γ-TiAl合金表面Al_2O_3/Al复合涂层的抗高温熔盐腐蚀性能（英文）

采用磁控溅射技术于γ-TiAl合金表面制备Al_2O_3/Al复合涂层。在850℃下、100%(质量分数)Na_2SO_4熔盐中观测Al_2O_3/Al复合涂层的高温腐蚀行为。结果表明,Al_2O_3/Al复合涂层具备由Al_2O_3表层、富Al中间层以及互扩散层组成的梯度结构,因而有效地提高了基体γ-TiAl合金的抗高温腐蚀性能。在腐蚀实验后,涂层试样表面相结构为Al_2O_3、TiO_2和TiAl_3。致密的Al_2O_3/Al复合涂层有效地抑制了O~(2-)、S~(2-)和Na~+对基体γ-TiAl合金的侵蚀。并且,Al_2O_3/Al复合涂层的梯度结构亦使其表现出了优异的抗开裂和抗剥落性能。     

Al-Cr涂层对TC21合金抗氧化和热腐蚀性能的影响

采用双辉等离子表面渗铬和后续多弧离子镀铝处理在TC21合金表面制备Al-Cr涂层;同时研究Al-Cr涂层在850℃下的高温氧化行为和850℃下25%NaCl+75%Na_2SO_4(质量分数)混合盐中的热腐蚀行为。结果表明:Al-Cr复合涂层包括表面富Al沉积层、中间Al-Cr扩散层和内侧Cr-Ti互扩散层。在850℃氧化100 h后,Al-Cr涂层表面生成致密Al_2O_3膜,对基体有很好的保护作用;中间Al-Cr扩散层中Cr元素的存在促进Al的选择性氧化,有利于涂层的后续氧化行为。在850℃混合熔盐中腐蚀100 h后,内部Cr-Ti扩散区仍保持完整,涂层表现出较好的热腐蚀抗力。     

γ-TiAl合金表面Al-Y梯度涂层在850℃硫酸盐中的热腐蚀行为

为了提高γ-TiAl合金的耐腐蚀性,采用磁控溅射技术在其表面制备了Al-Y梯度涂层。利用SEM、EDS和XRD分析了涂层的表面形貌、元素分布及相组成。研究了涂层在850℃Na_2SO_4中的热腐蚀行为,并对其腐蚀机制进行了分析。结果表明:Al-Y梯度涂层由沉积层和扩散层组成,厚度约为55μm,表面致密,无明显的孔洞和裂纹,由表及里Al、Y、Ti元素呈梯度分布;Al-Y梯度涂层表面在850℃Na_2SO_4中生成了Al_2O_3、Y_2O_3等氧化物保护层;涂层中Y元素的存在能阻止S元素从界面薄弱处侵入基体,涂层中形成的Y_3Al_5O_(12)相能有效提高耐腐蚀氧化层与基体之间的结合力。Al-Y梯度涂层在850℃Na_2SO_4中具有较好的抗热腐蚀性能。     

DD98M纳米晶AlSi渗层制备及抗高温腐蚀性能研究

采用磁控溅射技术在DD98M合金表面制备了同成份的纳米晶,采用多弧离子镀技术在DD98M纳米晶涂层表面沉积了AlSi涂层,对上述制备态纳米晶+AlSi复合涂层进行了真空扩散处理,得到了外层为β-NiAl层、内层为γ'-Ni_3Al层的双层结构复合涂层。研究了合金、DD98M纳米晶涂层及复合涂层在1050℃恒温氧化及900℃下Na_2SO_4+25%K_2SO_4混合熔盐体系中的热腐蚀行为。结果表明:1050℃恒温氧化时,DD98M合金表面生成NiO,α-Al_2O_3,Ta_(0.8)O_2,CrTaO_4及NiAl_2O_4等组成的混合氧化物膜,氧化膜开裂剥落严重。纳米晶涂层表面生成α-Al_2O_3和少量NiAl_2O_4组成的混合氧化物膜,复合涂层表面形成了均匀致密的单一α-Al_2O_3膜。纳米晶涂层和复合涂层大幅提高了合金的抗恒温氧化性能。在900℃下Na_2SO_4+25%K_2SO_4熔盐中,DD98M合金20 h后即发生了灾难性腐蚀,沉积态纳米晶及其预氧化涂层提高了合金的抗热腐蚀性能,复合涂层大幅提高了合金的抗热腐蚀性能。     

