了碱土元素Ca对Mg-Al-Zn系合金的微观组织、抗蠕变性能的影响及其应用,同时对Ca在镁合金中的应用前景作了展望.     

Structure and Corrosion Resistance of Microarc Oxidation Coatings on AZ91D Magnesium Alloy

Magnesium alloys are widely used as shells of 3C (computer, mobile phone and consumer electronics) equipments for its impressive mechanical and physical properties, such as low density, good resistance to electromagnetic radiation, suitable for high pressure diecasting and easily recycling, etc. But poor corrosion resistance confines its extensively application. In this paper, protective coatings was successfully prepared on AZ91D magnesium alloys by micro-arc oxidation (MAO) and painting process. Microstructures and phases of MAO coatings were invesgated with scanning electron microscope (SEM) and X-Ray diffractometer. Mechanical properties of MAO coating, such as adhesive force and corrosion resistance, were also tested. Results showed that MAO coatings were a good base for painting process. MAO coatings with paint have good adhesive properties to base metal and excellent corrosion resistance. Micro-arc oxidation with painting process is a good kind of surface treatment to improve the corrosion resistance of mobile phone shell made of AZ91D magnesium alloys.