3D-Printing Metallic Feedstocks

Metallic AM Feedstock

The metallic starting material supplied to an additive manufacturing process, commonly in the form of powder, wire, or foil.

Three Major Metallic AM Feedstock Forms

Powder, wire, and foil.

Why are metallic AM feedstocks generally small or thin?

Additive manufacturing builds parts in layers, so metallic feedstocks are supplied in forms such as powders, wires, or thin foils that can be progressively deposited or consolidated.

Powder Feedstock

Metal supplied as small particles for use in additive manufacturing processes such as powder bed fusion, directed energy deposition, binder jetting, material extrusion, material jetting, and cold spray.

Wire Feedstock

Metal supplied as wire; it can be used by directed energy deposition and certain other AM processes.

Foil Feedstock

Metal supplied as thin sheet or foil; it is used in sheet lamination processes.

Powder Bed Fusion (PBF) Feedstock

Powder.

Sheet Lamination (SL) Feedstock

Sheet or thin foil.

Directed Energy Deposition (DED) Feedstocks

Powder or wire.

Binder Jetting (BJP) Feedstock

Powder.

Cold Spray (CS) Feedstock

Powder.

Why does feedstock manufacturing matter in AM?

The way a feedstock is manufactured can affect its characteristics and therefore its subsequent behavior during additive manufacturing.

Ingot

A cast simple shape, such as a cylindrical metallic form, suitable for subsequent processing into products such as bar or wire.

General Wire-Manufacturing Sequence

Cast an alloy ingot → progressively reduce its size through forging and bar processing → pull the smaller bar through dies until the desired wire diameter is obtained.

Wire Drawing

The process of pulling metal through a series of dies to progressively reduce its diameter until the desired wire size is achieved.

Drawing

A cold-working process used to progressively reduce the diameter of metallic wire by pulling it through dies.

Cold Working

Plastic deformation of a metal below temperatures associated with hot working; during wire drawing it progressively strengthens the metal and reduces its ductility.

Effect of Wire Drawing on Strength

Progressive cold working during drawing increases the strength of the metal.

Effect of Wire Drawing on Ductility

Progressive cold working during drawing reduces the ductility of the metal.

Why are intermediate anneals used during wire drawing?

Intermediate annealing reduces the strength produced by cold working and restores ductility so that further drawing can be performed.

Intermediate Anneal

A heat treatment performed between deformation steps to reduce strength and restore ductility, allowing additional cold working.

Wire Drawing Processing Relationship

Cold drawing → increased strength and decreased ductility → intermediate annealing → restored ductility → additional drawing.

Why may reactive or difficult-to-work alloys require repeated drawing and annealing?

They may reach the limit of their ductility during drawing, requiring annealing before further diameter reduction can continue.

Surface Cleaning During Wire Manufacturing

Lubricants and oxide coatings may be chemically removed during wire production.

Copper-Coated Welding Wire

Some arc-welding wires receive a thin copper coating to conduct electricity from the weld electrode to the wire.

Why can a copper coating matter when selecting AM wire?

If a copper coating is not desired for the intended application, care must be taken when ordering wire because some welding wire is supplied with this coating.

Foil Manufacturing

The production of thin metallic sheet by progressively reducing flat material in thickness using rolling rather than drawing round material through dies.

Rolling Mill

A machine that reduces the thickness of metal by passing it between rolls.

Why can foil manufacturing require intermediate annealing?

Like wire drawing, repeated thickness reduction can require intermediate anneals to restore sufficient ductility for further processing.

Wire Manufacturing vs. Foil Manufacturing

Wire is progressively reduced in diameter primarily by drawing through dies, whereas foil is progressively reduced in thickness by rolling.

Feedstock Form–Process Relationship

Different additive manufacturing processes require feedstocks with physical forms and dimensions compatible with how material is delivered and each layer is created.