The NanoSteel Co., a maker of nanostructured steel materials design, announced the successful expansion of the company's engineered powders business into additive manufacturing. By leveraging its uniform metal matrix microstructures in the laser sintering process, the company was able to build a crack-free, fully dense bulk sample. NanoSteel's initial focus in additive manufacturing supports the market need for on-demand, on-site wear parts while addressing the current challenges in 3D printing of high-hardness parts.
NanoSteel's breakthrough overcomes one of the major hurdles to achieving a high-hardness metallic part through additive manufacturing—the tendency to develop cracks during part builds. The company worked with a global process development partner to optimize processing of a proprietary NanoSteel alloy with a high volume fraction of borocarbide phases.
This successfully produced a fully dense (99.9%) crack-free part with hardness values over 1000 HV, wear resistance comparable to conventionally manufactured M2 tool steels, and a uniform microstructure. Importantly, these properties were achieved without the need for post-processing such as hot isostatic pressing (HIP) or further heat treatment, reducing production costs and lead times.
"We used a powder that was one on the hardest materials in our portfolio that still had some toughness, because I wanted to see how far I could push it," said Harald Lemke, NanoSteel's General Manager of Engineered Powders. "When you go to harder powders, cracks form very easily, which is one reason the tooling industry uses maraging steel for additive manufacturing. It's very highly alloyed and very expensive, with high ductility—very little wear resistance. Many plastics are abrasive because they contain fillers, which means the maraging steel will wear down very fast."
Working with a world class partner, Lemke explained that NanoSteel was able make a simple geometry part that was several inches large. "It was so dense that we didn't have pores," Lemke told PlasticsToday. "If you have pores in a water-cooled mold with conformal cooling channels, you could have water leakage and will definitely have a weakened mold. A density of over 99.9% is needed to prevent pore related issues."
The next step that Lemke said NanoSteel is working on now that they have demonstrated the density issue in a high-wear-resistant material, is to move on to high-complexity parts . "Currently the material options to produce highly wear-resistant parts through additive manufacturing are limited," said Lemke, "By extending the reach of steel into markets currently served by WC-Co., ceramics, and other nonferrous metal matrix-metal composites, NanoSteel has the potential to generate cost-efficient wear parts to serve the tooling, mining, energy, and transportation industries in applications such as pumps, bearings, and cutting tools."
The company is currently extending this breakthrough into more complex geometries and broadening its property sets to fully validate the market potential for 3D-printed steel components.
"We have a few moldmakers interested in what we can do with these ferrous based alloys. I believe there is room for improvement and that's where we're headed."
Moldmakers can realize several benefits to making cores and cavities using the 3D process, Lemke pointed out. "They can make molds much faster and save time, realize more complex geometries, and regulate cooling rates more precisely and have greater mold life," Lemke said. "With regard to inventory, you don't have to keep spare mold cores and cavities around on the shelf. You can print a new mold as it's needed."