HP40Nb钢热浸镀Al-Si高温氧化行为及组织研究

为提高高温抗氧化性能,对HP40Nb钢进行了热浸镀Al-10%(质量分数)Si,并进行不同温度扩散处理,研究了不同扩散处理试样在1000℃条件下的高温氧化行为,通过SEM,EDS和XRD分析了经不同扩散处理后的渗层在高温氧化过程中的组织结构变化.结果表明:经800℃/4h扩散处理,渗层由内层(NiAl+ Cr3 Si)...     

电弧离子镀AlYSi涂层抗高温氧化性能研究

采用电弧离子镀技术在K465镍基高温合金基材上制备了AlYSi沉积-扩散型涂层,研究了K465合金和AlYSi涂层在1100℃下的高温氧化行为.利用SEM,EDX,XRD对氧化后的涂层表面和截面进行分析,结果表明:AlYSi涂层主要由β-NiAl相组成,氧化过程中涂层表面形成了Al2O3保护膜,显著提高了合金的抗高温氧...     

Benefits of Zr addition to oxidation resistance of a single-phase (Ni,Pt)Al coating at 1373 K

A single-phase (Ni,Pt)Al coating with lean addition of Zr was prepared by co-electroplating of Pt-Zr composite plating and subsequent gaseous aluminization treatments. Isothermal and cyclic oxidation behavior of the Zr-doped (Ni,Pt)Al coating samples was assessed at 1373 K in static air in comparison with plain nickel aluminide (NiAl) and normal (Ni,Pt)Al coatings. Results indicated that Zr-doped (Ni,Pt)Al coating demonstrated a lower oxidation rate constant and reduced tendency of oxide scale spallation as well as surface rumpling, in which the enhanced oxidation performance was mainly attributed to the segregation of Zr at oxide scale grain boundaries and the improved Young’s modulus of the coating. Besides, the addition of Zr effectively delayed oxide phase transformation of Al₂O₃ from θ phase to α phase in the early oxidation stage and coating degradation of β-NiAl to γ'-Ni₃Al in the stable oxidation stage.     

Thermal stability of a platinum aluminide coating on nickel-based superalloys

An investigation was carried out to determine the thermal stability of a platinum aluminide coating on the directionally solidified alloy MAR M 002 and its single-crystal version alloy, SRR 99, at 800, 1000 and 1100°C. The morphology, structure and microchemical composition of the coating were characterized using scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. In the as-deposited condition, the coating was found to consist of two layers. Most of the platinum was concentrated in the outer coating layer which consisted of a fine dispersion of PtAl₂ in a matrix of β-(Ni, Pt)Al containing other elements in solid solution, such as cobalt and chromium. The inner coating layer was relatively free of platinum and consisted essentially of β-NiAl. Exposure at 800°C was found to have no significant effect on the structure and composition of the coating on each alloy. At temperatures ?1000°C, however, PtAl₂ became thermodynamically unstable and significant interdiffusion occurred between the coating and alloy substrate. After exposure at 1000°C, the components of the outer coating layer were NiAl and Ni₃Al. However, after exposure at 1100°C, the outer coating layer consisted only of Ni₃Al. Also, after exposure at both temperatures, the composition of the outer coating layer approached that of the inner layer due to interdiffusion. Although the coating on both alloys exhibited similar structural stability at all temperatures investigated, the coating on alloy MAR M 002 was found to develop a more protective scale. This behaviour was correlated with differences in alloy substrate composition particularly rare-earth elements such as hafnium.     

Effect of Nickel Pre-Plated on Microstructure and Oxidation Behavior of Aluminized AISI 316 Stainless Steel

Aluminizing of nickel pre-plated AISI 316 is prepared by a high-activity pack at 1050 °C. The effect of initial nickel layer with different thicknesses on microstructure and oxidation behavior of coating is investigated. After aluminization, the surface microstructure of stainless steel mainly consists of β-(Fe, Ni)Al as matrix with β-FeAl + α -(Fe, Cr) precipitates and an inter-diffusion layer with γ phase. Aluminized coating on specimens with 10 and 20 µm primary thicknesses of the nickel layer includes three layers. The outer zone is made up of β-NiAl thin layer and a β-(Fe, Ni)Al layer. As the nickel layer increases to 50 and 100 µm, aluminide layers consist of outer and inner zone with β-NiAl and Ni₃Al phase, respectively. Oxidation tests at 950 °C show that the oxidation resistance of aluminide coatings improves and oxidation kinetics follows a sub-parabolic rate law by increase in thickness of initial nickel layer.     

