K38G合金及其溅射微晶层的高温氧化

研究了K38G铸造镍基高温合金及其用平面磁控离广溅射工艺制备的微晶涂层在800-1000℃500小时内的抗高温氧化性。结果表明,微晶化极大改善合金的抗氧化能力,并改变合金表面生成的氧化物类型,由Cr_2O_3变为α-Al_2O_3。还讨论了铸态K38G合金及溅射微晶层的氧化机理。     

LDZ125微晶涂层抗循环氧化性能

研究了高温合金LDZ125及其溅射微晶涂层的抗循环氧化行为.微晶涂层仅由γ相组成,晶粒尺寸约为30nm.结果表明:微晶涂层在1000℃的抗循环氧化性能比铸态合金的有极大提高.微晶层氧化时只形成单一的Al2O3氧化膜,且在整个氧化过程中未见开裂剥落,有极好的粘附性.     

AN INVESTIGATION OF THE OXIDATION AND HOT CORROSION OF A 3SNi-15Cr TYPE IRON-BASE ALLOY

测定了一种35Ni-15Cr型铁基高温合金750—1000℃的氧化动力学曲线,并计算出氧化激活能Q_(p1)=41kcal/g-mol,Q_(p2)=46kcal/g-mol.X射线结构分析表明,氧化膜主要由Cr_2O_3构成,并含有(Cr,Fe)_2O_3,TiO_2及NiCr_2O_4。电子探针分析表明,氧化膜富Cr,Fe,Ti。铬离子在Cr_2O_3中的扩散是这种合金抛物线氧化过程的主要控制机构。 渗铝防护后,氧化膜富Al,Cr,Ti.主要由a-Al_2O_3构成,并含有TiO_2和Fe(Cr,Al)_2O_4。这种致密而牢固的氧化膜使抗氧化和抗热腐蚀性能大为改善。     

一种35Ni-15Cr型铁基高温合金的氧化、腐蚀与防护

测定了一种35Ni-15Cr型铁基高温合金750—1000℃的氧化动力学曲线,并计算出氧化激活能Q_(p1)=41kcal/g-mol,Q_(p2)=46kcal/g-mol.X射线结构分析表明,氧化膜主要由Cr_2O_3构成,并含有(Cr,Fe)_2O_3,TiO_2及NiCr_2O_4。电子探针分析表明,氧化膜富Cr,Fe,Ti。铬离子在Cr_2O_3中的扩散是这种合金抛物线氧化过程的主要控制机构。渗铝防护后,氧化膜富Al,Cr,Ti.主要由a-Al_2O_3构成,并含有TiO_2和Fe(Cr,Al)_2O_4。这种致密而牢固的氧化膜使抗氧化和抗热腐蚀性能大为改善。     

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".     

NiCoCrAlY/Ni-ZrO_2复合热障涂层抗高温氧化性能研究

采用电泳共沉积、真空烧结致密化处理和高速电喷镀工艺,在K17镍基超强耐热合金表面制备NiCoCrAlY/Ni-ZrO_2热障涂层,并进行1000℃抗高温氧化试验。采用SEM、EDS、XRD分析NiCoCrAlY/Ni-ZrO_2热障涂层在高温氧化过程中合金元素的扩散规律。结果表明,NiCoCrAlY/Ni-ZrO_2热障涂层氧化失重为10.1778 mg/cm~2,远低于K17镍基高温合金。在高温氧化过程中生成α-Al_2O_3和Cr_2O_3能提高NiCoCrAlY/Ni-ZrO_2热障涂层的高温抗氧化性。     

FeCrNiAl系高熵合金高温氧化行为及组织演变研究

研究了FeCrNiAl系高熵合金的高温氧化行为,建立了合金的氧化动力学模型,同时借助XRD、SEM和能谱分析,对合金氧化物相结构及形貌和成分进行表征,分析了合金的氧化机理。结果表明合金在800~1000℃都是完全抗氧化的,随着氧化温度的提高,合金氧化速率先增加后减小,1000℃的平均氧化速率小于800℃的平均氧化速率;各个温度下试样单位面积的氧化增重与氧化时间的关系满足抛物线规律,计算得到合金的氧化激活能为167.507 kJ/mol;800℃下枝晶内的氧化产物全部是棒状的金红石结构TiO_2,而枝晶间氧化产物则主要是片层状、紧密相连的Cr_2O_3和TiO_2;900和950℃下形成的氧化膜中主要氧化物均为TiO_2,900℃还含有Cr_2O_3和Fe2O3,950℃氧化膜中还含有α-Al_2O_3。在1000℃合金表面仅形成致密的α-Al_2O_3薄膜,使合金表现出更为优异的抗氧化性能。     

