Mechanism of Action of Rare Earths in High Effective Fe Powder Welding Rods

The optimum coating composition of alkali Fe powder welding rods was designed by orthogonal experiment with mix rates. A new kind of effective RE-Fe powder welding rod was prepared which could be used at the condition of direct and indirect current. The arc characteristics and stabilities of effective Fe powder welding rods containing RE were analyzed by HANNOVER analyzer. The efficiency of Fe powder welding rods was tested by weighting method. It was found that the stability of Fe powder welding rods was improved when it was added with rare earths. The results of impact experiment at low temperatures and SEM analysis on impact break showed that the grain was refined, the welding joint was cleaned, and the mechanical properties of joint was enhanced with proper RE content. It was provided with good processing property for this effective RE-Fe powder welding rod, and its efficiency could arrive at 180%.

Recovery of waste rare earth fluorescent powders by two steps acid leaching

The effects of the acid leaching and alkali fusion on the leaching efficiency of Y,Eu,Ce,and Tb from the waste rare earth fluorescent powders were investigated in this paper.The results show that hydrochloric acid is better than sulfuric acid in the first acid leaching,and NaOH is better than Na2CO3in the alkali fusion.In the first acid leaching,the Wloss is 20.94%when the waste rare earth fluorescent powders are acid leached in H?concentration 3 mol L-1and S/L ratio 1:3 for 4 h due to red powders dissolved.The better results of the alkali fusion can be got at 800℃ for 2 h when the NaOH is used.The blue powders and the green powders can be dissolved into NaAlO2and oxides such as rare earth oxide(REO).The REO can be dissolved in H?concentration 5 mol L-1,S/L1:10 for 3 h in the second acid leaching.The leaching rates of the Y,Eu,Ce,and Tb are 99.06%,97.38%,98.22%,and 98.15%,respectively.The leaching rate of the total rare earth is 98.60%.

Improvement of Ductility of Powder Metallurgy Titanium Alloys by Addition of Rare Earth Element

Ti-4.5Al-6.0Mo-1.5Fe, Ti-6Al-1Mo-1Fe and Ti-6Al-4V alloys were prepared by blended elemental powder metallurgy （PM） process, and the effects of Nd on the microstructures and mechanical properties were investigated by scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and X-ray diffraction （XRD）. It was found out that the addition of Nd increased the density of sintered titanium alloys slightly by a maximum increment of 1% because small amount of liquid phase occurred during sintering. The addition of Nd shows little effect on the improvement of tensile strength, while the elongation is significantly improved. For example, the elongation of Ti-4.SAl-6.0Mo-1.5Fe can be increased from 1% without addition of Nd to 13% at a Nd content of 1.2 wt pct.

Effect of Rare Earth Elements on Powder Boro-Carbo-Nitriding at Low Temperature

The process of the co-cementation layers of low temperature powder multicomponent thermochemical treatment with B-C-N-RE and the structure and properties were studied and compared with those of conventional boro-carbo-nitriding (B-C-N) by X-ray diffractometer, potentiostat and wear machine. The results show that rare earth elements have significant catalytic effect within proper limits. Both wear resistance and corrosion resistance of the B-C-N-RE co-cementation layer are greatly increased in comparison with those of the B-C-N. The function mechanism of rare earth elements is also discussed.

Preparation of rare-earth-modified medical stone powders and their application as conductive fillers

Traditional metal conductive fillers are expensive and prone to oxidation. Thus, the development of new conductive powders as fillers is urgently needed. A novel gaseous penetration technology was adopted to prepare La-doped medical stone powders(La-MSPs), which are inexpensive mesoporous materials, as a new kind of conductive filler material. The prepared La-MSPs attained a resistivity of 450 ?·m and were used as a filler to prepare conductive coatings with epoxy resin as the resin matrix. The influence of the La-MSPs dosage on the resistance and hardness of the coatings was also determined. The resistance and the hardness both decreased with increasing filler dosage. Finally, the optimum recipe of the conductive coatings with the most suitable fillers dosage(55 wt%) was obtained. The hardness and resistance of the coatings with 55 wt% La-MSPs were HV 4 and 5.5 × 10~7 ?, respectively.

Comparison of Properties of Bastnasite and Fluorocarbonate Rare-earth Polishing Powders

By means of DTA TG, XRD, SEM etc ., the particles configuration, crystal structure, chemical composition and other physical properties of bastnasite rare earth polishing powder and fluorocarbonate rare earth polishing powder were comparatively analyzed. The mechanism of the performance differences between two kinds of polishing powders was also investigated.

Effects of Rare Earth Doping on the Properties of γ-Fe_2O_3 Magnetic Powder

The effects of rare earth doping on the formation process of α-FeOOH crystallite and the properties of γ-Fe2O3 magnetic powder were investigated. The growth of needle α FeOOH crystallite was completed by the basic process. The experimental results show that the rare earth doping can increase the aspect axial ratio of needle α-FeOOH grains. its anti-sintering capability during the heat-treatment and the thermostability of γ-Fe2O3 magnetic properties. The magnetic properties of γ-Fe2O3 doping with rare earth are as follows: the coercivity Hc=36.3 kA/m (445 Oe), the ratio saturation magnetization σs=90.4μWbm/kg (72 emu/g), the ratio remanent magnetization σr=54 μWbm/kg (43 emu/g), and the temperature coefficient of remanent magnetization of γ-Fe2O3 doping with 0.1 mol% Dy can reach -5 ×10-4℃-1.

