Tungsten is an effective strengthening element of niobium, but with the increase of tungsten content, the plasticity and brittleness transition temperature of the alloy will increase, and the grain size will grow significantly. Therefore, in order to obtain high-strength niobium-tungsten alloy, it is necessary to appropriately control the amount of tungsten addition, and at the same time, appropriate amount of elements such as zirconium and hafnium, which refine grain and reduce the brittle transition temperature of plasticity, should be added. 1961 the United States developed the nb-10w-2 for use in the skin of the space shuttle. 5Zr alloy, later developed into Nb-10W-1Zr-0. 1 c alloy. China also developed it successfully in the early 1970s. 5 and NbWl0Zr1C0. 1 alloy.
Niobium - tungsten alloys are often prepared by powder metallurgy and smelting. Powder metallurgy is the preparation of ingots by mixing, pressing and sintering niobium, tungsten and other elemental powders into prealloy strips, and then using more than two vacuum electron beam smelting or vacuum arc smelting or combining the two smelting methods. The purpose of electron beam melting is to remove impurities (such as interstitial elements, low melting point metal and non-metallic impurities) in the prealloy bar, control alloy composition and prepare a certain size of ingot. The purpose of vacuum arc melting is to prepare ingots with more uniform composition, finer grain and larger diameter. Ingot billet machining after squeezing breakdown and forging temperature above 1200 ℃, and then under 500 ℃ temperature rolling, drawing, to the preparation of bar, sheet, strip, wire, etc.
When used in high temperature oxidation environment, it must be coated with antioxidant coating. Cr-Ti-Si and Cr-Fe-Si coatings are often used to obtain better oxidation resistance. Niobium tungsten alloy has high strength at high temperature and good plasticity at room temperature. It is mainly used in space shuttle skin, nuclear reactor engineering, jet engine parts and space power generation system thermal radiation screen and pipe.
