Preparation of titanium and titanium alloy powder metallurgy process

Titanium metal and titanium alloys made by powder metallurgy. Titanium has high chemical activity and is easily contaminated by gases and crucible materials. Therefore, high-quality titanium powder is mainly produced using a centrifugal atomization powdering process under the protection of vacuum or high-purity inert gas. The products are generally formed without a binder, and the blank must be sintered in a vacuum.

In the late 1940s, research on the pressing and sintering process using titanium sponge powder as raw material was first carried out. However, the performance of the products produced by this process cannot yet meet the requirements of the aviation sector. It is mainly used to manufacture corrosion resistance, filtration and other parts required by chemical industry, light industry, metallurgy, ocean development and other sectors. The first product to gain industrial application was titanium porous filter material. In the mid-1960s, the process of producing titanium pre-alloyed powder by the rotating electrode method and hot isostatic pressing densification began to be developed. The static mechanical properties of the products produced by this process are equivalent to those of smelting products, but the cutting process is significantly reduced, the utilization rate of materials is improved, and it has begun to be used in the aviation industry. By the end of the 1970s, the application of titanium powder metallurgy products in corrosion resistance and aviation had developed rapidly. China began to conduct research on titanium powder metallurgy processes and products in the early 1970s. Titanium metal valves, sleeves, porous tubes and plates, titanium-titanium carbide wear-resistant materials, and titanium-molybdenum corrosion-resistant alloys have all been industrially produced. In the late 1970s, research was carried out on centrifugal atomization to produce high-quality titanium alloy powder and hot isostatic pressing forming technology.

1. Sodium reduction sponge titanium powder. This kind of powder has large output, low price, good powder plasticity, and is suitable for cold forming. It is the main raw material for the production of general corrosion-resistant products. Because it contains high sodium and chloride ions, it can easily contaminate equipment during sintering and worsen the welding performance of the material.

2. Electrolytic titanium powder. The purity is higher than that of sodium-reduced sponge titanium powder, but the formability of electrolytic titanium powder is worse than that of sponge titanium powder.

3. Hydrodehydrogenated titanium powder. Titanium powder and its alloy powder with good quality and fine particle size can be obtained through the hydrogenation and dehydrogenation process; however, the batch size is small and the price is relatively expensive.

4. Centrifugally atomized titanium powder. In the 1960s, the American Nuclear Metal Company first used the arc rotating electrode method to produce titanium pre-alloyed powder. The powder is spherical in shape. This kind of alloy powder has high purity, uniform composition, good fluidity, and a filling density of 65% of the theoretical value. This kind of powder is only suitable for hot forming, and parts with complex shapes can be made by hot isostatic pressing. In the arc rotating electrode powder making process, since one of the electrodes is a tungsten rod, it is easy to produce tungsten contamination (the tungsten content in the powder reaches 400ppm), which will reduce the fatigue performance of the material. In order to eliminate tungsten pollution, various centrifugal atomization powdering processes such as rotating electrodes, arc rotating crucibles, and electron beam rotating disks using electron beams or plasma as heat sources have been developed. This type of powder is the main raw material for manufacturing titanium powder metallurgy aerospace parts.

1. Sintering of loose or low-pressure forming powder blanks. The porosity of the sintered body is 25-70%, and this process is mostly used to produce porous titanium products and materials.

2. Pressing and sintering. Pressing can be done mechanically or isostatically. The pressing pressure is between 2000 and 4000kgf/cm2, and the sintering temperature is between 1000 and 1400°C. The relative density of the sintered body can reach 92-95%; this process is used to produce corrosion-resistant parts, general structural parts or ingots for processing.

3. Thermoforming. It is to pressurize the powder or powder ingot during the heating process. Thermal forming processes mainly include hot isostatic pressing, vacuum hot pressing, etc. Titanium alloy powder produced by centrifugal atomization is formed by hot isostatic pressing. The density of the product can be close to the theoretical density and the properties are uniform in all directions; high-performance aerospace structural parts are mainly produced by hot isostatic pressing. .

4. Powder rolling of titanium powder and powder blank. Extrusion and forging of blanks, etc. These processes can obtain titanium powder materials or parts with high density and good performance. Among them, powder rolling is an effective and economical processing technology for producing porous titanium plates and dense titanium plates.