NanoSteel powder alloys advance 3-D printing of high-hardness parts

  • 23-Mar-2015 10:59 EDT
NanoSteel AM bearing.jpg

NanoSteel has proven the ability to generate 99.9% dense, crack-free parts. Shown is an integrated bearing built through laser powder bed fusion. (Click arrow at top right to view additional images.)

NanoSteel has expanded its additive manufacturing (AM) material capabilities to support metal 3-D printing of complex high-hardness parts and the ability to customize properties layer-by-layer through “gradient material design.”

The Providence, RI-based company has developed progressive generations of iron-based alloys during its 13-year history, and “within the last year has applied some of these designs in powder form specifically to additive manufacturing,” according to Harald Lemke, Vice President and General Manager of Powder Metallurgy.

The tendency of high-hardness metallic parts created through additive manufacturing to develop cracks has been a major obstacle in their development path. NanoSteel leveraged its 2014 breakthrough in AM wear materials and worked with global process development partners to print a bearing and impeller using the powder bed fusion process.

The resultant wear parts were measured to be fully dense and crack-free, with hardness levels >1000 HV. The parts’ wear resistance is comparable to conventionally manufactured M2 tool steels, according to NanoSteel, and they feature a uniform microstructure. These properties were achieved without the need for post-processing such as hot isostatic pressing (HIP) or further heat treatment, reducing production cost and lead times.

The company’s powders are unique due to their chemistries and microstructure, according to Lemke. “For example, in the additive manufacturing process, some of these chemistries create a uniform metal matrix composite structure which enables isotropic properties achieved during solidification without heat treatment.”

Building on the success of this wear-part demonstration, NanoSteel pursued the development of parts with a gradient design using a combination of high hardness and ductile alloys. The company worked with Connecticut Center for Advanced Technology within the past six months to generate part samples using freeform direct laser deposition. This single AM process achieved a seamless transition between the hard and ductile properties without subsequent heat treatment.

These gradient material designs offer the equivalent of “digital case hardening,” according to NanoSteel, delivering impact resistance and overall robustness in addition to high hardness and wear resistance in a single part. This capability offers OEMs considerable design flexibility in meeting part-performance requirements, according to Lemke.

“Proprietary metal alloys that support the cost-effective 3-D printing of high-quality parts will help accelerate the transition from subtractive to additive manufacturing across applications such as wear parts, bearings, and cutting tools,” said Lemke. “The company’s AM powder offerings make it possible to design exclusively for the function of a high-hardness part, releasing designers from the limitations of conventional production processes and opening new opportunities to improve performance.”

NanoSteel is currently seeking development partnerships with OEMs on specific application development, he added. “An overall product commercialization timeline will be developed as a result of these partnerships.”

Targeted markets for its AM powder portfolio include automotive and agriculture, as well as energy and tool and die.

“[Our] AM powder offering can be used for aesthetic and functional prototyping of automotive parts as well as next-generation lightweight solutions due to the higher performance compared to other carbon steels,” Lemke shared. For agriculture, “parts that traditionally have required hardfacing can benefit from the process flexibility of 3-D printing through the use of gradient material design.”

When released, the ferrous powders will be “very competitive” with other AM materials in terms of cost, he claims.

(Go to http://articles.sae.org/12968/ to read more on NanoSteel’s AHSS alloys.)

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