纳米晶涂层对DD98M合金热腐蚀行为的影响

为了研究纳米化对DD98M合金热腐蚀行为的影响,采用磁控溅射的方法制备了与其成分相同的纳米晶涂层。运用XRD、SEM/EDS、TEM分别分析了涂层的结构和热腐蚀性能。结果表明:沉积态的纳米晶涂层呈柱状晶结构,有大量沿沉积方向的柱状晶界,晶粒宽度为30~100 nm。涂层为单一的γ相且具有明显的(111)择优取向。在900℃Na_2SO_4+25%K_2SO_4以及Na_2SO_4+25%Na Cl盐中,DD98M合金在5 h内就发生了严重腐蚀。纳米晶涂层在熔融Na_2SO_4+25%K2SO4中表现出了良好的热腐蚀性能,但在Na_2SO_4+25%Na Cl盐中,纳米晶及其预氧化涂层对DD98M合金的抗热腐蚀性能的提高并不明显。纳米晶促进了涂层表面Al_2O_3膜在空气中和熔融Na_2SO_4+25%K2SO4盐中的快速形成,显著提高了DD98M合金在硫酸盐中的抗热腐蚀性能,预氧化处理则使涂层的抗热腐蚀能力进一步提高。     

TiAl合金表面搪瓷基复合涂层与多弧离子镀NiCrAlY涂层的抗热腐蚀行为对比研究

以Ti-45Al-2Mn-2Nb合金为基体,采用多弧离子镀制备NiCrAlY涂层、喷涂-烧结法制备搪瓷基复合涂层,对比研究了2种涂层以及合金基体的热腐蚀行为。热腐蚀实验温度为850℃,选用饱和盐溶液溶质成分为75%Na_2SO_4+25%NaCl (质量分数),涂盐量为1.5～2.5 mg/cm~2。研究结果表明,合金基体完全不具备抗热腐蚀能力,表面形成的氧化膜疏松多孔,且极易剥落;NiCrAlY涂层表面生成的保护性Al_2O_3膜提高了合金的抗热腐蚀能力,然而涂层与基体间严重的互扩散及Al_2O_3膜与熔盐的碱性溶解使得NiCrAlY涂层逐渐失效,热腐蚀60 h即出现氧化膜的剥落;而搪瓷基复合涂层在熔盐环境中只发生了轻微的物理溶解,具有极高的热稳定性及较低的热腐蚀速率,有效地阻隔了腐蚀性离子的入侵,抗热腐蚀性能优异。     

Al/Cr复合涂层对Ti2AlNb合金抗热腐蚀性能的影响

目的改善Ti2AlNb合金在高温腐蚀盐环境中的耐热腐蚀性能。方法在Ti2AlNb合金表面通过双层辉光等离子渗铬及磁控溅射镀铝技术制备Al/Cr复合涂层,分析涂层热腐蚀前后的微观形貌和物相组成,并探究涂覆Na2SO4盐膜的试样在不同温度下(750、850、950℃)的热腐蚀行为。结果Al/Cr复合涂层组织均匀致密,且与基体结合良好,厚度约73μm,由表及里依次由Al沉积层、Al/Cr合金层、Cr沉积层、Cr扩散层四部分组成。经不同温度Na2SO4盐热腐蚀后,Al/Cr复合涂层腐蚀程度均显著小于合金基体。涂层试样经750~850℃Na2SO4盐热腐蚀后质量变化较小,850℃腐蚀增重仅0.525 mg/cm^2,而经历950℃、40 h熔盐热腐蚀后失重达到73.571 mg/cm^2,且试样截面出现剥离、脱落现象,Al/Cr复合涂层抵抗热腐蚀能力减弱。结论具有涂层保护的试样抗热腐蚀性能明显优于合金基体。Al/Cr复合涂层在750~850℃Na2SO4盐环境中具有良好的热腐蚀抗力,而更高温度段(850~950℃)的热腐蚀抗力下降。Al/Cr复合涂层在Na2SO4盐环境中良好的抗热腐蚀性得益于涂层中Al、Cr元素氧化形成以Al2O3、Cr2O3为主的混合氧化膜,有效阻碍外界氧气及腐蚀性介质侵入基体。     