Ti6Al4V合金激光原位合成自润滑复合涂层高温摩擦学性能

为提高Ti6Al4V合金的高温摩擦学性能,采用激光熔覆技术在其表面原位合成多相混杂金属基高温自润滑耐磨复合涂层,熔覆粉末的成分为Ni60-16.8%TiC-23.2%WS_2(质量分数,下同),系统地研究复合涂层的显微组织、物相结构及其在20,300,600,800℃下的摩擦学性能和相关磨损机理。结果表明:复合涂层的显微硬度(701.88HV_0.5)约为基体(350 HV_0.5)的2倍;由于原位合成固体润滑相(Ti_2SC/TiS/NiS/TiO/TiO_2/NiCr_2O_4/Cr_2O_3)和硬质相(W,Ti)C_1-x/TiC/Cr_7C_3的协同作用,复合涂层的耐磨减摩性能明显优于基体。随着温度升高,涂层和基体的摩擦因数和磨损率均呈下降趋势,在800℃时复合涂层和基体的摩擦因数分别为0.32和0.43,磨损率分别为1.80×10^-4,2.92×10^-5mm/Nm。在800℃下塑性变形、分层和氧化磨损为基体主要磨损机理,复合涂层以氧化磨损和轻微的黏着磨损为主。     

Influence of Water Vapor on the Isothermal Oxidation Behavior of Thermal Barrier Coatings

The oxidation of specimens with thermal barrier coating (TBC) consisted of nickel-base superalloy, low-pressure plasma sprayed Ni-28Cr-6AI-0.4Y (wt pct) bond coating and electron beam physical vapor deposited 7.5 wt pct yttria stabilized zirconia (YSZ) top coating was studied at 1050℃ respectively in flows of 02, and mixture of O2 and 5%H2O under atmospheric pressure. The thermal barrier coating has relatively low oxidation rate at 1050℃ in pure O2. Oxidation rate of thermal barrier coating in the atmosphere of O% and 5%H2O is increased The oxidation kinetics obeys almost linear law after long exposure time in the presence of 5% water vapor. Oxide formed along the interface between bond coat and top coat after oxidation at 1050℃ in pure O2 consisted of Al2O3, whereas interfacial scales formed after oxidation at 1050℃ in a mixture of O2 and 5%H2O were mainly composed of Ni(AI,Cr)2O4,NiO and AI2O3. It is suggested that the effect of water vapor on the oxidation of the NiCrAlY coating may be attributed     

合金元素在MCrAIY涂层中的行为

采用电弧离子镀在新型γ′-Ni     

Alumina formation and microstructural changes of aluminized CoNiCrAlY coating during high temperature exposure in the temperature range 925°C–1075°C

Abstract

MCrAlY (M = Ni, Co) coatings are commonly used on gas-turbine components as oxidation resistant overlay coatings and bondcoats for thermal barrier systems. In the present work the microstructural features and oxidation behavior of an aluminized Co-base MCrAlY-coating on a Ni-based superalloy have been investigated in the temperature range 925–1075 °C. Microstructural studies of the oxidized coatings by SEM/EBSD were complemented with numerical thermodynamic calculations using the software package ThermoCalc. In the as-received condition the outer part of the coating consisted mostly of β-(Ni,Co)Al. Formation of σ-CoCr was observed at the interface between the β-layer and the inner initial CoNiCrAlY. During high-temperature air exposure alumina based surface scales were formed but the oxidation induced Al depletion of the aluminized coating did not result in formation of the γ’-(Ni₃Al) phase. Rather, the subscale formation of Co/Cr-rich phases was observed and a direct transformation of β- into γ-Ni phase after longer times. It is expected that these subscale microstructural changes thus affect the alumina formation and growth as well as the critical aluminum depletion in a different manner as in the case of corresponding β-NiAl coatings, although a direct comparison between various coating systems was not possible on the basis of the present results.     

Ti0.5Al0.5N涂层的抗高温氧化行为

用AES仪研究了多弧离子镀Ti0.5Al0.5N涂层在空气气氛中的抗高温氧化行为,发现该涂层的抗高温氧化性能极其优异,其最高抗氧化温度可达800C。采用SEM、EDX以及XTEM等方法对Ti0.5Al0.5N涂层的抗氧化机制和氧化失效机理进行了分析。     

Protective Effect of the Sputtered TiAlCrAg Coating on the High-Temperature Oxidation and Hot Corrosion Resistance of Ti-Al-Nb Alloy

The effect of a sputtered Ti-48AI-8Cr-2Ag (at. pct) coating on the oxidation resistance of the cast Ti-46.5AI-5Nb (at. pct) alloy was investigated in air at 1000-1100℃. Hot corrosion in molten 75 wt pct Na2SO4+25 wt pct K2SO4 was investigated at 900℃. The scale on the cast TiAINb tends to spall in air, while the scale on coating is very adherent. The sputtered Ti-48AI-8Cr-2Ag coating remarkably improved high temperature oxidation resistance of the cast Ti-46.5AI-5Nb alloy because of the formation of an adherent Al2O3 scale. Due to the inward diffusion of Cr, Kirkendall voids were found at the coating/substrate interface. TiAICrAg coating provided excellent hot corrosion resistance for TiAINb alloy in molten 75 wt pct Na2SO4+25 wt pct K2S04 at 900℃ due to the formation of a continuous Al2O3 scale.     

