Fe20Cr4.5Al微晶和含Y2O3弥散氧化物微晶涂层的高温氧化性能

采用自行研制的高频电脉冲沉积(HFESD)设备在Fe20Cr4.5Al合金表面分别制备了Fe20Cr4.5Al微晶涂层与Fe20Cr4.5Al-Y2O3弥散氧化物微晶涂层.在1000℃和1100℃静态空气中,对合金基体和施加涂层试样进行了200 h的恒温氧化实验.结果表明在两种实验温度条件下,含有Y2O3弥散氧化物颗粒的微晶涂层,完全消除了Al2O3氧化膜中的凸脊,细化了氧化膜的晶粒,抑制了氧化膜的剥落,大大地提高了氧化膜的致密性和粘附性.单一的微晶涂层则部分抑制了凸脊状氧化膜的形成,氧化膜由脊状氧化物和细晶氧化物混杂组成.涂层对氧化增重的影响则与氧化温度-氧化膜的生长速率有关,在1000℃下,涂层试样的氧化增重均有所降低,其中弥散氧化物微晶涂层试样的氧化增重最低;在1100℃下,施加微晶涂层和弥散氧化物涂层对氧化增重影响很小.微晶和Y2O3弥散氧化物颗粒在提高Al2O3氧化膜保护性方面具有"协同效应".     

Fe20Cr4.5Al微晶和含Y2O3弥散氧化物涂晶涂层的高温氧化性能

采用自行研制的高频电脉冲沉积（HFESD）设备在Fe20Cr4.5Al合金表面分别制备了Fe20Cr4.5Al微晶涂层与Fe20Cr4.5Al-Y2O3弥散氧化物微晶涂层。在1000℃和1100℃静态空气中，对合金基体和施加涂层试样进行了200h的恒温氧化实验。结果表明：在两种实验温度条件下，含有Y2O3弥散氧化物颗粒的微晶涂层，完全消除了Al2O3氧化膜中的凸脊，细化了氧化膜的晶粒，抑制了氧化膜的剥落，大大地提高了氧化膜的致密性和粘附性。单一的微晶涂层则部分抑制了凸脊状氧化膜的形成，氧化膜由脊状氧化物和细晶氧化物混杂组成。涂层对氧化增重的影响则与氧化温度－氧化膜的生长速率有关，在1000℃下，涂层试样的氧化增重均有所降低，其中弥散氧化物微晶涂层试样的氧化增重最低；在1100℃下，施加微晶涂层和弥散氧化物涂层对氧化增重影响很小。微晶和Y2O3弥散氧化物颗粒在提高Al2O3氧化膜保护性方面具有“协同效应”。     

Ni-20Cr-Y_2O_3弥散氧化物微晶涂层及其高温氧化性能

采用高频电脉冲沉积技术在Ni 2 0Cr合金表面上沉积MGH75 4ODS合金 ,获得了Ni 2 0Cr Y2 O3 弥散氧化物微晶涂层。在 10 0 0℃空气中对Ni 2 0Cr合金及施加涂层的试样进行 10 0h的氧化实验。结果表明 ,微晶化和添加弥散氧化物 (Y2 O3)促进了铬发生选择氧化形成Cr2 O3 氧化膜 ,提高了合金的抗高温氧化性能和氧化膜的粘附性。用AFM ,SEM ,EDS和XRD分别对Ni 2 0Cr合金与Ni 2 0Cr Y2 O3 弥散氧化物微晶涂层的形貌、结构和成分进行了研究 ,讨论了弥散氧化物微晶涂层改善Ni 2 0Cr合金高温氧化性能的协同作用机理。     

高频电脉冲沉积铝化物微晶涂层的氧化行为

采用新型高频电脉冲沉积技术在１Ｃｒ１８Ｎｉ９Ｔｉ不锈钢表面上获得了晶粒尺寸约为几十到几百纳米的微晶铝化物涂层。在１０００℃空气中恒温氧化１００ｈ的实验结果表明：获得的铝化物微晶涂层具有优异的抗高温氧化性能,而且显著提高了氧化膜的抗剥落能力。施加铝化物涂层后,１Ｃｒ１８Ｎｉ９Ｔｉ不锈钢的氧化膜由以Ｆｅ的氧化物为主转化为以Ａｌ的氧化物为主。由于材料表面的铝化物涂层为微晶层,提高了Ａｌ的选择氧化能力和氧     

微晶Ni3Al高温氧化的动力学规律

对比研究了Ｎｉ３Ａｌ微晶处理前后在１０００℃氧气中高温氧化的动力学规律。研究结果表明,微晶化处理后,合金氧化速率显著降低,抗氧化性能大大提高;微晶Ｎｉ３Ａｌ氧化动力学规律与Ｗａｇｎｅｒ高温氧化抛物线规律相比,具有明显的负偏差。由于微晶化后形成的氧化膜是微晶,晶界密度极大增加,短路扩散远远大于晶格扩散,根据多维缺陷对氧化动力学的影响规律,并考虑氧化物晶粒长大动力学,推导出微晶氧化动力学服从四次方规律ｘ４＝ｋｐｔ,实验结果与推导结果符合得非常好。     

