Analysis of molybdenum hafnium carbon alloy
Like molybdenum titanium zirconium alloy (TZM molybdenum alloy), molybdenum hafnium carbon alloy (MHC alloy) is also a kind of high temperature alloy with transition metal molybdenum as the main raw material. However, because of the different auxiliary materials, the physical, mechanical, chemical, machinable, recrystallization and other characteristics of the two are different.
MHC alloy belongs to particle reinforced molybdenum alloy, containing about 1.2% hafnium (Hf) and 0.05-0.12% carbon (C). Its properties are not only related to the particle size, particle size distribution and dosage of the constituent materials, but also related to the degree of processing deformation, heat treatment conditions and oxygen content. Under normal conditions, the more uniform the size distribution of the raw material carbide, the better the heat resistance and creep resistance of the alloy. In Mo-1Hf-0.05C alloy, the tensile strength of the spindle made by powder metallurgy is 20% higher than that of TZM alloy at 950-1250℃, and the directional elongation is about 10%, when the forging deformation reaches 60%.
In addition, because the oxygen in the molybdenum base alloy is easy to combine with the strengthening element hafnium, the hafnium oxide particles are larger, it is difficult to disperse uniformly, and it is easy to form the crack source. In general, the higher the oxygen content in an MHC alloy, the higher the plasticity-brittleness transition temperature and the lower the recrystallization temperature of the alloy, which in turn leads to the poorer toughness and machinability of the alloy. On the contrary, the alloy performance is better.
(1) smelting method: in the vacuum environment will be pure molybdenum and a certain amount of hafnium, carbon element smelting, you can get the required alloy products. The method can reduce the oxygen content of MHC alloy to 30ppm or even less than 20ppm, but there are disadvantages such as coarse alloy grain, complex process, low yield and high cost.
(2) powder metallurgy method: molybdenum powder, hafnium powder or hafnium hydride powder and carbon powder according to a certain proportion of uniform mixing, after static compression forming, sintering, rolling (forging), annealing can get the product. Although the alloy produced by this method has fine grains, simple production equipment, short production cycle and high yield, there is a shortage of oxygen content in the alloy.
Molybdenum hafnium carbon alloy use
Due to its excellent high temperature resistance, the alloy is widely used in X-ray tube rotating anode target, composite target base target, high temperature crucible, hot forging die, molten zinc treatment, rocket booster, sintering vessel, electronic devices and high temperature ceramic pad.