Interacting force estimation during blade/seal rubs

Abradable seals are used in aeronautical compressors to minimize the blade–casing clearance while ensuring the integrity of the mechanical parts in the invent of contact. Considering the tight clearance, in-flight blade–seal interactions may occur and have to be taken into account when designing abradable seals. The blade–seal interacting force is difficult to access but constitutes a key feature to understand the phenomena and to develop numerical models. The present paper aims to present an experimental methodology to estimate the blade–seal interacting force from indirect measurements. The methodology has been applied to a short interaction produced on a dedicated test rig in conditions representative of the full-scale configuration. The obtained force was correlated with the wear profile of the abradable seal.     

Fabrication and characterization of 8YSZ ceramic based abradable seal coatings by atmospheric plasma spraying

8 wt% yttria-stabilized zirconia (8YSZ) powders are fabricated as high-temperature based materials via a solid-state reaction method and ground into spheres in this paper. Following that, 4 wt% Nickle (Ni), 4 wt% Hexagonal Boron Nitride (hBN) and 4 wt% PHB (Polyphenyl ester) are added to 8YSZ for getting 8YSZ ceramic-based abradable seal powders (8YSZ CAS_p). Then, the 8YSZ CAS_p are sprayed on the stainless steel substrate with a NiCoCrAlY transition layer by an atmospheric plasma spraying (APS) technology. The phase structure, surface morphology and the cross-section topography of the fabricated are analyzed, the indentation hardness and nano-indentation test are conducted. The experiments of 8YSZ ceramic-based abradable seal coatings (8YSZ CAS_c) show that the deposition efficiency and porosity are respectively 78.5% and 21.8%, the bond strength is 4.6 MPa, the cycle number of thermal shock resistance is 37 times, those parameters prove that the fabricated 8YSZ CAS_c are promising abradable seal coatings.     

粘结剂对镍基复合粉末及涂层性能影响研究

本文对比分析了四种不同粘结剂制备的镍铬铁铝氮化硼复合粉末及涂层性能, 结果表明： A3 粘结剂的固 化性能和热降解性能与镍铬铁铝氮化硼复合粉末的粉末制备工艺及喷涂工艺匹配性良好, 制备的复合粉末的形貌 和性能较优, 以此制备的封严涂层组织均匀, 硬度为 62 HR15Y, 结合强度为 7.99 MPa, 耐盐浴腐蚀性能良好。     

封严涂层材料及应用

介绍了封严涂层的特点、测试方法、分类以及国内外可磨耗和耐磨封严涂层的应用情况,对部分封严涂层材料的发展过程及涂层的特殊制备工艺进行了阐述。评述了封严涂层的研究现状及在航空工业的发展前景。     

可磨耗封严涂层发展及应用

论述了可磨耗封严涂层的应用特点、国内外现阶段涂层的发展,以及涂层的性能测试方法。其中重点列举了几种可磨耗封严涂层的使用条件及应用部位。     

组元粒度对AlSi包覆BN涂层组织性能的影响

本文制备三种不同粒度配比的AlSi包覆BN复合粉末,通过大气等离子喷涂制备AlSi/BN可磨耗封严涂层,对涂层的硬度,结合强度及涂层组织进行了研究,并通过试验研究了不同形态颗粒在喷涂沉积过程中的演变行为,试验表明,较细的AlSi包覆较小粒径的BN颗粒在喷涂过程中具有最好的沉积效果,BN损失最少,核心BN颗粒粗大的粉末沉积效果差,BN损失严重。     