PREPARING NANO-CRYSTALLINE La DOPED WC/Co POWDER BY HIGH ENERGY BALL MILLING

The La doped WC/Co powder was prepared by high energy ball milling. The changes of crystal structure, micrograph and defect of the powder were investigated by means of XRD (X-ray diffraction), SEM (scanning electron microscope) and DTA (differential thermal analysis). The results show that adding trace La element into carbides is effective to minish the grain size of WC/Co powder. The La doped carbides powder with grain size of 30nm can be obtained after 10h ball milling. The XRD peak of Co phase disappeared after 20h ball milling, which indicated solid solution (or secondary solid solution) of Co phase in WC phase. The La doped powder with grain size of 10nm is obtained after 30h ball milling. A peak of heat release at the temperature of 470℃ was emerged in DTA curve within the range of heating temperature, which showed that the crystal structure relaxation of the powder appeared in the process of high energy ball milling. After consolidated the La doped WC/Co alloy by high energy ball milling exhibits ultra-fine grain sizes and better mechanical properties.

Effect of Roasting Conditions of Rich Cerium Rare Earth Carbonate on Crystallite Morphology and Polishing Ability of Ceria-Based Rare Earth Oxide

The granule shape and crystal structure of the the ceria-based rare earth oxide which were roasted at 600～1050 ℃ for 2～6 h and then cooled in furnace, cooled out of furnace or cooled in water were studied by means of XRD and SEM. The results revealed that the rich cerium rare earth carbonate could be changed into the rare earth oxide which was a kind of sandwich made of globose granule whose diameter was between 0.5～3.0 μm after being roasted in 900 ℃ for 2 h. This kind of crystal lattice in rare earth oxide belonged to face-centered cubic lattice and its space between crystal surface {111} and {200} (viz. L111 and L200) would enlarge as the roasting temperature increasing. With increasing roasting temperature, L111 would rise straightly upward, and L200 would rise straightly upward when roasting time was 2～4 h but changed little when roasting time was 4～6 h. The glass-polishing experiments found that the polishing ability of the ceria-based rare earth oxide was the best as L111 was 43～53 nm and the L200 was 43～56 nm.

Effect of Rare Earth on Diamond-Tungsten Carbide Super-Hard Composites

A study was undertaken to decrease the sintering temperature and to increase the thermal stability of diamond by adding rare earth elements. The critical factor in the activated sintering is the content of rare earth element. The results show that adding 0.3% rare earth to the powders makes the composites obtain the properties needed.

Effect of Rare Earth on the Crystallization Behavior of Li_2O-Al_2O_3-SiO_2 Glass-ceramic

X-ray powder diffraction and Fourier transform infrared spectroscopy were applied for characterization of Li2O-Al2O3-SiO2 glass-ceramic powders doped with Eu2O3,Gd2O3 and Er2O3,respectively,in the conditions of different heat-treatment temperatures and with various amounts.The powders were derived from the polyacrylamide gel method.The results show that,the wet gels prepared by polyacrylamide perform a unique crystallization behavior in the process of drying,comparing with some customary preparation such as melt processing.The main crystal phase and crystallization sequence of Li2O-Al2O3-SiO2 micro-powders have no distinct with addition of Eu2O3,Gd2O3 or Er2O3,while the crystallization temperature of the β-spodumene decreased and the amount of the β-spodumene increased.

WC-Co硬质合金强化的研究进展

WC-Co硬质合金具有高强度、高韧性、高耐磨性等优点,在工业领域具有广阔的发展前景。对WC-Co硬质合金进行强化,可以进一步提高硬度、耐磨性和断裂韧性等性能,从而拓展其在航空航天、资源开采、装备制造等领域的应用。列举了部分稀土单质和稀土氧化物强化WC-Co硬质合金的研究成果,总结了稀土强化机理,包括细化晶粒、改善黏结相结构、强化晶界,综述了WC-Co硬质合金碳含量控制、烧结、热处理等制备工艺的优化措施,最后对WC-Co硬质合金强化研究中存在的问题进行了总结,并展望了未来的研究方向。

Effects of cubic carbides and La additions on WC grain morphology,hardness and toughness of WC-Co alloys

Effects of Cr3C2,VC and La2O3 additions on the WC grain morphology,hardness and toughness of WC-10Co alloys were investigated.To intensify the grain growth driving force,nano W and nano C,instead of the conventionally used WC,were used as the starting materials.To obtain a three-dimensional WC grain morphology,the natural sinter skins of the alloys were observed directly by scanning electron microscopy.It is shown that the additions have a strong ability in regulating the WC grain morphological and grain size distribution characteristics and the combinations of hardness and toughness.Due to the formation of regular and homogeneous triangular platelet WC grains,WC-10Co-0.6Cr3C2-0.06La2O3 alloy shows an excellent combination of hardness and toughness.The morphological regulation mechanism,the relationship between the WC grain morphology and the properties were discussed.

