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TC4 Titanium Alloy Powder Metallurgy Vacuum Sintering

Taking the production of TC4 titanium alloy parts as an example, the production process of titanium alloy powder metallurgy is shown in the figure.

Sponge titanium is made into titanium powder by hydrogenation dehydrogenation (HDH), that is, titanium hydride obtained after hydrogenation of sponge titanium is crushed into powder, and then dehydrogenated in a vacuum furnace to obtain titanium powder. Add Al powder and V powder to titanium powder for alloying by high-energy ball milling. Since whether the powder raw material with fine particle size and controllable composition can be obtained plays a vital role in the performance of TC4 titanium alloy after vacuum sintering, it is necessary to control the particle size of titanium alloy powder at D50 not greater than 10 μm by high-energy ball milling. In addition, the high-energy ball milling should be carried out under the protection of argon, and the oxygen is strictly controlled during the whole process, so that the oxygen content of the final TC4 titanium alloy powder is lower than 0.12%.

Due to the high chemical activity of titanium, and the smaller the particle size of titanium powder, it is more likely to be polluted, especially by oxygen. Therefore, in order to control the oxygen content in the final product, the alloy powder after high-energy ball milling should be coated with an antioxidant for anti-oxidation treatment. The TC4 titanium alloy powder treated with anti-oxidation coating was subjected to cold isostatic pressing on a cold isostatic press. The cold isostatic press has an inner cylinder diameter of 630 mm and a height of 1500 mm. The maximum size of the product that can be pressed is 500 mm in diameter × 1100 mm. The mold material used is neoprene. The mold can be designed according to the size and shape of the final product, which can realize the near-net shape of the product to a certain extent, reflecting the unique advantages of less cutting and saving raw materials of powder metallurgy products.

Titanium alloy powder metallurgy vacuum sintering process

The TC4 titanium alloy blank after cold isostatic pressing is sintered in a vacuum sintering furnace. The vacuum sintering temperature is controlled between 1000 and 1300 ℃, and the vacuum degree is ≤2×10^-3Pa. After vacuum sintering, the relative density of TC4 titanium alloy parts can reach more than 99%, and it has excellent mechanical properties. It can be used directly as a load-bearing part, or as an extrusion billet to extrude a profile, or as a forging billet for forging parts with complex shapes.

In addition, the TC4 titanium alloy powder treated with anti-oxidation coating can also be axially pressed and formed with a steel mold on a hydraulic press, and then vacuum activated and sintered to obtain titanium alloy near-shaped parts with complex shapes.

Advantages of titanium alloy powder metallurgy vacuum sintering production

(1) Less investment in equipment

The powder metallurgy production process is short, the manufacturing equipment is small, the equipment investment can be flexibly allocated according to the production scale, and the total investment capital can be large or small, which is conducive to the technological transformation of titanium alloy manufacturing enterprises and the improvement of efficiency.

(2) High metal utilization rate

The use of powder metallurgy production technology can realize the near-net shape of titanium alloy, thereby significantly improving the utilization rate of raw materials and saving raw material costs.

(3) Good product performance

Tests have proved that the performance of TC4 titanium alloy powder metallurgy parts is higher than that of national standard forgings, and no forging modification is required.

(4) Low production cost

The production of titanium alloys by melting and forging requires several times of forging modification after 2 to 3 times of smelting. However, if the powder metallurgy near-net-shape titanium alloy is used as the blank, the final forging can be obtained by only one final forging, which saves the modified forging process of multiple upsetting and drawing of the ingot, which can shorten the production cycle of the product and significantly reduce the processing cost. It has absolute advantages for new product development and small batch production. the

In short, titanium alloy powder metallurgy vacuum sintering production ① less investment in equipment, flexible production scale configuration; ② fewer procedures, short process flow, short production cycle, low energy consumption, less pollution, is an energy-saving, environmentally friendly green production technology; ③ formed parts are near-net shape, less cutting, high material utilization rate, low cost, which is an effective way to reduce the price of titanium alloy parts; ④ product performance can reach or exceed the standard of aviation forgings. Therefore, the vacuum sintering production of titanium alloy powder metallurgy is an inevitable choice for the titanium industry to reduce production capacity and develop rapidly.