渗铝铌合金的微弧氧化及热腐蚀性能

为了优化渗铝铌合金的微弧氧化工艺和了解复合涂层的抗热腐蚀性能,利用粉末包埋渗法在铌合金基体上制备渗铝层,再通过调整微弧氧化电参数以及添加剂Y(NO_3)_3的含量获得Al_2O_3陶瓷膜外层,确定最佳工艺参数。以最佳工艺制备复合涂层(MAO-Y/Al/C103),与不含Y(NO_3)_3制备的MAO/Al/C103进行对比,研究其抗热腐蚀性。结果表明:以微弧氧化膜层的硬度和厚度为主要评价指标,获得最佳参数为电压380 V,频率400 Hz,占空比10%,处理时间30 min。添加Y(NO_3)_3可获得均匀规则的多孔形貌;含与不含Y(NO_3)_3制备的试样相结构一致,都由NbAl_3和γ-Al_2O_3相组成。经900℃混合熔融盐中热腐蚀50 h,MAO/Al/C103和MAO-Y/Al/C103试样都生成Al_2O_3和NaNbO_3相,其热腐蚀增重量分别为55.71 mg/cm~2和45.59 mg/cm~2。MAO-Y/Al/C103试样由于在热腐蚀阶段有更多的NaNbO_3生成以及微弧氧化微孔大幅减小,表现出更优异的抗热腐性。     

Ti_3Al及其渗铝涂层的热腐蚀性能

采用电化学方法并结合各种物相分析技术研究了Ti_3Al金属间化合物在熔融(Na,K)_2SO_4-NaCl中的热腐蚀行为及渗铝涂层对其耐蚀性能的影响。结果表明,Ti_3Al耐热腐蚀性能较差。形成了外层为TiO_2,中间层为富铝的TiO_2-Al_2O_3复合层,内层为富铌的Nb_2O_5-TiO_2-Al_2O_3层的三层结构。渗铝涂层能在合金表面形成Al_2O_3氧化膜而明显改善Ti_3Al的耐蚀性能。     

N_2-O_2-SO_2气氛中沉积盐引起Fe_3Al和FeAl的热腐蚀

研究表面分別有混合盐Na_2SO_4-NaCl,Na_2SO_4-V_2O_5和纯Na_2SO_4沉积并在模拟燃气气氛中Fe_3Al和FeAl于600℃的热腐蚀,在所有试验条件下两种合金均发生热腐蚀。随试验时间的延长、纯Na_2SO_4和Na_2SO_4-NaCI引起的腐蚀明显减缓,而Na_2SO_4-V_2O_5的腐蚀则加剧并长时持续。FeAl一般较之Fe_3AI耐蚀,只有在Na_2SO_4-NaCl情况下两者腐蚀性能相近。所有合金的腐蚀产物层总是由一高铁的外层和含铝与铁和少量硫的内层组成,后者的成分随     

Effects of sulfur pressure on the sulfidation behavior of 310 stainless steel

High-temperature sulfidation behavior of 310 stainless steel was studied over the temperature range of 700–900°C above a pure sulfur pool with the sulfurvapor range of 10^–4–10^–1 atm. The corrosion kinetics followed the parabolic rate law in all cases. The corrosion rates increased with increasing temperature and sulfur pressure. The scales formed on 310 stainless steel were complex and multilayered. The outer scale consisted of iron sulfide (with dissolved Cr), (Fe, Ni)₉S₈ and chromium sulfides (Cr₂S₃ and Cr₃S₄ with dissolved Fe), while the inner layer was a heterophasic mixture of Cr₂S₃, Cr₃S₄, NiCr₂S₄, and Fe₁–_xS. Platinum markers were found to be located at the interface between the inner and outer scales, suggesting that the outer scale grew by the outward transport of cations (Fe, Ni, and Cr), and the inner scale grew by the inward transport of sulfur. The formation of Cr₂S₃, Cr₃S₄, and NiCr₂S₄ partly blocked the transport of iron through the inner scale, resulting in a reduction of the corrosion rates as compared with the results in the literature.     