Ni-Pd纳米涂层整体式催化剂加氢性能研究

采用浸涂法将自制的介孔空心SiO2纳米粉体涂覆到堇青石基体上,然后采用微波法负载活性组分Pd和助剂Ni制备了纳米涂层整体式加氢催化剂,并考察空速、涂层增重、Ni助剂添加量等因素对其乙炔选择性加氢催化性能的影响。结果表明:经过涂覆后的堇青石整体式催化剂加氢性能与未涂覆时相比有了显著提高,且添加适量的助剂Ni有助于催化性能的进一步改进。在反应温度为54℃、压力为0.1 MPa、空速为3 800 h-1的条件下,使用涂层增重质量分数为6%、Ni与Pd物质的量比为4∶1的催化剂,当乙炔接近完全转化时,乙烯选择性能够到达40.9%。     

Effect of Ru on interdiffusion dynamics of β-NiAl/DD6 system: A combined experimental and first-principles studies

As a diffusion barrier between thermal barrier coating (TBC) and advanced single crystal (SC) superalloy DD6, RuNiAl coating has attracted increasing attention recently. In this work, different diffusion couples including NiAl/DD6, RuNiAl/DD6 and RuAl/DD6, were prepared and their interdiffusion behavior was investigated at 1100 °C, to understand the diffusion barrier mechanism of the RuNiAl coating. The addition of Ru to NiAl effectively reduced the interdiffusion coefficient of Al, thereby delaying the phase transformation from β to γ′ and suppressing the formation of topologically closed-packed (TCP) phases and primary interdiffusion zone (IDZ). It is verified by first-principles calculations that Ru restrained the formation of Ni and Al vacancies and Ni and Al antisite atoms. According to the calculations, the addition of Ru increases the defect formation energies, thus inhibiting the diffusion of Al in β-NiAl. The calculation results are consistent with the experimental data.     

磁控溅射TiAlSiN膜的抗氧化性能

目前,针对TiAlN和TiAlSiN薄膜在800~1 000℃高温氧化时的硬度及抗氧化性能研究较少。利用磁控溅射技术,在高速钢W18Cr4V表面制备了TiAlN和TiAlSiN薄膜,当Al靶功率为100 W、Si靶溅射电流为0.20 A时,TiAlSiN薄膜硬度及弹性模量达到最大值,对此条件下的膜层进行了大气高温氧化试验。采用激光共聚焦显微镜、扫描电子显微镜(SEM)和能谱仪(EDS)、X射线衍射仪(XRD)等检测手段,研究了800,900,1 000℃下2种薄膜的抗氧化性。结果表明:经相同温度氧化处理后,TiAlSiN薄膜的表面粗糙度明显小于TiAlN薄膜的;在TiAlN中引入Si元素形成Si3N4包裹TiN纳米晶的复合结构,抑制了膜层中裂纹的形成,使TiAlSiN薄膜在相同氧化温度下的抗氧化性能比TiAlN薄膜更加优异。     

Role of Y4Al2O9 in High Temperature Oxidation Resistance of NiCoCrAlY-ZrO2.Y2O3 Coatings

NiCoCrAlY-ZrO2·Y2O3 coatings were deposited on the substrates by using a technology of combining electron,atom and ion beams （three beams）. Isothermal oxidation for these samples was performed at 1100℃ for 100-300 h. The results show that a thermally grown oxide （TGO） layer was formed between NiCoCrAlY layer and oxidation. The TGO contains α-Al2O3 and Y4Al2O9 etc. oxides. The intensity ratio of α-Al2O3/Y4Al2O9 was monotonously decreased with increasing oxidation time based on XRD （X-ray diffraction） analysis. The Y4Al2O9 phase plays the most important role in high temperature oxidation resistance at 1100℃. The related mechanism was also discussed.     