纳米NiCrBSi-TiB_2涂层800℃循环氧化行为研究

采用超音速火焰喷涂技术制备纳米Ni Cr BSi-Ti B_2涂层,对比研究了纳米和微米涂层在800℃下的循环氧化行为。结果表明:纳米涂层表面由完整连续的外层Si O_2膜+内层Cr_2O_3膜构成,细小的Ti O_2颗粒弥散地分布于Si O_2膜上。在800℃循环氧化条件下,纳米涂层氧化增重曲线遵循抛物线规律,扩散机制为该涂层氧化过程中的主要控制步骤。在氧化过程中,纳米涂层表面形成了完整连续的外层Si O_2膜+内层Cr_2O_3膜,同时晶粒细化能够降低涂层内应力,有效地防止涂层开裂,提高了涂层的抗氧化性能。     

Co-20Re-25Cr-1Si合金在0.1 MPa纯O_2中的高温氧化行为

研究了四元Co-20Re-25Cr-1Si合金在1000和1100℃下0.1 MPa纯O_2中24 h的恒温氧化行为。在两个温度下,合金的氧化动力学曲线很不规则,由于表面形成的氧化膜不能阻止合金中Re以ReO_3形式向外蒸发,合金均出现了明显的氧化失重现象。但在1100℃下,合金在氧化初期大约15 min内发生了短暂的持续增重现象;而在1000℃下合金一直处于失重状态。在两个温度下形成的氧化膜非常类似,最外层为较厚的CoO层,次外层为CoO和CoCr_2O_4的混合氧化物,内层为薄且有一定连续性的Cr_2O_3保护层,其下存在着一个Si的内氧化区。由于合金在1000℃下形成的Cr_2O_3保护层更加连续与致密,因此合金在1000℃表现出较好的抗高温氧化性能。     

几种镍基高温合金铝、铬涂层的抗热腐蚀性能

本文对五种高温合金及三种铝、铬涂层,用坩埚融盐全浸法,在700～900℃进行了热腐蚀试验,发现除 GH30外,其余合金上的铝涂层都比铬涂层耐热腐蚀。这可能是因为 Al_2O_3膜比Cr_2O_3 膜致密,且 Cr_2O_3 易与氧离子 O~(2-)反应,生成铬酸盐,Cr_2O_3在融盐中的溶解度也比Al_2O_3大。试验表明,GH30合金上铝涂层抗腐蚀性差是因为βNiAl 相存在大量晶界,产生沿晶内氧化。     

水蒸气对Ni-20Cr合金及其溅射微晶涂层1000℃氧化行为的影响

研究了Ni-20Cr合金及其溅射微晶涂层在1000℃下H     

Investigation of average growth stresses in Cr2O3 scales measured by a novel deflection method

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The mechanism of scale adhesion on sputtered microcrystallized CoCrAl films

The oxidation mechanisms of sputtered microcrystalline Co–30Cr–5Al coatings were investigated by an acoustic emission technique, scatch test, transmission electron microscope (TEM), which was compared with CoCrAlY alloy. The results indicated that the beneficial effects of microcrystallization on the scale adhesion of Co–30Cr–5Al alloy are as follows: (1) The sputtered CoCrAl coating possesses a columnar structure, and oxidation along the columnar grains may form many micropegs which can anchor the scale to the metallic substrate, enhancing bonding of the scale. (2) The grain size of the sputtered coating is several orders of magnitude smaller than that of the cast alloy, and the grain size of oxide scales formed on the former is finer than that of the latter. The finer oxide scale may relieve the growth stresses during isothermal oxidation and partial thermal stresses during cooling by plastic deformation through grain sliding. The microcrystalline coating is more plastic than the cast alloy, which may relieve a certain amount of thermal stresses of the oxide scales. On the basis of oxide adhesion and plasticity, microcrystallization is more beneficial than the addition of reactive elements.     

Rehealing ability of oxide scales formed on microcrystalline K38G coatings

The rehealing ability of the protective oxide scales formed on a microcrystalline coating of the Ni-base superalloy K38G has been studied. The results indicated that the oxide scales on the coating may be rehealed when the original scales are destroyed, and the coating still has excellent resistance against high-temperature oxidation. When the original Al₂O₃ oxide scales spall, mixed-oxide scales of both (Al, Cr)₂O₃ and TiO₂ can form on the surface. The mixed scales are very protective and adherent.     