Effects of Mo and Al Additions on the Sulfidation Behavior of 310 Stainless Steel

The high-temperature sulfidation behavior of 310stainless steel (310SS) with Mo and Al additions (up to10 at.%) was studied over the temperature range700-900°C in pure-sulfur vapor over the range of 10^-3 to 10^-1 atm. Thecorrosion kinetics followed the parabolic rate law inall cases and the sulfidation rates increased withincreasing temperature and sulfur pressure. Thesulfidation rates decreased with increasing Mo and Al contents and it wasfound that the addition of 10 at.% Mo resulted in themost pronounced reduction among the alloys studied. Thescales formed on 310SS with Mo additions were complex, consisting of an outer layer of ironsulfide (with dissolved Cr), (Fe,Ni)₉S₈, andCr₂S₃/Cr₃S₄(with dissolved Fe), and an inner heterophasic layer ofFe_1-xS,Cr₂S₃/Cr₃S₄,NiCr₂S₄,Fe_1.25Mo₆S_7.7, FeMo₂S₄, andMoS₂. The scales formed on 310SS with Mo andAl additions had a similar mixture as above, except thatAl_0.55Mo₂S₄ was alsoobserved in the inner layer. The formation ofMoS₂ andAl_0.55Mo₂S₄ partly blocked the transport of cations throughthe inner scale, resulting in the reduction of thesulfidation rates compared to 310SS.     

LaSrCuO4粉体微结构对Ag/LSCO电接触材料性能的影响

以硝酸镧、硝酸铜、硝酸锶等为原料,分别采用固相法、溶胶-凝胶法和共沉淀法合成了不规则颗粒状(LSCO_g)、介孔状(LSCOm)和片层状(LSCOl)的LaSrCuO_4(LSCO)粉体。采用高能球磨并结合初压-初烧-热压工艺制备出Ag/LSCO电接触材料。利用X射线衍射(XRD)、扫描电镜(SEM)、金属电导率仪、维氏硬度计和电寿命试验机等对粉体形貌及电接触材料的物理和电学性能进行了表征。结果表明:与Ag/LSCO_(m)、Ag/LSCO_l材料相比,Ag/LSCO_(g)电接触材料表现出更加优异的物理性能,其电阻率为2.37μΩ·cm,硬度为800MPa,密度为9.32g/cm~3;但电学性能差异较小,其在AC220V12A开断状态下的燃弧能量为400 mJ、燃弧时间为23 ms,关合状态下的燃弧能量为1500 mJ,燃弧时间为68ms。Ag/LSCO电接触材料的主要失效形式是液滴喷溅,微裂纹和孔洞。     

不同催化剂对镁合金表面SiO_2-ZrO_2涂层耐蚀性的影响

镁合金表面溶胶凝胶涂层存在易析出氢气、涂层缺陷多及防腐性能提升不明显等问题。为改善这些问题利用Ce(NO_3)_3催化制得SiO_2-ZrO_2溶胶并旋涂3层于AZ91D镁合金表面,并与HCl催化制得的镁合金表面SiO_2-ZrO_2溶胶涂层进行对比分析。采用扫描电镜和傅里叶红外光谱等分析涂层微观形貌和化学成分;通过接触角测试涂层亲疏水性;利用极化曲线和电化学阻抗谱对比研究不同催化剂加入的溶胶凝胶层在3.5%NaCl溶液中的耐腐蚀性能。结果显示:与HCl催化制得的镁合金表面SiO_2-ZrO_2溶胶涂层相比,Ce(NO_3)_3催化制得的涂层表面微观缺陷少;接触角由84.2°增大到93.5°;同镁合金基体自腐蚀电流密度1.480×10~(-4) A/cm~2相比,HCl催化和Ce(NO_3)_3催化涂层的自腐蚀电流密度分别为2.562×10~(-6) A/cm~2和7.821×10~(-7) A/cm~2,其耐蚀性提升明显;HCl和Ce(NO_3)_3催化涂层阻抗极化电阻值由镁合金基材的224.9Ω分别增大至4 401Ω和53 888Ω,HCl催化涂层的失效时间为1 d,Ce(NO_3)_3催化涂层失效时间延长为3 d。可见,两种催化剂制备的涂层,Ce(NO_3)_3催化涂层防护更持久,耐蚀性更好。     

