Metal 3D Printing Materials

Steel is the most common metal used in 3D printing. Its excellent material properties, versatility, and broad use in precision manufacturing make 3D printing steel an excellent option for creating high quality parts. Most types of steel can be printed, but the two types most commonly used are stainless steels and tool steels — metals that are more expensive and difficult to fabricate conventionally.

Positive attributes:

• excellent strength and stiffness
• wide variety of material properties
• heat treatable.

Stainless steels are strong, stiff steels that possess excellent corrosion resistance due to their significant chromium content (at least 12%, often up to 18%). Two types of stainless steels are commonly printed: austenitic and martensitic.

• Austenitic stainless steels, the most common type of stainless steels, are corrosion resistant and can be both machined and welded, though they cannot be heat treated. 316L is common 3D printed stainless steel known for its superior corrosion resistance.
• Martensitic stainless steels are much harder than austenitic steels, but more brittle and less corrosion resistant. 17-4 PH is a martensitic stainless steel that can be heat treated to fit a variety of material properties and is broadly used throughout manufacturing.

Tool steels are named for their central application – tooling of all varieties. They contain carbide, an extremely hard compound that’s critical to their ability to cut, grind, stamp, mold, or form. Generally, they’re very hard, abrasion resistant, and many are usable at high temperatures. The three types most commonly metal 3D printed are A series, D series, and H series tool steels.

• A Series tool steels are great general-use, machinable tool steels that balance wear resistance and toughness. There are eight varieties of A Series, the most common of which is A2 tool steel. It’s a versatile, cold-work tool steel often used to make punches and dies, as well as a wide variety of other applications.
• D Series tool steels are optimized for wear resistance and hardness. They’re not particularly tough and are only used for cold work applications. The most common variety in the D Series is D2 steel, a cold-work tool steel used for all kinds of cutting tools, from blades to industrial cutting tools and knives.
• H Series tool steels cut and shape material at high (or cycling) temperatures. H13 is the most common 3D printed hot-work tool steel. Its mix of excellent 3D printed metal strength, toughness, wear resistance, and heat resistance make it a good general use tool steel that’s optimized for use in high temperatures.

3D metal printing technology differentiates itself by being able to fabricate high-value alloys at relatively low costs. Often difficult and expensive to machine, 3D printing enables companies to produce high-performing parts more affordably than subtractive methods. Superalloys thrive in adverse environments — places with high heat, corrosive chemicals, or both. Though there are many printable superalloys, the two most common groups are Inconel and Cobalt Chrome.

Positive attributes:

• Excellent mechanical properties
• Heat resistant
• Good surface stability
• Corrosion resistant
• Biocompatible (Cobalt Chrome only)

Inconel
The most common proprietary nickel alloy group is Inconel. This extremely strong, tough, and corrosion-resistant material is used in turbines, engine seals, and
rockets. The two formulations most used in 3D printing inconel are the stronger, tougher Inconel 718 and the more heat-resistant Inconel 625. Both are expensive
to machine conventionally, making 3D printing a cost-effective alternative.

Cobalt Chrome
This superalloy is known for its biocompatibility, high strength-to-weight ratio, and corrosion resistance; it’s essentially a higher grade, denser, more expensive version of Titanium. Like Inconel, it’s used in turbines and other hostile environments but can also be used in medical applications for which Inconel isn’t suitable, including orthopedic and dental implants.

While not a common material used in conventional fabrication, titanium’s strength to weight ratio and high cost (both material costs and machining costs) make it a great choice for 3D printing. Titanium is typically printed in two different varieties: Titanium alloys and pure Titanium (know as CP Ti).

Positive attributes:

• Strength-to-weight ratio
• Heat resistant
• Chemical resistant
• Biocompatible (process and alloy dependent)

Titanium Alloys
Titanium achieves its best mechanical qualities when alloyed with other metals. The most common titanium alloy is Ti64 (Ti-6Al-4V) — a material stronger and 40% less dense than 17-4 PH stainless steel. It excels in corrosive and high temperature environments. These traits make it a top choice in industries where high strength-to-weight ratio is valued, like aircraft and high performance vehicles.

Commercially Pure Titanium (CP Ti)

Pure titanium isn’t as strong as most titanium alloys, but it’s highly biocompatible. It’s used for orthopedic inserts and similar medical applications.

Copper presents a completely unique value among 3D printable metal materials — it’s used for its thermal and electrical conductivity instead of its mechanical properties. Metal 3D printing allows engineers to create geometrically optimized copper parts like heat sinks, welding arms, and bus bars for a far lower cost. There are only a few systems capable of printing any version of copper today. Copper can be printed in its pure form or more commonly in its alloyed form.

Positive attributes:

• Electrically conductive
• Thermally conductive
• Corrosion resistant
• Ductile

Pure Copper
Pure copper has the best thermal and electrical conductivity of any copper alloy,
making it the preferred option. However, due its high conductivity and high laser
reflectance, copper is incompatible with standard laser based systems. Pure
copper is only available on Bound Powder Extrusion machines.

Alloyed Copper
Alloyed copper typically contains 1-2% of alloying elements, which make it
printable on some Powder Bed Fusion machines. These alloys, while still relatively
conductive, are inferior options to pure copper. An example of printable alloyed
copper is C18150, an alloy with chromium and zinc.

Aluminum, while used in some metal 3D printers, is seen far less in 3D printing than in conventional manufacturing processes. Its scarcity in 3D printing metal parts is due to two factors: low printability and relatively low costs in conventional fabrication. As a result, the potential ROI for 3D printed metal parts using aluminum, or the metal 3D printer price, is not always in favor of printing. Most common Aluminum alloys – like 6061 and 7075 – are not printed. Instead, Powder Bed Fusion machines that print aluminum typically print softer, casting grade aluminums. These casting grade alloys contain up to 12% silicon by weight and have inferior mechanical properties.

Positive attributes:

• Low weight
• Durable
• Ductile

Because the value of printing is relatively low, it’s not clear when it will become commonplace in 3D printing. Until then, titanium and steel provide similar strength-to-weight ratios when printed with open cell infill, while continuous composite 3D printers can produce aluminum-strength parts for a fraction of the cost.

Organizations interested in 3D printing aluminum parts should consider additive manufacturing with Markforged Carbon Fiber 3D printing — which can create parts with strengths equivalent to 6061-T6 aluminum, while offering enhanced material properties such as stiffness, impact resistance, heat resistance, and durability. Furthermore, compared to 6061 aluminum, reinforced Carbon Fiber manufacturing offers dramatically improved strength-to-weight ratios, which can be critical for certain high-performance applications in industries such as aerospace and automotive.