Principles of Alloying of High-Temperature Nickel Alloys Resistant to High-Temperature Corrosion

Problems of alloying of high-temperature nickel alloys resistant to high-temperature corrosion in combustion products of low-grade fuel are considered. The relationship between the structure and properties of alloys and the alloying set that provides high service characteristics is studied. The obtained dependences are used to create new alloys resistant to high-temperature corrosion. Their structure and properties are described.     

Observations on the role of oxide scales in high-temperature erosion-corrosion of alloys

The results are presented of exposure to a controlled high-temperature erosive gas stream of a series of alloys, which were selected to represent the range of microstructures and mechanical properties available in commercial high-temperature alloys. Analysis of the kinetic and morphological data suggested that the high-temperature oxidation behavior of a given alloy plays a very important role in determining its erosion-corrosion behavior under the conditions studied. In terms of relative behavior, alloys which are weak but ductile at temperature, and which form tenacious oxide scales, exhibited the highest resistance to high-temperature erosion-corrosion. Simple models were developed to describe the expected interaction between high-temperature oxidation and erosion.     

Laser surfacing of ZhS26 high-temperature alloy with carbides

The numerous publications dealing with high-temperature surfacing focus mainly on the issue of resistance to high-temperature corrosion. Very few studies have been dedicated to the wear resistance of high-temeprature materials. Meanwhile, items fabricated from high-temperature alloys have to operate under a wide gamut of service conditions which require that they should have not only high heat resistance and high-temperature strength, but also improved wear resistance. The situation is aggravated still more because at elevated temperatures the contacting surfaces are more likely to seize. The failure of materials when they are raised to high temperatures adds to the danger of abrasive wear. In a search for ways and means of enhancing the wear resistance of parts fabricated from high-temperature alloys and operating under contact friction, a technique was investigated in this study for the laser surfacing of ZhS26 high-temperature alloy with refractory carbides. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 10, pp. 5–7, October, 1997.     

建筑用耐火H型钢性能与组织的研究

对工业试制耐火H型钢的力学性能和微观组织进行了研究。分析了回火温度及时间对微观组织的影响,探讨了耐火钢的高温强化机理。结果表明,建筑用耐火H型钢在室温时的显微组织为多边形铁素体、少量珠光体和少量马氏体的混合组织,细小、弥散分布的马氏体组织是建筑用耐火H型钢保持良好高温性能的一个主要原因。高温下良好的组织稳定性有利于提高耐火H型钢的高温性能。thermo-calc热力学软件计算结果表明．Mn、Mo、Cr等合金元素能大量固溶在渗碳体中,形成合金渗碳体,有利于阻止高温回火组织粗化,保持良好的高温性能。     

Single-Crystal Rhenium-Bearing Nickel Alloys for Turbine Blades of GTE

The compositions of high-temperature single-crystal nickel alloys with rhenium additives (more than 6% Re), which have strength characteristics corresponding to foreign single-crystal alloys of the third generation, are determined. The attained level of properties justifies the use of the scarce and expensive element. An alloy with 9% Re belongs to the fourth generation of single-crystal high-temperature alloys where high-temperature strength and rhenium content are concerned.     

材料在高温高压水溶液中的电化学行为研究现状与进展

综述了高温高压电化学池和电极的应用研究现状及存在的问题.介绍了高温水化学对材料腐蚀的影响.阐述了高温高压电化学技术应用在高温高压水溶液中的最新研究成果,包括高温E-pH图、极化曲线、电化学阻抗谱和电化学噪声,并提出了需要进一步研究的方向.     

Condensation and condensation-diffusion coatings for turbine blades made of high-temperature alloys with a directed crystal structure

Results of an investigation of condensation (condensed) and condensation-diffusion coatings for protecting working turbine blades made of high-temperature nickel alloys from high-temperature gas corrosion are presented. The coatings were deposited on specimens of a high-temperature model nickel alloy by the ion-plasma method.Translated from Metallovedenie i Tetmicheskaya Obrabotka Metallov, No. 4, pp. 15 – 18, April, 1996.     