高温合金微晶涂层上氧化膜的修复性

本文研究了一种镍基高温合金K38G的微晶涂层上保护性氧化膜的修复性。结果表明,溅射微晶涂层上的氧化膜有优良的修复性,氧化膜剥落后,涂层仍具有优良的抗高温氧化性能。氧化膜局部小范围剥落后,表面仍能生成单一的Al_2O_3,氧化膜。氧化膜大面积剥落后,虽然生成由(Al、Cr)_2O_3与TiO_2组成的复合外氧化膜,但它具有优良的防护性和粘附性。     

单晶Ni—6.0Al—6.5Ta—8.5Mo—6.5Cr合金的高温氧化及其氧化物分布特征

对单晶Ni-6.0Al-6.5Ta-8.5Mo-6.5Cr合金高温氧化后的组织结构进行了SEM观察,并用EDAX和X射线衍射对其氧化物进行分析,研究了合金氧化物的分布特征及其对持久性能的影响。结果表明：在大气环境的服股条件下无保护涂层合金的表层、次表层发生明显的氧化、内氧化现象;在氧化初期形成以Al为主的氧化物,在近表层处形成以Cr,Al和Ta为主的氧化物,在次表层形成的大颗粒内氧化物为α-Al2O3,Mo不参与合金的内、外氧化,近内氧化物处出现贫Al区,致使区为γ强化相消失;有保护涂层的单晶合金高温氧化后,贫Al区尺寸减小,区内无大尺寸内氧化物,因此使合金的持久性能明显提高。     

NiAl微晶涂层对NiAl-TiC复合材料高温氧化性能的影响

研究了磁控溅射ＮｉＡｌ微晶涂层对ＮｉＡｌ－ＴｉＣ（２０％,体积分数）复合材料１０００－１１００℃高温氧化性能的影响。结果表明,ＮｉＡｌ微晶涂层大大提高了ＮｉＡｌ－ＴｉＣ复合材料的恒温及循环氧化性能,降低氧化速率几个数量级,对于ＮｉＡｌ－ＴｉＣ复合材料来说,其表面形成以ＴｉＯ２为主的复合氧化物,而施加ＮｉＡｌ微晶涂层后,其表面氧化物主要是Ａｌ２Ｏ３。     

溅射LDZ125微晶涂层抗高温氧化行为

研究了镍基高温合金ＬＤＺ１２５溅射微晶涂层的氧化行为。微晶涂层仅由γ相组成,晶粒尺寸小于１００ｎｍ。微晶涂层在１０００℃的抗氧化性能比由γ,γ‘及碳化物组成的铸态合金有明显提高。     

K17F微晶涂层氧化膜的修复性

研究了高温合金Ｋ１７Ｆ溅射微晶涂层的氧化膜的修复性。     

Oxidation and interfacial fracture behaviour of NiCrAlY/Al2O3 coatings on an orthorhombic-Ti2AlNb alloy

Al₂O₃ diffusion barriers of various thicknesses have been fabricated by filtered arc ion plating between the NiCrAlY coating and the O-Ti₂AlNb alloy. Isothermal oxidation tests and three-point bend tests have been conducted to investigate the influence of the Al₂O₃ diffusion barriers on the oxidation and interfacial fracture behaviour of the coatings. The results indicate that the Al₂O₃ diffusion barrier defers interdiffusion and gives oxidation resistance of the NiCrAlY coatings. The thickness of the Al₂O₃ interlayer not only influences the oxidation behaviour but also affects the interfacial fracture properties. Additionally, thermal exposure affects the critical load in three-point bend tests.     

Thermal cycle behavior of plasma sprayed La2O3, Y2O3 stabilized ZrO2 coatings

The effects of La₂O₃ addition on thermal conductivity, phase stability and thermal cycle life of Y₂O₃ stabilized ZrO₂ plasma sprayed coatings were investigated. Although low thermal conductivity as well as high resistance to sintering was achieved by La₂O₃ addition, it tended to also result in lower phase stability and thermal cycle life of the coatings. Optimization of the composition and structure of the coatings improved these properties, and the optimized coatings showed prolonged thermal cycle life.     

MoS2 coated with Al2O3 for Ni-MoS2/Al2O3 composite coatings by pulse electrodeposition

The MoS₂ powders were coated with Al₂O₃ (5 wt.%) through controlling hydrolysis of Al (NO₃)₃·9H₂O. MoS₂ powder coated with Al₂O₃ was written as MoS₂/Al₂O₃ hereinafter. MoS₂/Al₂O₃ powders were put into Ni plating electrolyte bath. Cetyltrimethylammonium bromide (CTAB) — the surfactant was also put into the bath. The experiment proves that MoS₂/Al₂O₃ particles were absorbed onto the Ni plate. The amount of MoS₂/Al₂O₃ deposited on Ni plate rises with the increasing concentration of MoS₂/Al₂O₃ in the bath. The microhardness, micro-surface, phase and the tribological property of the MoS₂/Al₂O₃ multi-plating coating were measured and analyzed. The performances of microhardness and wear resistance of the Ni-MoS₂/Al₂O₃ composite are better than those of Ni-MoS₂ composite.     

