NiCr涂层结构对Nb-1Zr合金抗氧化性能的影响

为提高Nb-1Zr合金基体在600℃大气环境下的抗氧化性能,采用等离子增强电弧离子镀技术在Nb-1Zr合金表面低于300℃下实现不同复合结构的NiCr涂层。利用恒温氧化表征了涂层在600℃、500 h大气环境下的抗氧化性能,揭示了不同复合结构涂层失效以及抗氧化机理。结果表明,单一NiCr涂层中存在的大量"微孔"结构缺陷相互连通构成了氧元素进入基体的扩散通道,界面处基体首先发生氧化,生成以Nb_2O_5为主的粉末状氧化产物。随着氧化时间的延长,氧化产物逐渐增多,体积逐渐膨胀,造成表面鼓泡直至破裂失效。采用NiCr多层复合结构能够显著降低涂层中形成"贯穿孔"的几率,但并未改变涂层的失效方式。而基体与NiCr层之间引入Cr过渡层,能够在界面处与扩散进入的氧首先反应生成致密的Cr_2O_3层,阻碍氧向基体的进一步扩散,且随着氧化时间的延长,涂层中的Cr向表面的扩散使得其表面相应形成一层致密的Cr_2O_3层,双层致密氧化膜的形成确保了基体抗氧化性能的提高。结果显示,Cr/NiCr多层复合结构涂层能够使Nb-1Zr合金在600℃大气环境下的抗氧化时间延长至500 h,氧化增重率仅有0.08g·(m~2·h)~(-1)。     

电弧离子镀制备耐事故包壳材料厚Cr涂层及高温抗氧化性能

目的在Zr-4包壳材料表面制备具有耐事故高温性能的抗氧化厚Cr涂层,保护Zr基体,以防止与高温水蒸汽反应。方法采用自主研发的φ155 mm大弧源电弧离子镀技术在Zr-4合金表面制备约20μm的Cr涂层,通过X射线衍射仪(XRD)分析氧化前后的物相变化,通过扫描电子显微镜(SEM)和电子探针(EPMA)研究厚Cr涂层在不同温度下产生的多种缺陷,探究厚Cr涂层对Zr基体的防护机制。结果当涂层沉积速率3μm/h,制备的Cr涂层均匀致密,结合力优异,具有柱状晶结构,可经受至少15.8%的形变量,其抗塑性形变能力优异。沉积Cr层样品经过1000、1100、1200℃氧化,保温1h后快速冷却至室温,厚Cr涂层分化为Cr Ox层、Cr_2O_3层、残余Cr层和Cr-Zr扩散层。经受苛刻条件(1200℃/3600 s)测试,除保持连续性的氧化层外,在基体上仍残余良好结合的6.8μm Cr层。氧化层两次开裂阻止基体被进一步破坏。Cr-Zr扩散层是由Zr元素向Cr涂层方向渗透生长的。1200℃时,在基体近表面处产生的大尺寸隆起,是由于在近表面处韧性β-Zr(O)相转变为脆性α-Zr相,以及Cr偏聚贫Sn造成的。残余Cr层的柱状晶结构会形成Zr-O扩散通道,对涂层最后失效将起关键作用。结论 Zr合金包壳材料镀覆20μm的Cr涂层具有充分的耐事故能力,在严苛的事故条件测试下,各缺陷均未能使Zr-4合金基体暴露,涂层能够形成有效壁垒,防止锆合金基体暴露造成核事故,阻止基体进一步被破坏。     

锆合金表面Mo/Al/Cr复合涂层的抗高温水蒸气氧化性能

锆合金是重要的核燃料包壳材料,在包壳表面沉积抗高温水蒸气氧化涂层是在失水事故中避免核泄漏的有效途径,然而涂层在高温氧化过程中存在氧化产物不稳定及界面扩散问题。用磁控溅射的方法在Zr-4合金表面沉积Mo/Al/Cr复合涂层,拟利用Al层生成氧化铝提升抗氧化温度上限,利用Mo层阻挡Al与Zr-4基体的扩散。用SEM表征涂层的表面及横截面形貌,利用XRD分析涂层物相结构,用纳米压痕的方法评价涂层的力学性能,用管式炉连接水蒸气发生器来评价涂层的抗高温水蒸气氧化性能。结果表明：在锆合金表面制备的Mo/Al/Cr复合涂层与基体结合良好,结构完整,界面清晰,硬度高于Zr-4合金基体。在高温水蒸气氧化试验中,复合涂层中的Al会发生熔融,导致涂层结构的破坏而不能生成连续致密氧化铝膜。在Cr层、Al层失效的情况下,Mo层可以有效阻挡Al及O元素向基体内部扩散。探讨了Al作为抗氧化层及Mo作为扩散阻挡层的可行性,试验结果可为核燃料包壳涂层的设计选材提供借鉴和支撑。     

