Evaluation of Additively Manufactured Ultrahard Steels

Recent advances in both alloy development and additive manufacturing have enabled the production of ultrahigh-strength steels in nearnet shape parts.

Army Research Laboratory, Aberdeen Proving Ground, Maryland

Ultrahigh-strength steels are traditionally defined as those steels with a minimum yield strength of approximately 1380 MPa. Notable examples of steels in this category include AISI 4130, AISI 4140, and AISI 4340. In many cases, maximizing the performance of these alloys requires a rather complex approach that involves a series of tempering, annealing, or stress-relieving treatments. As a result, they are produced using a variety of traditional processing methods such as casting, rolling, extrusion, or forging. These traditional methods - combined with the ultrahigh strength of the steels - often meant that the production of complex, near-net shape parts of high quality was quite difficult. In addition, these production methods often entailed repetitive treatments or long production cycles, both of which resulted in elevated production costs.

Additive manufacturing (AM, also known as 3D printing) has recently been recognized as a manufacturing method that enables the production of near-net shape parts. In these methods, a complex part is iteratively built in a layer-by-layer process that involves powder deposition followed by selective melting/sintering of the powder to form the part. With the continued development of processing lasers, it is now possible to form fully dense components from a wide range of metals powders, including refractory alloys, steels, and other high-temperature alloys.