Wire used as a raw material for additive manufacturing processes in such a way that the amount of gaseous and/or volatile impurities in it is reduced or minimized. As used herein, the term "volatile element" refers to an element whose boiling point is below the nominal melting point of most wires. For example, concentrations of elements such as oxygen (O), sodium (Na), magnesium (Mg), phosphorus (P), sulfur (S), potassium (K), calcium (Ca), and antimony (Sb) can be maintained at concentrations below 20ppm, below 10ppm, below 5ppm, below 3ppm, and below 10 PPM.
Concentrations below 2ppm, or even below 1ppm (all concentrations herein are measured by weight unless otherwise indicated), and in embodiments of the present invention, one or more or even all of these elements may be volatile elements. The precursor wire itself may consist of, substantially consist of, or consist of one or more refractory metals such as niobium (Nb), tantalum (Ta), rhenium (Re), tungsten (W), and/or molybdenum (Mo). The wire can be used in additive manufacturing processes to form three-dimensional components such as refractory crucibles.
The precursor wire is manufactured, at least in part, by arc melting in a vacuum or essentially inert environment. The arc melting process beneficially minimizes or reduces the concentration of volatile impurities in the wire, making it possible to use the wire for successful additive manufacturing processes. The resulting wire is used in an additive manufacturing process to form a three-dimensional component composed at least in part of the precursor material. In an exemplary embodiment, a wire is fed towards a movable platform, and the front end of the wire is melted by, for example, an electron beam or a laser. The platform (and/or wire) moves so that the melted wire paints a pattern of essentially two-dimensional slices of the final part; In this way, the final component is manufactured in a layer-by-layer manner through the melting and rapid solidification of the wire. In this additive manufacturing process, the wire is successfully melted during the formation of the three-dimensional part with minimal (if any) sparks, bubbling, and/or splashing. In addition, the finished parts have a high density (e.g., greater than 96% of the theoretical density, greater than 97%, greater than 98%, or even greater than 99%), and there are no pores or cracks that can be associated with the use of conventional powder metallurgy raw materials, especially refractory metals.
The wire according to the embodiment of the invention can also be used in a variety of different wire feeding welding applications (e.g. MIG welding, welding repair), where an arc strikes between the wire and the workpiece, causing a part of the wire to fuse with the workpiece.