Effect of some ternary additions on the sulfidation of Ni-Mo alloys

Five ternary additions, Cr, Ti, Mn, V, and Al were studied at equi-atomicpercent levels (17 a/o) for their effect on the sulfidation behavior of Ni-19a/o Mo (28–30 w/o) over the range of 600–800°C in 0.01 atm S₂. Al was by far the most effective addition. A linear decrease in log k_p vs. Al content was observed up to 7.5w/o Al, beyond which no further change was observed. All alloys followed the parabolic rate law. Arrhenius plots gave activation energies of 36.9–41.2 Kcal/mol for alloys containing Ti, Cr, Mn, and V, whereas the activation energies for Al-containing alloys were 47.2 Kcal/mol, indicating that a different diffusion process was involved. Complex scales were formed on all alloys, consisting of an outer layer of Nis_1+x and complex inner layers which depended upon alloy composition. Two alloys, those with Cr and Mn, formed intermediate layers of Cr₂S₃ and MnS, respectively, but these layers had little effect on the kinetics. MoS₂ was a constituent of the inner scales except for the alloys with Al. A ternary sulfide, Al_0.55Mo₂S₄ and Al₂S₃ were observed. The presence of the mixed sulfide was always associated with the low sulfidation rates. The formation of MoS₂ on alloys results in a different, less-protective behavior than for MoS₂ formed on pure Mo. This effect is due to the intercalation of Ni into MoS₂ in octahedral positions between the weakly bonded layers of covalently bonded sheets of trigonal prisms. The size of Al⁺³ is too small to be intercalated, and thus MoS₂ is destabilized by Al.     

Effect of Y2O3 additions on the plasticity of sintered Cr2O3

We have carried our constant strain-rate compression tests on polycrystalline Cr₂O₃ and Cr₂O₃ doped with 0.09 wt. % Y₂O₃ to establish whether there exists an effect of Y₂O₃ on the plasticity of Cr₂O₃. This study is motivated by previous work on the oxidation of alloys containing reactive-element additions. In that work, it has been observed that the addition of oxygen-active elements, such as Y to alloys that form Cr₂O₃ or Al₂O₃ oxide layers upon exposure at high temperature, strongly enhances the adhesion of the oxide layer to the base alloy as compared with alloys without reactive-element additions. We have found that at 1200°C (1) chromia exhibits limited plasticity at high temperatures, and (2) the presence of Y in the oxides does not enhance plasticity compared with addition-free oxides.     

The combined effect of refractory coatings containing reactive elements on high temperature oxidation behavior of chromia-forming alloys

The high temperature oxidation behaviors of chromia-forming alloys (F17Ti and Fe-30Cr alloys) have been studied at 1273 K under isothermal conditions and at 1223 K under cyclic conditions, in air under the atmospheric pressure. To extend the oxidation lifetime, coatings have been applied onto the alloy surfaces. Al₂O₃ and Cr₂O₃ films doped with Sm₂O₃ or Nd₂O₃ were prepared via the metal-organic chemical vapor deposition technique. Single Cr₂O₃, Al₂O₃, Nd₂O₃ and codeposited Cr₂O₃-Nd₂O₃, Al₂O₃-Nd₂O₃, Al₂O₃-Sm₂O₃ coatings drastically improved the chromia-forming alloy high temperature oxidation behavior, since they decreased the oxidation rate and enhanced the oxide scale adhesion. Results showed that a critical amount of reactive element (Nd or Sm) in chromia or alumina coatings (11-18 at.%) was needed to observe the most effective effect. The fast precipitation of NdCrO₃ or NdTi₂₁O₃₈ and the segregation of reactive elements at the chromia grain boundaries slowing down outward cation transport and consequently blocking the chromia grain growth, was supposed to be the main reasons of the beneficial effect ascribed to the reactive elements in chromia scales.     