Development of moderate temperature CVD Al2O3 coatings

Chemically vapor deposited Al₂O₃ coatings, due to their high hardness and chemical inertness, are currently the state of art in the cutting tool industry. The conventional high deposition temperature of about 1050 °C for Al₂O₃ coatings, based on the water–gas shift process, has to a great extend restricted the development of several hybrid coatings, such as TiC/TiN/TiCN/Al₂O₃. To overcome this limitation, alternate systems to deposit Al₂O₃ at moderate temperatures have been investigated. Systems using NO–H₂, H₂O₂, NO₂–H₂ and HCOOH were identified and thermodynamic calculations were performed to evaluate them as potential sources of oxygen donors to form Al₂O₃ in the moderate temperature range of 700–950 °C. Preliminary results have clearly demonstrated that it is possible to grow moderate temperature alumina (using such alternate sources) on the TiC/TiN coated cemented carbide substrates.     

CeO2掺杂对ZrO2-Y2O3纳米涂层性能的影响

在45钢基体表面等离子弧喷涂制备了掺杂不同含量CeO2纳米ZrO2涂层,运用XRD,SEM对涂层的组织结构进行了分析,测试了涂层的结合强度和显微硬度,考察了涂层与铝青铜对磨时的摩擦磨损性能．结果表明,CeO2增加了ZrO2涂层的致密性、结合强度和显微硬度．纳米ZrO2涂层中加入CeO2后,增加了ZrO2涂层／铝青铜摩擦副的摩擦系数,增强了纳米ZrO2涂层,耐磨能力．涂层与铝青铜对磨时,随着CeO2含量的增加,ZrO2涂层粘着磨损形式增强,而涂层脆性断裂脱落的趋势减轻．     

Mechanical properties of the plasma-sprayed Al2O3/ZrSiO4 coatings

The mechanical properties of plasma-sprayed Al₂O₃/ZrSiO₄ coatings were investigated by indentation-based techniques. Two types of feedstock were used to prepare the coatings: spray-dried powders and plasma-spheroidized powders. A 100-kW direct current (d.c.) thermal plasma system was employed. The values obtained were found to exhibit a close relationship with the microstructure of the as-sprayed coatings, which composed of zircon, alumina, amorphous silica and tetragonal zirconia. The coatings produced with plasma-spheroidized powders had higher microhardness, Young's modulus and fracture toughness than that produced with the spray-dried powders. The coatings produced with plasma-spheroidized powders by a 100-kW computerized system at 15 kW of net plasma energy had the best mechanical properties, while those deposited at 19 kW of net plasma energy had the worst properties due to the high density of cracks in the coatings.     

Thermal conductivity and thermal cycle life of La2O3 and HfO2 doped ZrO2-Y2O3 coatings produced by EB-PVD

The effects of La₂O₃ and HfO₂ addition on thermal conductivity and thermal cycle life of EB-PVD YSZ coatings were investigated. La₂O₃ and HfO₂ were selected as additives, because they significantly suppress the sintering of YSZ. The developed coating showed low thermal conductivity as well as high resistance to sintering. Burner rig tests confirmed that the developed coating have a superior thermal insulating effect and have a longer life than that of a coating with conventional composition.     

Corrosion behaviour of Y2O3-ZrO2 coatings on IN713LC in a LiCl-Li2O molten salt

Hot corrosion studies were performed on superalloy specimens. The IN713LC superalloy were sprayed with an aluminized NiCrAlY-bond coat and then with an yttria-zirconia top coat. The bare superalloy reveals an obvious weight loss due to spalling of the scales by the rapid scale growth and thermal stress. The top coatings showed a much better hot corrosion resistance in the presence of LiCl-3 wt.% Li₂O molten salt when compared with those of the bare superalloy and the aluminized bond coatings. These coatings have been found to be beneficial for increasing hot corrosion resistance of structural materials for lithium molten salts.     

Thermodynamics and phase diagrams in the binary systems Na2O-SiO2, Na2O-GeO2, Na2O-B2O3, Li2O-B2O3, CaO-B2O3, SrO-B2O3, and BaO-B2O3

We applied our model to the enthalpy of mixing data of the binary systems Na₂O-SiO₂, Na₂O-GeO₂, Na₂O-B₂O₃, Li₂O-B₂O₃, CaO-B₂O₃, SrO-B₂O₃, and BaO-B₂O₃. The most stable composition in the liquid, that is where the enthalpy of mixing is most negative, is with a metal-oxygen ratio of 4 to 3, for monovalent metals (Na and Li) and 3 to 4 for divalent metals (Ba and Ca) in liquid silicates or borates. The same applies to the CaO-SiO₂, CaO-Al₂O₃, PbO-B₂O₃, PbO-SiO₂, ZnO-B₂O₃, and ZnO-SiO₂ systems. The oxygen to metal ratio, its constant value in various types of systems, reflects and describes the structure of the liquid. Using the analyzed enthalpies of mixing data and the available phase diagrams, we calculated the enthalpies of formation of the various binary compounds. The results are in excellent agreement with data in the literature that were obtained from direct solid-solid calorimetry.