3D Printing Metal Powders

Overview

3D printing, also known as additive manufacturing (AM), utilizes metal powders to construct complex components layer by layer directly from digital models. The powders are selectively melted or bound by precision heat sources guided by the CAD model geometries.

Popular AM processes for metals include binder jetting, directed energy deposition, powder bed fusion, sheet lamination, and more. Each requires powder feedstock with specific characteristics to achieve optimal density, surface finish, dimensional accuracy, and mechanical properties.

This guide provides an in-depth look at metal powders for 3D printing, including alloy types, powder production methods, key powder properties, applications, specifications, suppliers, and purchasing considerations when sourcing material. Helpful comparison tables summarize technical data to assist with powder selection and qualification.

Connecting with knowledgeable suppliers of optimized 3D printing powders enables manufacturers to improve print quality, reduce defects, and fully leverage AM benefits like design freedom, faster iteration, and part consolidation.

Alloys for 3D Printing Powders

A wide range of metals and alloys are available in powder form suitable for AM processes:

Common Alloy Systems for 3D Printing Metal Powders

• Stainless steels
• Tool steels
• Titanium and titanium alloys
• Aluminum alloys
• Nickel superalloys
• Cobalt-chrome alloys
• Copper alloys
• Precious metals

Both standard and custom alloys can be sourced to meet specific application requirements in terms of corrosion resistance, strength, hardness, conductivity, or other properties.

Metal Powder Production Methods for AM

Additive manufacturing utilizes metal powders produced through:

Typical Metal Powder Manufacturing Methods for 3D Printing

• Gas atomization
• Water atomization
• Plasma atomization
• Electrolysis
• Carbonyl iron process
• Mechanical alloying
• Metal hydriding/dehydriding
• Plasma spheroidization
• Granulation

Spherical atomized powders provide optimal flow and dense packing needed for most AM processes. Some techniques allow nanoscale or customized alloy particles.

Key Characteristics of Metal Printing Powders

Critical powder characteristics for AM include:

Metal 3D Printing Powder Properties

Characteristic	Typical Values	Importance
Particle size distribution	10 to 45 microns	Affects densification, surface finish
Particle shape	Spherical	Improves flow and packing
Apparent density	2 to 4 g/cc	Influences bed density
Tap density	3 to 6 g/cc	Indicates compressibility
Hall flow rate	25-50 s/50g	Ensures smooth powder spreading
Loss on ignition	0.1-0.5%	Low moisture improves printing
Oxygen content	<0.1%	Minimizes microstructural defects

Precisely controlling characteristics like particle size, shape, and chemistry is critical to achieve fully dense AM parts with the desired mechanical properties.

Applications of 3D Printing Metal Powders

AM enables complex geometries impossible through conventional techniques:

Metal 3D Printing Applications

Industry	Uses	Benefits
Aerospace	Turbine blades, structures	Design freedom, weight reduction
Medical	Implants, prosthetics, instruments	Customized shapes
Automotive	Lightweighting prototypes and tools	Rapid iteration
Defense	Drone parts, protective structures	Quick prototypes and short runs
Energy	Heat exchangers, manifolds	Part consolidation and topology optimization
Electronics	Shielding, cooling devices, EMI	Complex enclosed structures

Lightweighting, part consolidation, and high-performance alloys for extreme environments provide key advantages over traditional manufacturing methods.

Specifications for 3D Printing Metal Powders

International specifications help standardize AM powder characteristics:

Metal Powder Standards for Additive Manufacturing

Standard	Scope	Parameters	Test Methods
ASTM F3049	Guide for characterizing AM metals	Sampling, size analysis, chemistry, defects	Microscopy, diffraction, SEM-EDS
ASTM F3001-14	Titanium alloys for AM	Particle size, chemistry, flow	Sieving, SEM-EDS
ASTM F3301	Nickel alloys for AM	Particle shape and size analysis	Microscopy, image analysis
ASTM F3056	Stainless steel for AM	Chemistry, powder properties	ICP-OES, pycnometry
ISO/ASTM 52921	Standard terminology for AM powders	Definitions and powder characteristics	Various

Compliance with published specifications ensures repeatable, high quality powder feedstock for critical applications.

Global Suppliers of 3D Printing Metal Powders

Leading international suppliers of AM-optimized metal powders include:

Metal Powder Manufacturers for 3D Printing

Supplier	Materials	Typical Particle Size
Sandvik	Stainless, tool steel, nickel alloys	15-45 microns
Praxair	Titanium, superalloys	10-45 microns
AP&C	Titanium, nickel, cobalt alloys	5-25 microns
Carpenter Additive	Cobalt chrome, stainless, copper	15-45 microns
LPW Technology	Aluminum alloys, titanium	10-100 microns
EOS	Tool steel, cobalt chrome, stainless	20-50 microns

Many focus on fine spherical powders specifically engineered for common AM methods like binder jetting, powder bed fusion, and directed energy deposition.

Purchasing Considerations for 3D Printing Metal Powder

Key aspects to discuss with metal powder suppliers:

• Desired alloy composition and properties
• Target particle size distribution and shape
• Envelope density and hall flowability
• Allowable impurity levels like oxygen and moisture
• Required testing data and powder characterization
• Available quantity range and lead times
• Special handling precautions for pyrophoric materials
• Quality systems and powder origin traceability
• Technical expertise in AM-specific powder requirements
• Logistics and delivery mechanisms

Work closely with suppliers experienced in optimized AM powders to ensure ideal powder selection for your process and components.

Pros and Cons of Metal 3D Printing Powders

Benefits vs Limitations of Metal Powders for AM

Advantages	Disadvantages
Allows complex, customized geometries	Higher cost than conventional materials
Shortens development time dramatically	Powder handling precautions required
Simplifies assemblies and lightweights	Post-processing often needed on as-printed parts
Achieves properties nearing wrought materials	Size and build volume constraints
Eliminates expensive dies, molds, tooling	Thermal stresses can cause cracking and distortion
Enables parts consolidation and topology optimization	Lower production volumes than traditional methods
Improves buy-to-fly ratio greatly	Requires rigorous powder characterization and parameter development

When used appropriately, metal AM provides game-changing benefits but requires expertise to implement successfully.

FAQ

How small can metal powder particle size be for AM?

Specialized atomization techniques can produce powder down to 1-10 microns, however most metals printers work best with minimum size around 15-20 microns for good flow and packing.

What causes poor surface finish in printed metal parts?

Surface roughness arises from partially melted powder adhered to surfaces, spatter, staircase stepping, and suboptimal melt pool characteristics. Using finer powders and dialing in ideal processing parameters smoothens finish.

Do all metal 3D printing methods work with the same powders?

While there is overlap, binder jetting generally uses a broader powder size distribution than powder bed fusion. Some processes are limited to certain alloys based on melting points or reactivity.

How are mixed or bimetallic powders made?

Prealloyed powders ensure uniform properties but for composites, physical powder blending or specialized atomization techniques provide blended elemental powder mixes.

How long does it take to change powder material in a metal printer?

A full purge and changeover between significantly different alloys requires 6-12 hours typically. Quick changes between similar materials can be under an hour.

Conclusion

Optimized metal powders enable additive manufacturing processes to construct complex, robust metal components with superior properties. Matching alloy chemistry and powder characteristics to the printing method and component performance requirements is critical to high quality results. By partnering with experienced powder suppliers, end users leverage expertise in both powder production and 3D printing processes to develop robust AM components faster and more reliably.

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