磁控溅射沉积CrAlN涂层抗高温氧化性能研究

采用非平衡磁控溅射技术在M2工具钢表面沉积Cr Al N涂层,利用SEM、EDS、XRD、纳米压痕仪研究了Cr Al N涂层不同温度氧化后的表面和截面形貌、成分、相结构、硬度和弹性模量。结果表明,Cr Al N涂层在高温环境下氧化生成的Al_2O_3和Cr_2O_3致密氧化层可以有效阻止氧进一步向内扩散,涂层在900℃氧化2 h后的氧化层深度仅0.2μm。Cr Al N涂层900℃氧化后仍基本保持氧化前的力学性能。     

Cr涂层锆合金包壳高温蒸汽氧化动力学及微观机理研究

Cr涂层锆合金包壳具备抗高温蒸汽氧化性能优异、耐腐蚀和耐磨蚀性能良好、工程应用难度较小等特点,成为最具前景的近期型事故容错燃料候选材料之一。本工作以Zr-1Nb合金管为基体材料,采用磁控溅射工艺制备均匀致密Cr涂层,涂层厚度范围12～15μm。通过同步综合热分析仪开展双面高温蒸汽氧化试验,氧化温度为1000、1100和1200℃,氧化时间为300～5000s,系统研究反应堆事故工况下Cr涂层锆合金包壳高温蒸汽氧化行为。采用扫描电子显微镜、能谱仪和X射线衍射仪表征高温氧化产物膜微观形貌特征、氧化层厚度、元素分布以及物相组成等,建立Cr涂层氧化动力学模型,探讨高温氧化机理。研究表明,高温蒸汽环境中,Cr涂层锆合金包壳外壁形成致密Cr2O3层,有效阻止O元素扩散至Zr合金基体,从而提升复合包壳的耐高温性能。其次,Cr涂层高温蒸汽氧化动力学曲线遵循抛物线规律,氧化速率常数比锆合金低大约2个数量级,显著提升锆合金包壳抗高温蒸汽氧化性能。     

微晶化对Ni20Cr合金热生长氧化膜应力的影响

利用氧化膜应力原位测量装置对Ni20Cr微晶涂层/合金体系在1000℃空气中氧化过程中发生的弯曲挠度变化进行测量.结果表明,微晶涂层1000℃氧化所形成的Cr_2O_3氧化膜中存在压应力,应力绝对值高于相同厚度的合金表面的热生长氧化膜,其原因在于涂层/Cr_2O_3界面结合好,应力释放较小.降温冷却过程中,通过微晶涂层...     

Cr_3C_2-NiCr涂层的高温抗氧化和耐热腐蚀性能

采用大气等离子喷涂技术制备Cr_3C_2-NiCr复合涂层,并对制备的Cr_3C_2-Ni Cr涂层试样进行800℃×100 h氧化和熔盐(Na_2SO_4+25wt%NaCl)热腐蚀试验。利用X射线衍射仪(XRD)和带能谱的扫描电镜(SEM/EDX)分析氧化、腐蚀涂层表面和截面的成分及结构变化,探讨其高温氧化、腐蚀机理。结果表明:等离子喷涂Cr_3C_2-Ni Cr涂层具有层状组织结构,喷涂过程中无明显相分解或氧化。高温氧化后的Cr_3C_2-NiCr涂层表面及层片界面形成了连续、致密的Cr_2O_3保护膜,涂层表现出优异的抗高温氧化性能。在热腐蚀过程中,腐蚀盐破坏了涂层表面及层片界面形成的氧化膜,腐蚀性元素沿着涂层中的孔洞及层片界面扩散到涂层内部,涂层发生"活化氧化",耐腐蚀性较差。     

热处理对S30432喷丸不锈钢抗高温水蒸汽氧化性能的影响

将S30432钢喷丸样品进行不同温度热处理,研究样品620℃下在90%H_2O+10%Ar气氛中的氧化行为。采用光学显微镜(OM)观察喷丸形变层组织形貌;通过测量不同时间氧化膜厚度,获得氧化动力学曲线;利用X射线衍射仪(XRD)、扫描电镜(SEM)及能谱仪(EDS)等对氧化产物成分、形貌及结构进行分析。结果表明:热处理过程中S30432钢喷丸样品形变层组织形貌无明显变化;氧化过程中,样品喷丸形变层内晶粒发生再结晶长大;氧化2000 h后,样品喷丸形变层内晶粒尺寸及碎化晶层厚度基本相同。不同温度热处理的S30432钢喷丸样品在高温水蒸汽中均生成由Cr_2O_3、(Fe,Cr)_2O_3、FeCr_2O_4以及少量Fe_3O_4和Fe_2O_3组成的富Cr氧化物薄膜。730～800℃热处理对S30432喷丸不锈钢抗高温水蒸汽氧化性能无明显影响。     

