Fabrication of long tubular parts made of tungsten-heavy alloys by inductive bonding of multiple tubes

Abstract

The structural integrity of tungsten-heavy alloy (THA) powder compacts, shaped into long tubular parts with a high length-to-diameter ratio, are difficult to handle and break easily owing to the low strength of powder compacts and heaviness of THA powders. Furthermore, slumping that occurs during liquid-phase sintering may induce a dimensional distortion and degrade their mechanical properties. To overcome these difficulties, a method for fabricating long tubular parts by inductively bonding multiple unit tubes locally is proposed and characterized. Customized long tubular parts are fabricated by stacking straight and tapered unit tubes in a vacuum chamber and inductively bonding them to produce straight or tapered tubular parts. Bond strength essentially equals the strength of individual unit tubes. Inductive-bonding performance was estimated and optimized with respect to various process factors, including the environmental atmosphere, temperature, joining pressure, and rotational positioning of stacked tubes. The manufacturing process, amenable to industrial application, is well characterized, and its feasibility is demonstrated by a product free of gravity induced distortion and excellent bond quality, assessed in terms of microstructure and mechanical properties.