Effect of Nb on the high-temperature sulfidation behavior of cobalt

The sulfidation behavior of Co-Nb alloys containing up to 30wt.% Nb was studied in sulfur vapor at a pressure of 0.01 atm in the temperature range of 600–700°C. Increasing niobium content decreased the sulfidation rate, following the parabolic rate law. An activation energy of 25.6 kcal/mole was obtained for Co-10Nb, Co-20Nb, and Co-25Nb, while a value of 20.5 kcal/mole was found for Co-30Nb. All were two-phase alloys, consisting of solid solution -Co and the intermetallic compound, NbCo₃. The two-phase alloys formed a rather thick outer layer of cobalt sulfides and a heterophasic inner layer that was complex. The inner layer always contained the mixed sulfide CoNb₂S₄ which, depending on the alloy composition, coexisted with cobalt sulfide, NbS₂, and / or NbCo₃ particles. Short-time sulfidations showed that the solid solution initially sulfidized rapidly to form nodules of cobalt sulfide, whereas the NbCo₃ phase formed a thin protective layer of NbS₂. The nodules grew laterally until they coalesced into the continuous, outer thick layer, while the NbS₂ completely or partially reacted with the cobalt sulfide to form CoNb₂S₄. Platinum markers were always found at the interface between the inner and outer scales, the location of the original metal surface.     

改进型镁扩散法制备高临界电流密度MgB2超导体性能研究

本文采用一种改进型镁扩散法成功制备出密度达到1.95g/cm₃的MgB₂超导块材。论文研究了不同的热处理条件对MgB₂块材的超导转变温度(T_c)和临界电流密度(J_c)性能的影响。采用最佳热处理条件制备的MgB₂超导体T_c和J_c分别达到了38.1K和0.53MA/cm₂(10K,自场)。为了改进镁扩散法MgB₂超导体中弱的高场磁通钉扎性能,本文还研究了nano-Pr₆O₁₁和C掺杂对MgB₂超导体的临界电流密度和不可逆场(H_irr)的影响。结果表明C掺杂的MgB₂超导体临界电流密度在10K,6T下达到了10₄A/cm₂,该结果比未掺杂MgB₂超导体在同样条件下性能提高了两个量级,甚至比固态反应法制备的nano-C掺杂MgB₂超导体性能更好。利用该方法制备的nano-Pr₆O₁₁掺杂的MgB₂超导体在10K,2T下也比未掺杂样品J_c提高达9.4倍。根据大量的实验结果和理论分析我们提出基于改进型镁扩散法和化学掺杂,包括纳米粒子和C掺杂,很有可能是一种制备高性能MgB₂超导体非常有效的途径。     

Protective effect in sulfuric acid media of alumina and ceria oxide layers electrodeposited on stainless steel

The influence of thin layers of Al₂O₃ and Ce₂O₃-CeO₂, electrodeposited on stainless steel OC4004, on the corrosion behaviour of the systems Al₂O₃/SS, Ce₂O₃-CeO₂/SS and Al₂O₃-Ce₂O₃-CeO₂/SS has been studied in sulfuric acid medium. A pronounced stabilizing effect on the passive state of steel and enhancement of its corrosion resistance has been established both for the samples as deposited and for the thermally treated Ce₂O₃-CeO₂/SS systems. In comparison to them the layers of Al₂O₃ have a substantial impact on the corrosion resistance of the Al₂O₃/SS system only in the cases when the system is not subjected to thermal treatment. The consecutive deposition of Al₂O₃ and Ce₂O₃-CeO₂ films on SS gives as a result an outstanding corrosion-protective effect, whereupon the corrosion potential of the system Al₂O₃/Ce₂O₃-CeO₂/SS is shifted in positive direction with ∼ 0.3 V for the samples as deposited and with ∼ 1 V—for the thermally treated samples. The so established favourable effect has been explained by the increased concentration of chromium oxides in the surface passive film, caused by the presence of cerium oxides, as well as by their action as cathode, effective with respect to the reduction corrosion reaction, shifting strongly the potential (at which this reaction is occurring) in positive direction.