铬基钨镍钼高耐磨合金耐磨机理及产业化

本文研究了铬基钨镍钼高耐磨合金的耐磨机理。重点分析了铬基钨镍钼高耐磨合金的铸造工艺流程、铸造用废砂回收再生树脂砂的利用技术以及基于铬基钨镍钼高耐磨合金的耐磨产品。结果表明:铬基钨镍钼高耐磨合金的各种成分在不同工况中具有良好的耐磨性能。     

Electrodeposition preparation of Nafion-Pt-HxMoO3 and its activity toward methanol oxidation

A composite catalyst Nafion-Pt-HxMoO3 was prepared on a glassy carbon by cyclic voltammetry methods in sulfuric acid solution containing Na2MoO4, H2PtCl6 and Naton, and its activity for the methanol oxidation was studied with Pt-HxMoO3 as comparison. It is found that the electrocatalytic activity and the stability of Pt-HxMoO3 are improved by the Nation. The activity of Pt-HxMoO3 reaches its maximum when the content of Nation in the preparation solution is 0.012%（mass fraction）. In this case the oxidation peak current of methanol on Nation-Pt-HxMoO3 is 1.76 times larger than that on Pt-HxMoO3 and keeps unchanged when the potential is set at 0.3 V （vs Hg-Hg2SO4） for 5 000 s in 1 mol/LCH3OH＋0.5 mol/L U2SO4 solution. The results from energy dispersive spectroscopy show that the content of Nation in the composite is 0.57%. The results from scanning electron spectroscopy show that the composite of Nafion-Pt-HxMoO has a gain size of about 90 nm and distributes more uniformly than Pt-HxMoO3.     

钼精矿供应紧张支撑钼市场

介绍了2006年上半年国际、国内钼市场的产量、供需平衡及进出口情况。西方世界钼产量平稳，钼价格呈现出上涨趋势。西方世界钼铁平均价格1月份为53．5～55．8美元／kg，6月份为58．71～60．07美元/kg，上涨9．72％；中国产钼铁在鹿特丹仓库现货价格1月份为50．99～53．70美元／kg，6月份为58．51～60．03美元／kg，上涨14．74％。分析了上半年国际、国内钼市场的形势，预测下半年国际钼市场钼精矿供应仍将紧张，副产钼供应平缓，因此下半年的钼市场将得到支撑。     

利用双层辉光放电形成Mo-N硬质镀层

用双层辉光放电在钛合金Ti6Al4V表面形成了Mo-N硬质镀层。用X射线衍射仪和纳米压入仪分别对镀层的相结构、硬度和弹性模量进行了研究，并用涂层压入仪对镀层与基体间的结合强度进行了测定。结果表明：Ti6Al4V表面形成了均匀的Mo—N硬质镀层，镀层厚约10μm，由面心立方结构Mo2N化合物构成；Mo2N硬质镀层的硬度和弹性模量分别为13．80GPa和261．65GPa;镀层与基体间具有较好的结合强度。     

Influence of nickel and molybdenum on the phase stability and mechanical properties of maraging steels

The effect of nickel and molybdenum concentrations on the phase transformation and mechanical properties of conventional 18Ni(350) maraging steel has been investigated. Both of these elements act as strong austenite stabilizers. When the concentration of molybdenum or nickel is greater than 7.5 or 24 wt %, respectively, the austenite phase remains stable up to room temperature. In both molybdenum- and nickel-alloyed steels, the austenite phase could be transformed to martensite by either dipping the material in liquid nitrogen or subjecting it to cold working. When 7.5 wt% Mo and 24 wt% Ni were added in combination, however, the austenite phase obtained at room temperature did not transform to martensite when liquid-nitrogen quenched or even when cold rolled to greater than 95% reduction. The aging response of these materials has also been investigated using optical, scanning electron, and scanning transmission electron microscopy.     

Induction plasma spheroidization of tungsten and molybdenum powders

The melting, evaporation and oxidation behaviors as well as the solidification phenomena of tungsten and molybdenum in induction plasma were studied. Scanning electron microscopy was used to examine the morphology and the cross section of plasma-processed powders. X-ray diffraction was used to analyze the oxides formed on the particle surface of these two metals. The influence of spray chamber pressure on the spheroidization and oxidation phenomena was discussed. The results show that fewer Mo particles than W particles are spheroidized at the same powder feed rate under the same plasma spray condition although molybdenum has a lower melting point. A small fraction of tungsten is evaporized and condensed either on the surface of tungsten particles nearby or on the wall of spray chamber. Tungsten oxides were found in tungsten powder processed under soft vacuum condition. Extremely large grains form inside some spheroidized particles of tungsten powder.     

Dry friction and wear characteristics of MoSi2 against ahoy steels

The dry friction and wear characteristics of three kinds of friction couples under different loads, MoSi2/45 tempered steel, MoSi2/45 quenched steel, and MoSi2/CrWMn steel, were investigated by using a friction and wear tester. SEM and X-ray diffraction were employed to analyze the microphotograph of the worn surface and the phase of worn pieces in order to reveal the wear mechanisms of MoSi2 material. The results show that MoSi2/CrWMn steel friction pair has good dry friction and wear properties under the load of 80 N, where the friction coefficient is 0.255 and the wear rate of MoSi2 is only 14.72 mg.km-1. But under the load of 150 N, it is MoSi2/45 tempered steel friction pair that has good tribological properties,MoSi2 under low loads is brittle fracture. With the increase of load, the main wear mechanism of MoSi2 against 45 quenched steel or CrWMn steel is adhesive wear. However, the wear mechanism of MoSi2 against 45 tempered steel is changed from oxidation-fatigue wear to adhesive wear.     

Y2O3／CeO2复合强化钼合金（MYC）丝的研究

采用粉冶法制备了添加Y2O3／CeO2(≤0．6w％)的复合强化钼合金(MYC)丝。用XRD标定合金相组成，用SEM观察合金的显微组织，用万能电子拉伸机测定合金丝的力学性能并将测定结果与纯钼丝进行了对比研究。研究结果表明：添加Y2O3／CeO2复合强化钼合金的相组成为Mo，YMoO4和CeO2；MYC合金断口具有典型的塑性断裂特征，MYC合金丝在1600℃退火后仍然表现明显的纤维状织构组织形态。     

Molybdenum and tungsten coatings for x- ray targets obtained through the low-pressure plasma spraying process

Low-pressure plasma spraying under an argon atmosphere was employed to deposit molybdenum and tungsten coatings on different metallic, ceramic, and composite substrates. Molybdenum coatings ob-tained through this technique presented a homogeneous structure with an average porosity of about 17 %. These coatings exhibited adhesion greater than 40 MPa on molybdenum and grey cast iron (FT25) substrates. No adhesion was observed on an A1N surface regardless of the preheating temperature and/or surface preparation. Adhesion on AIN-Mo (AM25) composite substrate, containing 25 % dispersed metal-lic phase by volume, showed intermediate results. Tungsten coatings exhibited porosity between 10 to 12% and a typical lamellar structure. The adhesion of tungsten coatings on molybdenum and FT25 sub-strates was around 40 MPa.     

间接法选择性激光烧结技术制备高温特殊复合材料

系统地介绍了覆膜钼粉的制备、烧结成型及后处理工艺技术,总结了间接法选择性激光烧结技术的优缺点,并对该技术进行了展望。