Thermal cycling behaviour of thermal barrier coating systems based on first- and fourthgeneration Ni-based superalloys

Abstract

This study deals with the cyclic oxidation behaviour of thermal barrier coating systems. The systems consist of an yttria-stabilised zircona ceramic top coat deposited by EB-PVD, a β-(Ni,Pt)Al bond coat and a Ni-based superalloy. Two different superalloys are studied: a first-generation one and a fourthgeneration one containing Re, Ru and Hf. The aim of this work is to characterise the microstructural evolution of those systems and to correlate it to their resistance to spallation. Thermal cycling is carried out at 1100°C in laboratory air, with the number of cycles ranging between 10 and 1000. Each cycle consists of a 1 h dwell followed by forced-air cooling for 15 min down to room temperature. Among the main results of this work, it is shown that the MCNG-based system is significantly more resistant to spallation than the AM1-based one. Up to 50 cycles, both systems exhibit similar oxidation rate and phase transformations but major differences are observed after long-term ageing. In particular, a Ru-rich β-phase is formed in the bond coat of the MCNG-based system while the AM1- based one undergoes strong rumpling of the TGO/bond coat interface due to the loss of the thermal barrier coating.     

激光熔覆Ni3Al基复合涂层的氧化行为

对比研究了900℃时45号钢,1Cr18Ni9Ti不锈钢和激光熔覆Ni3Al基复合涂层在空气环境下的氧化动力学曲线;采用扫描电镜,X射线衍射技术分析了氧化前后涂层及界面处的微观组织结构。结果表明,激光熔覆层的氧化抗力接近于1Cr18Ni9Ti不锈钢但明显高于45号钢;长时间氧化后涂层组织结构只发生微少的变化,但界面处氧化较严重;激光熔覆层中的氧化产物主要是Al2O3,然后是NiO。     

不锈钢表面阴极微弧电沉积氧化铝膜层的性能

以0.4 mol/L Al（NO₃）₃乙醇溶液为电解液,用阴极微弧电沉积方法在304不锈钢表面制备了80μm厚的氧化铝膜层。分析了膜层的形貌、成分和相组成,测试了膜层的抗高温氧化和电化学腐蚀性能。结果表明.电沉积膜层由γ-Al₂O₃和α-Al₂O₃组成。膜层中含有少量的Fe、Cr、Ni元素,表明膜/基界面附近的不锈钢基体在微弧放电作用下也参与氧化铝膜层的沉积和烧结过程。氧化铝膜层使不锈钢在800℃恒温氧化速率明显降低,表明其抗高温氧化性能得到提高。同时,其腐蚀电位正向移动,腐蚀电流密度降低1个数量级,表明其耐腐蚀性能得到提高。     

ZrO2-C-ZrB2复合材料的氧化动力学

通过差热-热重分析研究了ZrB₂含量为10 %的ZrO₂-C-ZrB₂复合材料在800～1100℃下空气中的氧化动力学,根据气固相反应原理建立氧化动力学模型,计算反应表观活化能,并得到氧化速率与温度的经验关系式。结果表明,试样在 800℃时的氧化过程仅有化学反应控速阶段与化学反应和气体扩散共同作用的混合控速阶段。900～1100℃的氧化过程为前期是化学反应控速阶段,中期为混合控速阶段,后期为扩散控速阶段。三个阶段的表观活化能分别为111.7、71.5和166.0kJ·mol-1 。材料等温氧化的质量变化规律表明在900℃～1100℃内的氧化属于保护型氧化。     

Coatings for protecting nickel-base TaC eutectics against oxidation

A class of very high strength eutectic superalloys consisting of TaC fibers in a γ- Ni/γ'-Ni₃Al matrix is being critically evaluated as a potential turbine blade material. However, the strongest alloys in this system lack the inherent oxidation resistance needed for extended use at 1100°C and above. The present study describes a program aimed at improving oxidation resistance and coating-substrate compatibility for a substrate of a γ/γ'-TaC which has been designated NiTaC- 13.A preliminary study considered seven different electron beam vapor-deposited coating systems of the MCrAlY type (M≡Ni, Co or Fe). The most promising coating was a NiCrAlY composition which showed excellent oxidation resistance; however, during high temperature exposure of all of these coated materials, a region with complete absence of carbide fibers developed in the substrate at the coating-substrate interface.The mechanism of carbide denudation was investigated using samples coated with Ni-20Cr-10Al-lY. It was concluded that a primary cause of fiber denudation was diffusion and dissolution of C in the C-free coating rather than carbon diffusion through the coating with resulting oxidation at the coating-atmosphere interface.NiCrAlY coatings containing C were deposited by several techniques to determine whether C additions would be useful in improving coating-substrate compatibility. The most promising coating was a duplex coating; the first layer of Ni-20Cr-5Al-0.1Y-0.1C was deposited by flame spraying and this was subsequently overcoated with Al. This coating withstood 2000 h of cyclic oxidation with little loss of coating thickness and absence of fiber denudation.Sequential metallographic examinations were made through the 2000 h of testing to show the development of the coating-substrate interactions. Microstructural and phase changes are described and are compared with macrostructural changes and the change in sample weight indicative of oxidation and spallation.