等离子喷涂 YSZ 可磨耗涂层孔隙率与力学性能关系研究

本文主要研究了多孔 YSZ 可磨耗封严涂层孔隙率与其力学性能的关系。 采用高能等离子喷涂制备了不同 孔隙率自支撑 YSZ 涂层试样, 采用三点弯曲实验研究了孔隙率与 YSZ 涂层室温和 1060 ℃高温力学性能的关系。 结果表明, 涂层孔隙率在 11.61%~28.80% 之间时, 室温下涂层断裂韧性为 12.48 MPa·m1/2~20.96 MPa·m1/2, 抗弯 强度为 17.10 MPa~43.75 MPa, 弹性模量为 3.64 GPa~13.13 GPa, 1060 ℃下涂层断裂韧性为 9.79 MPa·m1/2~13.71 MPa·m1/2, 抗弯强度为 20.20 MPa~35.12 MPa, 弹性模量为 5.15 GPa~11.00 GPa。 随孔隙率增加, 涂层断裂韧性增加, 抗弯强度、 弹性模量减小。 在中、 低孔隙率下, 涂层在高温下的抗弯强度、 弹性模量和断裂韧性低于室温, 在高 孔隙率下, 高温条件下涂层的抗弯强度、 弹性模量高于室温。 随着孔隙率的增加, 高温条件涂层力学性能的变化 趋势相较室温时更为平缓。     

TiAl/BN复合封严涂层的耐腐蚀性能研究

本研究采用大气等离子与真空等离子喷涂技术制备了Al/BN、Ti Al/BN两种金属和陶瓷复合型多孔涂层,用于航空发动机压气机部位的叶尖可磨耗封严。通过电化学测试和盐雾腐蚀实验对两种涂层的盐雾腐蚀性能进行了研究。结果表明,Ti Al/BN涂层的腐蚀电位明显高于Al/BN涂层(约450m V)。同时,在极化曲线测试过程中发现Ti Al/BN涂层出现了明显的钝化现象。经过960h标准盐雾腐蚀试验后,发现Al/BN涂层发生了较严重的腐蚀,而Ti Al/BN涂层仅发生轻微的腐蚀。腐蚀后涂层的XRD分析表明,Ti Al/BN涂层的腐蚀产物主要为Al(OH)3和Al O,没有发现Ti的腐蚀产物。Ti Al/BN复合涂层中形成的Ti Al合金是该涂层比Al/BN涂层更耐中性盐雾腐蚀的原因。     

Composition-structure-property synergistically tailoring of Zr-Y-Ta-O oxides as candidate abradable seal coatings materials

To explore novel abradable seal coatings (ASCs) materials with high working temperatures and excellent performance, we reported the multicomponent Zr-Y-Ta-O oxides with improved properties in ZrO₂-YO_1.5-TaO_2.5 ternary diagram. Six Zr-Y-Ta-O oxides with different components were successfully synthesized by a solid-state reaction, and we elucidated their composition-structure-property relationship. The origins of glass-like thermal conductivity and high toughness were discussed from structural characteristics, and wear resistance was measured by nanoindentation. The high concentration of oxygen vacancies, effective inhibitions of high-temperature thermal radiation, and mitigation of phonon speed simultaneously contributed to the low and glass-like thermal conductivity (1.04–1.43 W·m⁻¹·K⁻¹, 900 ºC). Furthermore, the high thermal expansion coefficients and excellent phase stability indicated that their working temperatures were as high as 1400 °C. The studied Zr-Y-Ta-O oxides can be applied as candidate high-temperature ASCs materials with improved performance.     

Mechanical characterisation of AlSi-hBN, NiCrAl-Bentonite, and NiCrAl-Bentonite-hBN freestanding abradable coatings

This paper reports recent research on abradable materials employed for aero-engine applications. Such thermal spray coatings are used extensively within the gas turbine, applied to the inner surface of compressor and turbine shroud sections, coating the periphery of the blade rotation path. The function of an abradable seal is to wear preferentially when rotating blades come into contact with it, while minimising over-tip clearance and improving the efficiency of the engine.Historically, our understanding of abradables has been limited, with their design and service operation often described as a “black art.” For instance, there is a distinct lack of materials property data for all abradable systems, mainly due to the difficulty of testing this unique class of material under bulk loading conditions (tension or compression).The present paper will describe the mechanical assessment of two families of abradables with either aluminium or nickel as the matrix phase. A novel method was developed to produce the free-standing abradable test specimens, employing thermal spraying and dissolvable moulds. These specimens were suitable for evaluation under static and cyclic tensile stress conditions. The absence of any substrate and associated mechanical interactions has meant that unique measurements of Young's modulus, tensile strength, and strain to failure were obtained for these complex composite materials in their own right.This work forms part of a wider programme to gain a greater understanding of abradable materials, how they perform, and ultimately how to improve their performance in-service.