X-ray tube with rotating anode target surface directly subjected to the bombardment of high-energy electron beam to emit X-rays, the local temperature can be as high as 2600℃. Tungsten has a high melting point, high temperature strength, good heat dissipation performance, high atomic number, and can stimulate strong X-rays under electron beam bombardment, so it is usually used as a target surface material. However, because the X-ray tube is intermittent work, when it is cold and hot, the target surface material is easy to crack, and tungsten has a notch-sensitive effect, which is easy to lead to the expansion and deepening of cracks, stripping from the matrix, and damaging the X-ray tube. Adding a small amount of rhenium and other precious metals in tungsten or other transition elements with high melting point and high plat number to form tungsten alloy as a target surface material has better melting loss resistance than pure tungsten target surface layer, preventing the crack of the target surface, ensuring clear imaging, and improving the service life of the X-ray tube. On the other hand, if pure tungsten is used as a target, the weight of the target increases when the diameter is increased to improve the heat capacity of the target due to the large ratio of tungsten. When rotating at high speed, the starting torque increases, the starting time increases, the excitation coil increases, and the bearing load increases, which is very unfavorable to the work of the X-ray tube. At the same time, due to the notch sensitive effect of tungsten, once the crack occurs, it develops rapidly, causing the overall damage of the target. To this end, it is necessary to use a kind of material that can be bonded with tungsten better into one, and can reduce the weight of the target and increase the heat capacity of the target as the matrix, molybdenum specific gravity is about 1/2 of tungsten, specific heat is more than twice of tungsten, and high temperature strength, can be bonded with tungsten into a solid whole, it is commonly used as the matrix material, the diameter of the same molybdenum base tungsten target than pure tungsten target weight reduction of about 1/2, The same weight molybdenum base tungsten target, the heat capacity increased by more than twice, increasing the output power of the target.
Tungsten-rhenium-molybdenum alloy has excellent properties such as fine grain, uniform structure, low content of impurity elements, high density and high strength. The rotating anode target for X-ray tube made of tungsten-rhenium-molybdenum alloy has the advantages of high product qualification rate, good heat dissipation, good thermal shock resistance and long service life.
The method of preparing tungsten-rhenium powder by direct mixing of tungsten powder and rhenium powder in prior art is given up, and the tungsten-rhenium pre-alloy powder with special ratio is prepared by mixing and reducing tungsten powder and ammonium rhenate powder, which is more uniform. On the other hand, through the hot isostatic pressing process, especially by selecting the appropriate hot isostatic pressing treatment temperature and pressure to achieve fine grains, increase the connection strength of tungsten rhenium and molybdenum alloy layer and the density of the workpiece.