超音速火焰喷涂制备Cr涂层及其高温氧化性能

目的 探索一种高效制备核电用包壳材料锆合金表面涂层的方法,以应对反应堆失水事故,提高核电安全性。方法 采用超音速火焰喷涂技术在Zr-4合金表面制备Cr涂层,高温氧化试验在1 200 ℃空气中进行,氧化时间30 min。通过X射线衍射仪(XRD)、扫描电镜(SEM)研究Cr涂层氧化前后的结构和显微组织。采用划痕法测试涂层与基体结合力。采用金相显微镜(OM)观察划痕形貌。结果 采用HVOF技术可以在锆合金基体上制备的涂层主要为体心立方结构的金属Cr同时含有约21.9%密排六方结构(HCP)的Cr2O3。抛光可以减少Cr2O3至约10.1%。涂层由层状结构、未熔颗粒和少量孔隙组成。Cr2O3主要分布在层状结构中,未熔颗粒形成的不规则块状结构基本不含氧,主要为金属Cr。涂层与基体的结合力为77~94 N。喷涂工艺参数为煤油流量23 L/h、氧气流量880 L/h、喷涂距离330 mm的涂层样品结合力最高,为94 N。在1 200 ℃空气中氧化30 min后,涂层靠近基体界面处形成11~14 μm厚的连续致密层,而靠近界面处的基体衬度变暗,能谱信息显示含有Cr,因此判断该区域为Zr-Cr过渡层,厚度约为5 μm,说明存在基体与涂层的互扩散层,且Zr向涂层的扩散速率明显大于Cr向基体的扩散速度。有Cr涂层的Zr基体没有发生氧化,涂层内部也基本没有氧化,而没有涂层覆盖的基体氧化层厚度在120 μm以上。结论 采用HVOF可以在锆合金表面制备出结构致密、与基体结合紧密且抗高温氧化性能优良的金属Cr涂层。     

Al-Si涂层改性TP347H FG在650℃饱和蒸汽下的氧化行为研究

利用料浆渗铝法在奥氏体钢TP347H FG上制备了Al-Si涂层,结合氧化增重法、扫描电镜观察及XRD分析,研究了TP347H FG以及Al-Si涂层的饱和蒸汽氧化行为,并以高Cr含量的HR3C合金为参比对象。结果表明,TP347H FG基体抗氧化能力不足,外层疏松层瘤状氧化物Fe_3O_4与表面氧化膜下方内氧化物FeCr_2O_4呈双层结构,650℃氧化600 h后外层氧化膜发生严重剥落;制备Al-Si涂层后,试样表面形成保护性Al_2O_3氧化膜,可显著提升TP347H FG钢抗蒸汽氧化能力,并与HR3C相当;HR3C合金中较高的Cr含量促使HR3C在较短时间内,表面即形成致密连续的Cr_2O_3膜,氧化动力学遵循抛物线规律。     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

Rheology Feature of Simple Metal Melt

The rheology feature of Sb, Bi melt and alloys was studied using coaxial cylinder high-temperature viscometer. The results showed that the curve of torsion-rotational speed for Sb melt presents a linear relation in all measured temperature ranges, whereas for the Bi melt, the curve presents obvious non-Newtonian feature within the low temperature range and at relative high shear stress. The rheology feature of Sb80Bi20 and Sb20Bi80 alloy melts was well correlated with that of Sb and Bi, respectively. It is considered that the rheology behavior of Sb melt plays a crucial role in Sb80Bi20 alloy and that of Bi melt plays a crucial role in Sb20Bi80 alloy.     

Microstructures and Mechanical Properties of a Newly Developed Austenitic Heat Resistant Steel

The effect of heat treatment on the microstructures and mechanical properties of a newly developed austenitic heat resistant steel(named as T8 alloy) for ultra-supercritical applications have been studied. Results show that the main phases in the alloy after solution treatment are γ and primary MX. Subsequent aging treatment causes the precipitation of M_(23)C_6 carbides along the grain boundaries and a small number of nanoscale MX inside the grains. In addition, with increasing the aging temperature and time, the morphology of M_(23)C_6 carbides changes from semi-continuous chain to continuous network.Compared with a commercial HR3C alloy, T8 alloy has comparable tensile strength, but higher stress rupture strength. The dominant cracking mechanism of the alloy during tensile test at room temperature is transgranular, while at high temperature, intergranular cracking becomes the main cracking mode, which may be caused by the precipitation of continuous M_(23)C_6 carbides along the grain boundaries. Typical intergranular cracking is the dominant cracking mode of the alloy at all stress rupture tests.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