稀土对激光熔覆WC/Ni-P涂层微磨料磨损性能的影响

利用激光熔覆技术在45钢表面制备了WC/Ni–P复合涂层,在Plint TE–66微磨料磨损试验机上进行了磨损试验,研究了不同稀土含量(CeO2)以及不同粒度WC粉末对涂层熔覆性能、硬度和磨损性能的影响。研究结果表明:稀土的适当加入能够使熔覆时熔体的流动性显著提高,使其气孔率降低,表面平整,能显著提高熔覆层的熔覆性能。随稀土含量增加,涂层组织细化;WC颗粒的加入提高了涂层的显微硬度和耐磨性。在微磨料磨损过程中涂层表面Ni–P基质优先于WC颗粒被磨去,导致WC颗粒从基质中凸起,最后WC颗粒失去基质支撑在磨料的作用下从涂层中脱落。

混合稀土氧化物与再生WC-Co粉制备YG8硬质合金的研究

以混合稀土和再生WC-Co粉混合制备YG8硬质合金为研究对象,对合金性能和组织进行检测。结果表明:混合稀土的加入对合金样品的密度和硬度无影响,对合金的矫顽磁力、钴磁和抗弯强度产生一定的影响,但并不明显。与原生WC粉末制备的硬质合金相比,再生粉末制备的硬质合金,其钴磁和抗弯强度等性能下降严重,而且组织中出现明显的脱碳现象。

纳米稀土对热喷涂WC-12Co涂层的改性作用

利用超音速火焰喷涂技术在45钢基体上制备了不同纳米稀土含量的WC-12Co涂层。通过物相分析并测定材料的显微硬度、结合强度、磨损性能,研究纳米稀土对WC-12Co涂层的改性作用。结果表明:适量纳米稀土的加入使WC-12Co涂层的显微硬度和结合强度显著提高,并且纳米稀土的加入有效地抑制了WC颗粒的脱碳,使组织细化。当纳米稀土含量在1.5wt%时,涂层的耐磨性最好。

含板状晶WC双模组织结构硬质合金的研究

采用超细WC原料 ,在WC 2 0Co合金中加入纳米Y2 O3,在 1 4 4 0℃的液相烧结温度下获得了含板状晶WC双模组织结构的合金。通过对比低于共晶温度下热压固结工艺与传统液相烧结工艺制备的WC 2 0Co 1Y2 O3硬质合金的组织结构发现 ,液相烧结合金中WC板状晶是在液相烧结阶段通过液相重结晶形成的 ,均匀分散在合金中的Y2 O3具有促进WC从粘结相中均匀析出长大、抑制WC沿c轴方向生长的作用 ,因而使合金中粗大的WC呈现板状晶的形貌。研究结果表明 ,板状晶强化的双模结构WC 2 0Co 1Y2 O3合金具有较好的综合性能。

加混合稀土WC-8Co合金的组织和性能

探讨了添加超细混合稀土氧化物微粉对WC－8Co硬质合金组织结构和性能的优化机理．结果表明，混合稀土氧化物提高WC－8CO合金强韧性的原因，不仅是由于WC晶粒尺寸的细化、不连续长大的粗晶WC的消除和立方钻相含量的提高，还与合金制品宏观应力的增加有关。

纳米Ce改性对WC陶瓷涂层微观结构及抗磨损性能的影响

采用超音速火焰热喷涂(HVOF)技术在06Cr13Ni4Mo不锈钢材料表面制备涂层,通过扫描电镜(SEM)、X射线衍射仪、微区X射线荧光光谱仪、结合力试验机、显微硬度计、摩擦磨损试验机、磨蚀试验机、汽蚀试验机等手段研究分析纳米Ce改性对WC陶瓷涂层微观结构及性能的影响。结果表明:稀土元素Ce较为均匀地分布在涂层中,起到细化晶粒、抑制Cr、Co等元素合金化以及提高WC抗氧化性能等效果;涂层的致密性、显微硬度以及结合强度等性能大幅提高;涂层的抗摩擦磨损性能提高1.23倍,抗高泥沙水流的磨损性能提高7.46倍,抗汽蚀性能提高63.6%。

WC-Co硬质合金稀土-硼共渗的高温动态相分析

用高温X射线衍射装置对以B4C为供硼剂、以Y2 O3 为催渗剂的WC 2 0Co硬质合金渗硼表面进行了从室温到 130 0℃连续升温渗硼过程的XRD动态物相分析 ,探讨了稀土 硼共渗机制。结果表明 ,在真空烧结升温期间 ,从WC Co压坯表面B4C分解出来的活性硼原子除在压坯表面上形成硼化物外 ,所形成的高浓度活性硼原子还向压坯内钴中扩散形成三元含硼相W2 Co2 1 B6化合物。同单独渗硼相比 ,钇在稀土 硼共渗过程中有拓宽渗硼温度范围。