Terbium Oxide Price – May 4, 2023

lanthanum oxide image

The overall China’s domestic rare earth market is still weak, mainly reflected in the slight decline in the prices of rare earth products such as praseodymium, neodymium, dysprosium and terbium and the actual transaction volume is small. 

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China Molybdenum Price - May 4, 2023

TZM bar image

China molybdenum price stabilizes in the first trading day after the holiday of Labour Day as most participants do not totally come back from the holiday. At present, the industry is focusing on the shipment situation of molybdenum mining enterprises and the bidding situation of steel enterprises.

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Effect of Coating Preparation Method on Oxidation Behavior of W-Based Materials

Summary of the preparation process and oxidation characteristics of silicide coating on W and its alloy surface image

Researchers summarize the effects of different coating preparation methods on the coating composition and oxidation behavior of W-based materials. It can be seen that the silicide coating consists mainly of a thick WSi2 layer and a thin W5Si3 layer. The HAPC coating requires a longer time due to the relatively low diffusion temperature. After 4~15 hours of treatment at 1100 °C, the thickness of the coating is only 30~60 µm. However, using CVD technology, the thickness of the coating can reach 50~80 microns after 0.5~1 hour of deposition at 1200°C. In contrast, the HDS technique is very efficient for coating preparation. By depositing at 1500°C for 0.25~0.42 h, coatings with thicknesses of 36~88 µm can be obtained.

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Self-Passivating Tungsten Alloys and Surface Coating Protection Technology

Schematic diagram of oxidation failure mechanism of WSi2 coating on W and W-base alloys image

In order to solve the problem of poor oxidation resistance of W and W-based alloys at high temperatures, this work gives self-passivating tungsten alloys and surface coating protection technology. Optimization of the preparation process of the alloy (heat treatment of HIPed alloy, etc.) can effectively reduce or eliminate its internal cracks and holes, thermal stresses and residual stresses, thus reducing its surface roughness and porosity. In addition, some beneficial elements (Ti, Zr, Y, Nb, etc.) can be added to improve the high-temperature strength of W-based alloys, slow down the diffusion of Cr cations, and promote the formation of oxide films.

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Si-WSi2 Coating Prepared by HDS

The mS values vs. exposure time of pure W and W-based alloys oxidized at 1000 temperature for 15 h imageThe mS values vs. exposure time of pure W and W-based alloys oxidized at 1000 temperature for 15 h image

Zhang et al. prepared Si-WSi2 coatings on W substrates by hot-dip silicon-plating (HDS) technique. The HDS method involves placing a solid infiltration source into a corundum crucible under a high-temperature protective atmosphere, heating it until it is completely melted, and maintaining the temperature for a certain period of time. The processed sample is then slowly placed into the crucible and the coating is formed on the surface of the substrate by interpenetration between the substrate and the melt. This method is considered to be a cost-effective coating preparation method, which features short coating preparation time, high deposition temperature, uniform coating composition, smooth surface, and compact structure.

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