激光熔覆修复航空发动机风扇机匣TC4钛合金静子叶片

结合航空发动机大型风扇机匣TC4钛合金静子叶片的修复需求,研究了损伤叶片的激光熔覆修复工艺,对熔覆层成分、组织、显微硬度及力学性能进行了分析。试验结果表明,激光熔覆层TC4钛合金的O、N、H元素成分满足标准要求;激光熔覆区为具有魏氏体组织特征的柱状晶,柱状晶内部为细密的马氏体组织,热影响区为柱状晶和双态组织的混合组织,并逐渐过渡到基体的双态组织;激光熔覆层显微硬度平均比母材高15%,过渡平缓;激光熔覆TC4试样的室温拉伸、400 ℃高温拉伸、热暴露试验的强度结果均高于母材试样,断后延伸率稍低。采用单道多层熔覆工艺对受损叶片进行修复,验收合格后,风扇机匣得到使用。     

Interactions of hafnia/hafnon composites with molten silicate deposits

The article examines the chemical interactions between HfO₂/HfSiO₄ composites and melts that originate from siliceous debris ingested into gas turbine engines. Pellets with hafnon volume fractions of 50%, 70% and 100% were synthesized from powders of the pure components and exposed to two types of quinary siliceous deposits (one acidic and one basic) at 1400 °C for times ranging from 10 min to 4 h. Scanning and transmission electron microscopy examinations of reacted pellets show extensive melt penetration without evidence of an effective mitigating mechanism. Acidic melts preferentially react with hafnia to form hafnon while basic melts dissolve hafnon to form hafnia; in both cases, however, the melts penetrate extensively along grain and interphase boundaries. These processes are accompanied by swelling of the reaction layer followed by blistering and exfoliation of the affected coating material. The thermodynamics of the reactions, mechanisms of melt penetration, and implications for coating applications are discussed.     

润滑油闪点测定在发动机修理中的运用

介绍了利用石油产品闭口闪点测定仪测定润滑油中所含轻质油料含量的一种试验方法。根据润滑油闭口闪点温度的不同判断润滑油中是否混入轻质油料以及轻质油料在润滑油中所占的比例。试验证明:在油品使用过程中,从闪点的下降程度可以判断混入轻质油的含量。     

高性能纳米氧化锆热障涂层性能研究

采用HVOF 技术喷涂金属粘结层NiCrAlY 作为底层,采用APS 技术喷涂纳米氧化锆陶瓷层作为面层,制备高性能热障涂层。设计正交试验优化HVOF 和APS 工艺,分析了优化工艺制得的热障涂层的微观形貌及性能。分析表明,NiCrAlY 涂层孔隙率小于2%,纳米氧化锆涂层孔隙率为15%。通过胶膜法测得纳米氧化锆热障涂层喷涂态的结合强度为30.4 MPa,且涂层经1100 益水淬50 次后表面无宏观裂纹,热生长氧化层为致密的Al2O3。     

Multi-component strategy for remarkable suppression of thermal conductivity in strontium diyttrium oxide: The case of high-entropy Sr(Y0.2Sm0.2Gd0.2Dy0.2Yb0.2)2O4 ceramic

Anti-spinel oxide SrY₂O₄ has attracted extensive attention as a promising host lattice due to its outstanding high-temperature structural stability and large thermal expansion coefficient (TEC). However, the overhigh thermal conductivity limits its application in the field of thermal barrier coatings. To address this issue, a novel high-entropy Sr(Y_0.2Sm_0.2Gd_0.2Dy_0.2Yb_0.2)₂O₄ ceramic was designed and synthesized for the first time via the solid-state method. It is found that the thermal conductivity of Sr(Y_0.2Sm_0.2Gd_0.2Dy_0.2Yb_0.2)₂O₄ is reduced to 1.61 W·m⁻¹·K⁻¹, 53 % lower than that of SrY₂O₄ (3.44 W·m⁻¹·K⁻¹) at 1500 °C. Furthermore, reasonable TEC (11.53 ×10⁻⁶ K⁻¹, 25 °C ∼ 1500 °C), excellent phase stability, and improved fracture toughness (1.92 ± 0.04 MPa·m^1/2) remained for the high-entropy Sr(Y_0.2Sm_0.2Gd_0.2Dy_0.2Yb_0.2)₂O₄ ceramic, making it a promising material for next-generation thermal barrier coatings.     

