Molybdenum News Center

TZM Alloy Manufacturing - Raw Materials Preparation

In TZM alloy manufacturing, to prepare high quality raw materials has great significance for obtaining high-strength sintered alloy blank. Fine powder particles can reduce the sintering temperature, but also easy reunion, is not conducive to mix powder. At the same time, the powder impurities as low as possible, which can improve the density and strength of the alloy, to ensure that composition of the alloy is not out of control. Thus, molybdenum powder particle size is about 2.0 ~ 3.5um and purity is 99.95%, which is most conducive to producing high strength TZM alloy.

Heating TiH₂ and ZrH₂ powder, Ti and Zr will break down form TiH₂ and ZrH₂ and add to Mo powder. Some Ti, Zr will react with matrix to form solid solution strengthening. Another Ti, Zr, will react with O, C to form carbide which is second phase and to produce second phase strengthening. Ti, Zr added by chemical reaction, so the size of Ti and Zr has reached the atomic or molecular level. The minimum fee's size of TiH₂, ZrH₂ can be purchased on the market is smaller than 10um and purity is about 96%.

During mixing powder, the lanthanum nitrate solution and stearic acid solution was added into mixed powder, instead of La₂O₃ and graphite powder, because solution can make powder mixed evenly. On the other hand, lanthanum nitrate can produce La₂O₃ during the sintering process, and stearic (C₁₈H₃₆O₂) acid can be decomposed into C elements. These elements are produced by reaction, so that more uniform mixed in powder and finer, which is conducive to form solid solution strengthening and second phase strengthening. Further, stearic acid can act as a lubricant and release agent during pressing.

During mixing, using ethanol as a solid - liquid mixed media, can prevent and reduce powder oxidation. What’s more, stearic acid is insoluble in water, but it is soluble in alcohol.

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