Niobium alloys are formed by adding a certain amount of hafnium and other elements to niobium. In a binary phase diagram, niobium and -hf form a displaced solid solution.
Hafnium is a kind of active element, which can be combined with oxygen and carbonation in niobium to form HfO2 and HfC compounds, which can play the role of dispersion enhancement, reduce the harmful effect of interstitial elements, and improve the weldability and coating properties of niobium alloys. Niobium hafnium alloy is the most widely used niobium alloy in aerospace engineering and technology.
In 1965, the United States successfully developed the nb-10hf-1ti alloy, which was used in 1969 for the extended nozzle section of the rocket engine of the Apollo manned lunar module descent stage. In 1975, China successfully developed it. Niobium alloy.
Niobium and nifnium alloys can be divided into two types according to the strengthening methods: solid solution strengthening alloys and alloys combining solid solution strengthening and dispersion strengthening.
Preparation methods, such as the preparation of the ingot blank plastic processing: niobium hafnium alloy usually adopt vacuum electron beam melting and the electricity arc smelting preparation method of combining the ingot blank, then at above 1200 ℃ temperature extrusion or forging breakdown, in under 500 ℃ under the temperature of rolling and drawing processing, can be made into plate, belt, rod, wire and forging products.
Welding: niobium hafnium alloy has good weldability. It usually adopts tungsten pole argon welding and electron beam fusion welding to realize the connection of parent metal. It can also use these two welding methods to complete the welding of niobium hafnium alloy with titanium and titanium alloy. The quality of the weld is related to the purity and vacuum degree of argon. Generally, the higher the purity of argon and the lower the residual atmospheric pressure, the better the quality of the weld.
Heat treatment: vacuum or inert gas protection annealing treatment and solid solution aging treatment are generally adopted.
Coating: cr-ti-si and cr-fe-si oxidation resistant coatings are usually used. Add these two kinds of coating of niobium hafnium alloy at 1371 ℃ in the air oxidation life in more than 150 h.
Application: mainly used for extended nozzle section and thrust chamber of radiant cooling nozzle of liquid rocket engine, molten sodium and sodium potassium alloy pressure pipe and turbo pump of space power generation system, high-temperature structural components of jet engine, etc.
