Researchers Share 3D-Printing of 17-4 PH Stainless Steels

A microscopic image of 3D-printed 17-4 stainless steel. The colors in the left-side version of the image represent the differing orientations of crystals within the alloy. 

For airliners, cargo ships, nuclear power plants and other critical technologies, strength and durability are essential. Therefore, many contain a remarkably strong and corrosion-resistant alloy called 17-4 precipitation hardening (PH) stainless steel. A team of researchers from the National Institute of Standards and Technology (NIST), the University of Wisconsin-Madison and Argonne National Laboratory has identified particular 17-4 steel compositions that, when printed, match the properties of the conventionally manufactured version. The researchers’ strategy is based on high-speed data about the printing process they obtained using high-energy X-rays from a particle accelerator. 

The new findings could help producers of 17-4 PH parts use metal AM to cut costs and increase their manufacturing flexibility. The approach used to examine the material in this study may also set the table for a better understanding of how to print other types of materials and predict their properties and performance.

Despite its advantages over conventional manufacturing, metal AM of some materials can produce results that are too inconsistent for certain applications. Metal AM is particularly complex, in part because of how quickly temperatures shift during the process.

“When you think about additive manufacturing of metals, we are essentially welding millions of tiny, powdered particles into one piece with a high-powered source such as a laser, melting them into a liquid and cooling them into a solid,” said NIST physicist Fan Zhang, a study co-author. “But the cooling rate is high, sometimes higher than one million degrees Celsius per second, and this extreme nonequilibrium condition creates a set of extraordinary measurement challenges.”

The authors of the new study aimed to shed light on what happens during the fast temperature changes and find a way to drive the internal structure toward martensite.