Die-less manufacturing of tube by diffusion bonding of unit rods made of tungsten heavy alloy

A die-less method to manufacture tubes by diffusion bonding of rods made of tungsten heavy alloys was developed and characterized. Tungsten heavy alloys are pseudo-alloys of tungsten (W) with small amounts of lower-melting-point binder metals, typically Ni and Fe, and they are widely used in tubular shapes. Due to the excessively high consolidation temperature for W, the fabrication of components is normally done by sintering of powder compacts. During the sintering of W–Ni–Fe alloys, the partially melted Ni–Fe binder metal wets the tungsten powder particles and provides a soluble diffusion network for rapid sintering. However, as the binder metals partially liquefy, this process results in gravity-induced slumping, leading to distortion near the bottom section of the tubular part. This gravity-induced slumping creates significant difficulties during the production of tubular structures. A rod shape is the most stable shape to avoid slumping during sintering. Thus, a method to manufacture tubular tungsten heavy-alloy parts via joining of sintered rods by diffusion bonding was developed. Using an analytical model, the dimensions of the unit rods for fabrication of the target tube shape have been designed. An industry-applicable tube manufacturing process was well characterized, and the feasibility of the process was confirmed.