Ion-Plasma Diffusion Aluminide Coatings for Gas Turbine Blades (Structure and Properties)

An ion-plasma method for depositing alloy diffusion aluminide coatings on high-temperature alloys, which favorably differs from the traditional processes, is considered. The special features of formation of ion-plasma diffusion coatings on the surface of high-temperature alloys in single-stage and double-stage processes are considered. The process of formation of such coatings and their effect on the long-term high-temperature strength of nickel-base alloys is studied. Examples of advantages of the new method are presented.     

Effect of Initial Microstructure on the Mechanical Behavior and Evolution of Structure due to High-Temperature Stretching of VT9 Titanium Alloy

The effect of the initial structure of double-phase titanium alloy VT9 on the mechanical behavior and changes in the structure due to high-temperature uniaxial stretching is studied. Values of structural parameters after deformation are presented for six initial structural states of the alloy. The characteristics of uniform and lumped strain are computed. The effect of high-temperature annealing preceding the deformation on the ductility characteristics is described.     

Combined coating for turbine blades of high-temperature gas turbine engines

A combined coating for protecting turbine blades of high-temperature gas turbine engines is studied. Comparative tests of coatings under laboratory conditions and of coated blades in engine operation are performed. The microstructure of the coating is studied and the concentration profiles of alloying elements are determined by the method of x-ray diffraction analysis. Tests for high-temperature strength are performed.     

Weldability and high temperature performance of welded joints of heat-resisting alloys

The applications of various heat resisting alloys applications depend upon the service temperature and the environment in which they are employed; austenitic stainless steels are employed mainly in the temperature region of approximately 850-950 K and Fe-base, Co-base and Ni-base superalloys are employed for high-temperature use at more than approximately 950 K. Problems concerning the integrity of weld procedures and high-temperature performance of weld zones should be considered for the application of these heat-resisting alloys to welded structures. In fact, most heat resisting alloys have poor weldability compared with carbon and low-alloy steels and are subject to problems such as cracking during welding. Furthermore, there are many instances of deteriorating high-temperature performance of the weld zone due to changes in the microstructure which accompany welding. On the other hand, heat-resisting alloys are employed in severe high-temperature environments and it is highly possible that there will be an occurrence of fissures and deterioration due to deformation, creep damage, oxidation and carburising. There are many cases where materials which have been in service for extended periods have increased weld crack susceptibility. Repair welding of these requires further attention to be given to the possibility of weld cracks.     

高温合金无缝管材的研制与生产

介绍了国内高温合金无缝管材的研制和生产情况。指出高温合金无缝管材的研制和生产的关键在于穿孔,综述了提高高温合金毛管合格率的主要工艺原则。     

高温吸收剂研究进展及改性碳化硅吸波特性

针对装备高温部位雷达隐身需求,论述了高温吸收剂的研究现状和最新进展.采用改性碳化硅高温吸收剂,制备了高温吸波材料,在室温和580℃高温下,材料在26.5～40 GHz频段内的反射率均小于-10dB,具有良好的吸波性能.     

High-temperature properties of particle-strengthened W-Re

In recent years there has been renewed interest in the development of tungsten alloys for space power and advanced aerospace propulsion systems. Tungsten alloys have great potential for ultrahigh-temperature applications because of their thermal capabilities and exceptional high-temperature mechanical properties. Recent investigations of second-phase particle-strengthened W-Re alloys show that fine HfC and ThO₂ particles significantly improve the high-temperature tensile and creep properties of tungsten alloys. The superior high-temperature strengths of these alloys above 2,000K are attributed to the strong interaction between these second-phase particles and dislocations as well as excellent stability of these particles.     

