Zirconium, titanium molybdenum
Titanium zirconium molybdenum compost Mo-0.5, Ti-0. 08, Zr-0. 1 to 0. The presence of carbon leads to the formation of a dispersed phase of hard carbide, which strengthens the alloy. Using vacuum arc melting, powder metallurgy, etc. to process the alloy in industrial production, vacuum melting of the percentage (weight) of pure molybdenum, titanium, zirconium, etc.
TZM alloy manual maximum thickness is 5 mm, width 410 mm, length 1000 to 1500 mm, but TZM alloy plate is a long, complex process, equipment occupancy, consumption, low production, high cost, thus limiting its use; Powder metallurgy rules uniform mixing ratio with high purity molybdenum powder and THI2 powder, ZrH2 powder and spray carbon black powder cold isostatic pressing molding, high temperature sintering in a protective atmosphere after giving TZM dough. Blank, then through high temperature hot rolling (hot forging), high temperature annealing, high temperature annealing to relieve stress and temperature rolling (warm forging) of TZM finished material. The rolling (forging) process and subsequent heat treatment of steel billet have great influence on the properties and anisotropic structure of the material. Using POWDER metallurgy TZM alloy plate and bar processing, it can save the vacuum consumable arc furnace, large extruder and the corresponding high temperature furnace and other large equipment, simplify the process, shorten the production cycle, reduce energy consumption, capacity, the yield can be improved, thus greatly reducing the cost.
TZM alloy (superalloy) is a solid solution hardened and particle reinforced molybdenum base alloy. The development of a molybdenum-titanium solid solution and excellent dispersed titanium carbide provides good strength properties at temperatures up to 1400 ℃ for TZM recrystallization at temperatures of about 250 ℃, higher than molybdenum, which provides better weldability.
TZM alloy has higher recrystallization temperature, higher strength, hardness than non-alloy molybdenum at room temperature and high temperature and good ductility. In addition, TZM has good thermal conductivity, low vapor pressure, and good corrosion resistance, so it can be machined.
TZM molybdenum alloy sintering mainly hydrogen protection sintering and vacuum sintering, in the process of hydrogen protection sintering, due to the reduction of hydrogen, oxides in molybdenum powder will be reduced by hydrogen, so that the oxygen content in the material is reduced to dozens of μg/g below.
For molybdenum alloy with active elements such as titanium, zirconium, hafnium and niobium, the high activity of alloying elements will react with impurities in hydrogen to form oxides, nitride and hydride, resulting in high impurity content of molybdenum alloy, which seriously affects the mechanical properties of molybdenum alloy. Vacuum sintering can effectively reduce the content of oxygen, nitrogen and other impurities in these molybdenum alloys. In the process of vacuum sintering, slightly excessive carbon elements are generally added (relative to the established composition), and deoxidation is carried out through the reduction of metal oxides by carbon elements.
The metal oxide in the carbon reduction system generates metal carbide and CO, and the disproportionation reaction of Mo and MoO2 generates metal Mo and MoO3 gas under high vacuum temperature. These two reactions are the main deoxidation mechanism in vacuum sintering process.
TZM alloy billet was prepared by traditional powder metallurgy method. TiHx and ZrHx were added into molybdenum powder by mass fraction of 0.5% and 0.09%, respectively. Then 0.04%, 0.07% and 0.10% carbon black were added into the sample, and powder was mixed in v-type mixing machine. The oxygen content of mixed molybdenum alloy powder was measured.
The oxygen content and carbon content in vacuum sintered TZM molybdenum alloy were measured by pressing φ 50mm rod with 2.0 T isostatic pressure at 1940 ℃. The oxygen element in molybdenum powder is mainly determined by the oxygen content of molybdenum powder. Although the oxygen content in various alloy powder is high, it has little effect on the oxygen content in molybdenum alloy powder because of the small total content.
The common methods of preparing TZM alloy are arc melting - casting and powder metallurgy. Arc melting - casting method is to melt pure molybdenum by arc and add a certain amount of alloy elements such as Ti and Zr by weight percentage, and then use conventional casting method to get TZM alloy.
The principle of powder metallurgy is to mix high purity molybdenum powder with THi2 powder, ZrH2 powder and graphite powder in proportion and then through cold isostatic pressing, and then sintering at high temperature in a protective atmosphere to get TZM blank. After high temperature hot rolling (high temperature forging), high temperature annealing, medium temperature hot rolling (medium temperature forging), medium temperature annealing to eliminate stress, and then warm rolling (warm forging) to get TZM finished material. The rolling (forging) process and subsequent heat treatment of billet have a great influence on the properties, anisotropy and texture of the material.
TZM alloys are usually prepared as rods and plates. Powder metallurgy can save vacuum consumable electric arc furnace, large extruder and forging hammer as well as the corresponding high temperature heating furnace and other large equipment, so that the process is simplified, the production cycle is shortened, consumption is reduced, production capacity and product rate can be improved, so the cost is greatly reduced.