An Exploration of Surface Integrity Remanufacturing for Aeroengine Components

Surface integrity is the major factor impacting on the operation quality, service life and reliability of the aeroengine components. The surface integrity of aeroengine component is damaged by the failures such as crack, deformation, oxidation, corrosion, erosion, and microstructural degeneration. It adopts advanced remanufacturing technologies to restore or improve the surface integrity and regenerate these high value parts. This paper firstly puts forward the concept, namely surface integrity remanufacturing for aeroengine components, and its connotation. The key remanufacturing technologies have been developed to repair the components with surface damages. Ultimately, some application examples of surface integrity remanufacturing technologies as well as their effects in aeroengine maintenance are introduced. The discarded components have been reused and their service lives have been extended and their reliability has been increased by implementing surface integrity remanufacturing. It has realized “The Repaired Components Outpacing the New Ones”, material saving, energy saving, and emission reduction.     

Experimental and computational studies on propane-propylene separation by adsorption and variable-temperature stepwise desorption

An experimental adsorption and desorption study was carried out using propane-propylene gas mixtures adsorbed onto 13X molecular sieves in order to obtain a better understanding of a variable-temperature stepwise desorption (VTSD) method that has been found to have potential for industrial separations. The experimental conditions used were based on estimates of possible industrial importance. Both desorption rates and desorption equilibrium data were obtained at one atmosphere with no dilution gases, in small U-tube columns (0.012 m diameter). The desorption rates appeared to be relatively rapid and not an important factor in pilot-scale desorption in comparison with heat transfer rates. A computational method has been developed in order to calculate the composition and amounts of gases that are desorbed during variable-temperature stepwise desorption. The computed predictions ofa pilot-scale system, based on equilibrium data from small scale column experiments, were compared with pilot-scale (0.04 m diameter × 1.8 m length) experimental results and were found to provide reasonable approximations.     

Pressureless consolidation of boron nitride fiber ceramics via a chemical bonding approach

Hexagonal boron nitride (h-BN) materials with excellent physicochemical stability and processibility have been considered as promising engineering materials. However, their practical applications are rather limited by the difficulty in constructing the well-bonded h-BN ceramic. Herein, we present a reaction welding strategy for facile preparation of well-bonded h-BN fibers (BNFs) network by using ethanolamine (ETA) containing alcoholic hydroxyl and primary amine groups as crosslinking agent. The formed >B-O-H₂C-H₂C-H₂N|→B< bond bridges through the esterification and intramolecular coordination (N|→B) reactions between ETA molecules and BNFs containing surface hydroxyls, play an essential role in the construction of the thermodynamically stable >B-N-B< covalent bond between BNFs. Based on this synthetic strategy and a room-temperature molding process followed by a calcination step, a series of resilient BNFs ceramics with high processibility, typical diamagnetism, low dielectric constant (∼ 2.1) and loss, good resistance to temperature different, corrosion, oxidation and abrasion are produced. Besides, they also exhibit excellent strain and damage tolerance, the maximum compression strain and strength can reach up to 38% and ∼ 33 MPa, respectively. Significantly, the deliberately designed BNFs vessel can be successfully used for the alloying of high melting point metals, showing both structural/chemical robustness and good reusability. This ingenious design for well-bonded BNFs network not only is a good model for exploring the welding way for h-BN powders, but also opens up numerous opportunities for practical applications.     

Chemical compatibility of Al2O3-added glass sealant with bare and coated interconnect in oxidizing and reducing environments

Chemical compatibility in oxidizing and reducing environments between sealants and interconnects for planar solid oxide fuel cells (SOFC) are investigated. (Co,Mn)₃O₄, Co-Mn, and Al coatings were prepared on the FeCr-based ferritic-stainless-steel (SUS430). The (Co,Mn)₃O₄ coating exhibited water vapor bubble formation at the outer sealing edges when exposed to H₂, indicating reactions between the coating and sealant. Co-Mn metal coating was found readily oxidized in an oxidizing environment. The glass with 5 wt% Al₂O₃ addition helped mitigate the Cr diffusion into sealant based on bare SUS430 substrate. Moreover, the Al metal layer effectively blocked the diffusion of Cr into the sealant at the interface and environment for 100 h, with a thickness of only 1 µm. At the constant discharge current of 24 A, the voltage is stabilized at about 4.2 V for 48 h using H₂ as fuel gas in 5-cell stack.