These include billet preparation and plasticity, welding, heat treatment and coating. Preparation of niobium - tungsten alloy ingots. 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 prealloyed strips, followed by more than two vacuum electron beam smelting or vacuum arc smelting or the combination of the two smelting methods.
The purpose of electron beam smelting is to remove impurities (such as interstitial elements, low melting point metal and nonmetallic impurities) from the prealloyed strips, control the alloy composition and prepare preformed ingots of a certain size.
The purpose of vacuum arc melting is to produce 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.
Tungsten niobium alloys are usually welded by inert gas tungsten electrode welding and electron beam welding, or by brazing with titanium and titanium alloys. Before welding, the welding metal must be cleaned with organic solvents such as CCl4 to remove grease and other stains, and the welding operation must be carried out in a high vacuum (vacuum degree less than 1). 333 x 10Pa) or high purity inert gas protection box.
The welding operation of niobium - tungsten alloy must be very careful. Stress relief annealing, recrystallization annealing and high temperature solution aging treatment are often used. When used in high temperature oxidation environment, must be coated with anti - oxidation coating.
Cr-Ti-Si and Cr-Fe-Si coatings are often used to obtain better oxidation resistance.The industrial niobium tungsten alloy has high strength at high temperature and good room temperature plasticity. It is mainly used for space shuttle skin, nuclear reactor engineering, jet engine parts and space power generation system thermal radiation screen and catheter.