45钢表面Ni20合金激光熔覆层的组织及抗高温氧化性能

利用激光熔覆技术在45钢表面制备了Ni20合金熔覆层,研究了涂层的相组成、组织结构及抗高温氧化性能。结果表明:熔覆层与基体形成了良好的冶金结合;熔覆层组织具有定向凝固特征,且晶粒生长方向垂直于界面,主要由CrNiFeC,Fe3Ni2,Ni3Cr2等相组成;Ni20合金熔覆层在高温氧化时形成了致密的氧化膜,因而提高了基体材料的抗高温氧化性能。     

钛合金表面激光熔敷Cr13Ni5Si2基金属硅化物涂层组织与耐磨性

以Cr-Ni-Si合金粉末为原料、利用激光熔敷技术在钛合金表面上制得了Cr13Ni5Si2基金属硅化物冶金涂层，在于滑动磨损条件下测试了该涂层的耐磨性能。结果表明，激光熔敷Cr13Ni5Si2基金属硅化物涂层组织主要由Cr13Ni5Si2初生树枝品及少量Cr13Ni5Si2／Cr13Ni5Si2共晶组成，涂层在干滑动磨损条件下具有优异的耐磨性能。     

Beneficial Effects of Ce Implantation into Preformed Cr2O3 Scales on the Subsequent Oxidation of Ni–20Cr Alloy

The influence of Ce implantation into preformed Cr₂O₃ scales with a dose of 1 × 10¹⁷ ions/cm² on the subsequent oxidation behavior of Ni–20Cr alloy at 1050°C in air has been investigated. The pre-oxidation was carried out at 1050°C in air for 0.5 and 1 hr respectively Cr₂O₃ and NiCr₂O₄ formed on Ni–20Cr alloy. The oxidation rate was decreased remarkably due to Ce implantation regardless of whether it was implanted into the alloy or into the pre-formed oxide scales, and the beneficial effect decreased with increasing pre-oxidation time, the alloy implanted directly with Ce had the lowest oxidation rate constant. During cyclic oxidation (350 cycles) Ce implantation played a similar benefical effect on the oxide-spallation resistance for blank and pretreated alloys. The result indicates that Ce incorporated into the oxide scale affected the diffusion of the reaction species and also the spallation resistance of the oxide scales. The change of the oxidation process is attributed to the segregation of Ce at the oxide grain boundaries     

磁控溅射Ni_3(AlCr)微晶涂层的抗氧化性能

研究了铸态Ni3(AlCr)合金及其微晶溅射涂层在900—1000℃下的高温氧化性能,结果表明:铸态Ni3(AlCr)合金在氧化过程中,开始形成以Al2O3为主含有少量NiAl2O4的氧化膜,但氧化膜的粘附性很差,在冷却时很容易剥落,在继续氧化过程中合金表面将形成NiO膜,由于NiO的保护性较差,合金表现出“失稳氧化”行为。而溅射微晶Ni3(AlCr)涂层表面形成的氧化膜与基体粘附良好,冷却过程中未发生剥落。长时间氧化后表面氧化膜只由Al2O3和NiAl2O4组成,未出现NiO,因此溅射微晶化合金的抗氧化     

Oxidation Behaviour of NiCrAl and NiCoCrAl Bond Coatings Under Industrial Gas Turbine Conditions

Model bond coatings were deposited with a wide range of compositions and their oxidation behaviour investigated at 900 °C. These Ni–Co–Cr–Al coatings were deposited using magnetron sputtering (a physical vapour deposition technique) onto 10 mm diameter sapphire substrates. A range of compositions was generated by co-sputtering from a combination of two or three sources: Ni–10 wt% Cr, Ni–20Cr, Ni–50Cr, Ni–20Co–40Cr and/or Ni–40Co–20Cr combined with pure Al. The coatings were oxidised at 900 °C and the scales formed characterised. These data have been summarised into oxide predominance diagrams to show the relationships between coating compositions and the formation of protective Cr₂O₃ or Al₂O₃ scales, or the formation of other, less protective oxides (or mixed oxides). Both coating composition and exposure temperature (by comparison with earlier published research) were found to influence the oxide scale growth rate and oxide type, and thus the resulting degree of protection.     

Comparison of oxidation behavior of Ni–20Cr alloy and Ni-base self-fluxing alloy during air plasma spraying

Oxidation behavior of Ni–20Cr alloy and Ni-base self-fluxing (NiCrSiBC) alloy in atmospheric plasma spraying was studied experimentally. The in-flight particles were collected by quenching into liquid nitrogen. The oxygen contents in the collected particles and the coatings deposited on a substrate were analyzed by the inert gas fusion method. The oxide distribution, morphology and phase composition were analyzed using SEM, EDX, XRD, and AES. The results clearly show that the oxygen content in the NiCrSiBC coating was remarkably lower than that in the Ni20Cr coating by a factor of over 10. The formation of Cr₂O₃ and its vaporization primarily occurred during the flight of Ni20Cr particles, which dominated the oxidation in the coating. In contrast, little oxygen pickup occurred during flight for the NiCrSiBC alloy particles and a thin surface layer of 5 nm with rich in oxygen was found on the surface of NiCrSiBC splats. The mechanism of protecting NiCrSiBC alloy particles from oxidation is preferential oxidation of C, Si and B and simultaneous vaporization of the formed oxides.