The 15th Global Foundry Sourcing Conference 2014held in Qingdao China

Organized by Suppliers China Co., Ltd and co-organized by the National Technical Committee 54 on Foundry of Standardization Administration of China, the 15th Global Foundry Sourcing Conference 2014 （hereinafter referred to as FSC 2014） was successfully held on Sep. 23rd in Grand Regency Hotel, Qingdao. More than 500 delegates from home and abroad attended this conference, including over 130 purchasers from 20 countries and 380 domestic and foreign suppliers.     

Secondary Recrystallization Behaviors of Grain-Oriented 6.5 wt% Silicon Steel Sheets Produced by Rolling and Nitriding Processes

By rolling and nitriding processes, 0.23- to 0.3-mm-thick grain-oriented 6.5 wt% silicon steel sheets were produced. The core losses of grain-oriented 6.5 wt% silicon steel at frequencies ranging from 400 Hz to 20 k Hz were lower than that of the grain-oriented 3 wt% silicon steel with the same thickness by 16.6–35.8%. The secondary recrystallization behavior was investigated by scanning electron microscopy, energy-dispersive spectroscopy, and electron backscattered diffraction. The results show that the secondary recrystallization in high-silicon steel sheets develops more completely as the nitrogen content increases after nitriding, secondary recrystallized grain sizes become larger, and the sharpness of Goss texture increases. Because more {110}116 grains in the subsurface and the central layer of the sheets have a lot of 20°–45° high-energy boundaries in addition to Goss grains, {110}116 can be the main component through selective growth during secondary recrystallization when the inhibitor quantity is not enough and inhibitor intensity is weaker. The increases in nitrogen content can increase the inhibitor intensity and hinder abnormal growth of a mount of {110}116 grains and therefore enhance the sharpness of Goss texture.     

Laser Cladded TiCN Coatings on the Surface of Titanium

Laser cladded coatings of TiCN were produced on the surface of titanium. To obtain the optimal techniques, several conditions were tested by varying the laser scanning rate. The choice of shielding gas was also studied. The cladded coatings were then evaluated from the surface mechanics point of view based on their microhardness. The microstructure of some interesting samples was investigated by optical micrographs (OM). The results showed that under the condition of fixed pulse frequency and pulse width, the laser scanning rate and the shielding gas are the main factors influencing the components of coatings. TiCN coatings were decompounded and oxidized during the cladding process in the condition of no shielding gas of N2. X-ray diffraction results indicated that the composite coatings composed of TiCN, TiC, Ti2N, and TiO2 were produced using appropriate techniques. The results indicated that the best condition in terms of the surface microhardness is obtained when the scanning rate is 1.5mm / s, the pulse frequency is 15Hz, the pulse width is 3.0ms, and N2 is chosen as the shielding gas. The microhardness of the composite coatings is about 1331kg · mm - 2, which is about 4 times that of the substrate. The optical micrographs indicated that the cladding zone is made up of TiCN, TiO2, and some interdendritic Ti, but the diffusion zone mainly consists of the dendrites phase, and the cladded depth is about 80?滋m, which is more than 2 times that of the laser nitrided sample. There were no microcracks or air bubbles in the cladded sample, which was cladded using the above optimal techniques.     

Effect of Short-Time Aging on the Pitting Corrosion Behavior of a Novel Lean Duplex Stainless Steel 2002

The effect of short-time aging in the temperature range between 400 and 1000 °C on the pitting corrosion behavior and mechanical property of a novel lean duplex stainless steel(LDSS) 2002 was investigated through the potentiostatic critical pitting temperature(CPT) tests and the Charpy impact tests. Both the pitting corrosion resistance and the toughness of aged specimens degraded due to the precipitation of detrimental secondary phases and the most significant reduction of CPT and impact energy emerged at 650 °C concurrently. The CPT of LDSS 2002 specimen aged at 650 °C decreased by 28 °C, and the impact energy dropped from 69 to 29 J/cm~2 compared with the solution-annealed sample. Transmission electron microscopy characterization showed that the main precipitates in LDSS 2002 were Cr_2N and M_(23)C_6 along the ferrite–austenite grain boundaries.     

Information for Contributors

正The Transactions of Nonferrous Metals Society of China,founded in 1991 and sponsored by The Nonferrous Metals Society of China,is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology,including mineral processing,extraction metallurgy,metallic materials and heat treatments,metal working,physical metallurgy,powder metallurgy,with the emphasis