High-Temperature Interactions off Refractory Metals with Gases

The thermodynamics and kinetics of high-temperature gas/metal reactions are important for the processing and application of the group IVa, Va, VIa and VIIa refractory metals—Zr, Hf V, Nb, Ta, Mo, W and Re. This article surveys the reactions of these metals with O, N, C and H. Along with various types of gas/metal reactions, the equilibria and thermodynamics for the range of solid solution of the nonmetals are discussed. The kinetics and mechanisms of reactions with N₂, O₂, H₂O, CO and hydrocarbons are treated with an emphasis on the high-temperature regime since refractory metals are most frequently applied in high-temperature environments. Degassing reactions and steady states are also examined, as are some technical aspects of gas/metal reactions, including aspects of purification, doping and high-temperature treatments arid applications of refractory metals.     

Cube texture of recrystallization in three-layer ribbon substrates composed of nickel alloys Ni-4.8 at % W/Ni-11 at % Cr/Ni-4.8 at % W

The processes of the formation of recrystallization texture in the three-layer composite Ni-4.8 at % W/Ni-11 at % Cr/Ni-4.8 at % W ribbon, which was subjected to cold rolling with degrees of deformation of 98.4–99.3% and subsequent high-temperature annealing, are studied. The composite ribbon was found to be suitable for use as a substrate in manufacturing second-generation high-temperature ribbon superconductors. The estimation of magnetic properties showed that the specific magnetization of annealed composite ribbon at operating temperatures of high-temperature superconductors is lower than that of the Ni-5 at % W ribbon, which is currently widely used in practice.     

The strengthening effect of (Ni,Fe)Al precipitates on the mechanical properties at high temperatures of ferritic Fe–Al–Ni–Cr alloys

Strengthening through a homogeneous distribution of a second phase is a concept that is widely employed in high-temperature materials. The most prominent among this group are nickel-based superalloys which owe their high-temperature strength to finely dispersed Ni₃Al particles. Similar microstructures can be obtained in the Fe–Al–Ni–Cr system with B2-ordered (Ni,Fe)Al precipitates in a ferritic matrix. These precipitates lead to an increase of high-temperature strength compared to conventional iron-base high-temperature alloys. However, secondary precipitates form during air cooling from high temperatures and affect the ductility. The results show that the ductility can be improved by a two-step aging treatment. Within the stress and temperature range investigated, the dependence of the secondary creep rate on the applied stress of aged alloys can be described by a power law if a threshold stress is introduced.     

Effect of plastic deformation on the kinetics of phase transformations in the Cu-47Pd alloy

It has been established that the processes of high-temperature deformation of polycrystalline aluminum can be monotonic or jumplike. A monotonic time dependence of the root-mean-square voltage of acoustic emission observed in such a process corresponds to the monotonic character of deformation accumulation, whereas macroscopic deformation jumps are accompanied by single high-amplitude pulses of acoustic emission correlating with the strain rate in the jumplike portion. The technique has been developed, and activation parameters (activation energy and activation volume) of the high-temperature deformation process have been determined. The character of the dependence of the activation parameters on the mechanical stress and temperature indicates a good correlation of elementary deformation acts in the course of high-temperature deformation.     

High-temperature brazing alloys produced by mechanical alloying

Mechanical alloying (MA) is proposed and tested as an alternative method of producing high-temperature brazing alloys. The oxygen content and distribution in the volume of the particles were determined in the powders of the high-temperature brazing alloy, produced by MA and dispersion of the melt. To reduce the oxygen content, the mechanically alloyed powders of the brazing alloy were refined in nitrogen. The data are presented for the experimental brazed joints produced with high-temperature brazing alloys prepared by MA with or without subsequent refining.     

合金元素Si在钛合金中作用的研究进展

综述了Si在钛合金中作用的文献成果.主要内容包括Si在钛合金中存在状态及Si对钛合金室温、高温性能的影响.重点以蠕变和热稳定性能为主线,归纳总结了Si对钛合金高温性能的影响机理,并提出了含Si高温钛合金的设计原则,以期对以后高温钛合金的研究和设计提供帮助.