Which Metal Materials Can Be Considered for Metal 3D Printing Applications?

A design engineer selects a high-strength alloy from a materials handbook, orders powder of the same composition, and runs a build on a laser powder bed fusion system. The part cracks during the build. The alloy is strong in its wrought form, but its welding behavior is poor, and the rapid solidification of Metal 3D Printing concentrates the residual stress at the grain boundaries. The engineer learns that the handbook property is not the printing property. The material feasibility for additive manufacturing depends on the alloy weldability, the width of the process window, and the post-processing path. This guide explains which metal materials can be considered and how to qualify them.

1. Why Does Material Selection Start With the Process Rather Than the Property Data Sheet?

A materials handbook reports the properties of a wrought or cast alloy after a specific heat treatment. The same alloy in the as-built state of Metal 3D Printing has a different microstructure. The laser melts and solidifies the powder in microseconds, and the resulting grains are fine and strongly textured. The residual stress is high, and the defect population, including porosity and lack of fusion, depends on the process parameters. A data sheet that reports a tensile strength of 1,200 MPa for a wrought alloy tells nothing about whether the alloy will crack during printing. In our factory, we evaluate every alloy for its crack susceptibility, its process window, and its post-build heat treatment before we recommend it. Nextgen Advanced Materials INC has been developing metal powders for additive manufacturing for over 10 years.

The process window is the range of laser power, scan speed, hatch spacing, and layer thickness within which the part reaches full density without keyhole porosity or lack of fusion. A wide window is easier to productionize. A narrow window requires tighter powder and machine control and is more expensive to run. The third factor is the post-processing. Some alloys require hot isostatic pressing to close the internal porosity, and some require a specific heat treatment to relieve the residual stress and to precipitate the strengthening phase.

2. Which Steel Families Are Actually Printable and What Do They Trade Off?

The steel family is the most widely used in Metal 3D Printing because the alloys are weldable and the powders are available. The austenitic stainless steel 316L is the workhorse. It has good corrosion resistance and good ductility, and it prints with a wide process window. The martensitic precipitation-hardening steels 17-4PH and 15-5PH print well and can be strengthened by a post-build aging treatment. The tool steels H13 and 1.2709 are used for molds and dies. The 1.2709 is a maraging steel that achieves very high strength after aging. The table below compares the common printable steels.

The trade-off is between strength, corrosion resistance, and printability. The 316L is the easiest to print but has the lowest strength. The 17-4PH and 15-5PH have higher strength but require a post-build aging treatment and have a narrower process window. The tool steels and the maraging steel achieve the highest strength but require a hardening treatment and are more prone to cracking. In our factory, we recommend the alloy based on the part function and the post-processing capability of the customer.

3. When Do Aluminum, Titanium, and Nickel Alloys Make Sense?

The aluminum alloys used in Metal 3D Printing are mainly the casting alloys AlSi10Mg and AlSi7Mg. They have good castability and print with a wide window. They are used for lightweight brackets, heat sinks, and housings. The titanium alloy Ti-6Al-4V is used for its high specific strength and its biocompatibility. It is used in aerospace and medical implants. The nickel alloys Inconel 625 and 718 are used for their high-temperature strength and corrosion resistance. They are used in jet engine components and chemical processing. The table below shows the process constraints and applications of the three families.

4. Why Do Copper and Refractory Metals Remain Special Cases?

Copper and its alloys are difficult to print because they reflect most of the laser energy at the common wavelengths. The high thermal conductivity also conducts the heat away from the melt pool, which makes the melt pool unstable. The copper alloys are printed on machines with a green or blue laser, or with a high-power infrared laser and a special scan strategy. The refractory metals, such as tungsten, molybdenum, and tantalum, have very high melting points and are prone to cracking because of the residual stress and the oxygen pickup. They are printed on machines with a high-temperature build chamber and a controlled atmosphere. In our factory, we evaluate the copper and refractory alloys on a case-by-case basis and we recommend them only when the application justifies the cost and the risk.

The precious metals, such as gold and silver, are printed for jewelry and dental applications. The shape memory alloys, such as nitinol, are printed for medical devices. These are small-volume applications, but they are growing. The key is to match the powder and the process to the specific alloy and to validate the part with the mechanical and functional tests that the application requires.

5. How Should Engineers Qualify a Metal Powder and a Printing Route for a Given Part?

The powder qualification should include the particle size distribution, the sphericity, the oxygen content, the flowability, and the apparent density. The powder should be tested for the chemical composition and for the presence of satellite particles. The powder should be tracked through its reuse cycles, because the oxygen content and the particle size change with reuse. The process qualification should include the parameter development, the density measurement, the defect analysis by computed tomography, the tensile test, the fatigue test, and the dimensional inspection. In our factory, we provide a qualification package for each powder and each process. Nextgen Advanced Materials INC also provides a reuse study that shows the change in the powder properties after 10 cycles.

We recommend that the engineer qualify the powder and the process together. A powder that meets the specification may not print well on a machine with a different laser spot size or a different recoater. The qualification should be performed on the actual production machine with the actual powder batch.

Summary for Designers and Manufacturing Engineers

The metal materials that can be considered for Metal 3D Printing include the austenitic and precipitation-hardening stainless steels, the tool steels, the maraging steels, the aluminum casting alloys, the titanium alloy Ti-6Al-4V, and the nickel alloys Inconel 625 and 718. Copper and refractory metals remain special cases that require a specific machine and process. The selection should start with the process feasibility, not with the data sheet. The powder and the process should be qualified together on the production machine. Nextgen Advanced Materials INC has been developing metal powders for additive manufacturing for over 10 years and provides full material and process qualification support for our customers.