Scientists delve into the details of how the mechanical properties of 3D-printed steel are improved through post-processing

Additive manufacturing, also known as 3D printing, can now be done using metals and is likely to become a crucial tool in many manufacturing fields. In recent in-depth studies, a team of scientists from Korea Maritime and Ocean University explores the effects of various post-processing methods and how they can be used to improve the mechanical characteristics of printed stainless steel.

Additive manufacturing, more commonly known as 3D printing, is an intersection between various engineering fields, including software, hardware, materials, and electromechanical engineering. Over the last few years, 3D printing and coating by melting metal powders has become a hot research topic; for example, metal powder can be used to produce or enhance parts for cars, ships, and planes. However, there are limitations to the surface quality and strength of the printed products, which have prevented the widespread application of these techniques thus far.

To extend the uses of directed energy deposition (DED), one of the most promising additive manufacturing techniques, it is necessary to understand not only how the printing conditions affect the mechanical properties of the final piece, but also how these properties can be enhanced through post-processing treatments.

In two recent studies, published in Materials Science and Engineering: A and the Journal of Materials Processing Technology, teams of scientists led by Dr Do-Sik Shim from Korea Maritime and Ocean University fill this knowledge gap by diving deep into DED and various post-processing techniques.

Dr Shim and teams began with the need to figure out how to enhance the mechanical properties of DED-layered 630 stainless steel, a metal regularly used in the automobile and aerospace industries. They conducted extensive analyses on samples of 630 stainless steel deposited through DED to understand exactly how different printing conditions affect the outcome. They also explored the effects of three post-processing treatments: two types of heat treatment, solution annealing and precipitation hardening, and a surface modification technique called ultrasonic nanocrystal surface modification (UNSM).

For their analyses, they employed advanced spectroscopy techniques, scanning electron microscopy (SEM), and a variety of mechanical tests. These allowed them to observe in detail the mechanical and microstructural changes and phase transitions induced by the post-processing treatments that lead to an improvement in strength, hardness, and surface quality, yielding methods for establishing high-quality additive manufacturing.

Speaking about the significance of their results, Dr Shim says: “Our studies present methodologies for precisely manufacturing high functional parts via 3D printing. They also provide basic data into the metallurgical and mechanical characteristics of 3D printed steel and will hopefully extend the adoption of DED in various industries, from automobiles and aircrafts to medical, architectural, and artistic fields.”

Additive manufacturing will certainly become a key player in our society in the near future, causing huge economic, social, and cultural ripple effects. Dr Shim also notes: “DED can be used to reuse damaged metallic parts, and highlights the positive environmental effect that repairing, instead of replacing, would have on the world.” On this note, he concludes that additive manufacturing will certainly become a strong ally in our quest to build a better future.

Reference

Authors:

(A) Wook Jin Oh (1), Yong Son(2), Seung Yeong Cho (1), Seung Weon Yang (2), Gwang Yong Shin (3), Do Sik Shim (1)

(B) Min-Seob Kim (1), Wook-Jin Oh (1), Gyeong-Yoon Baek (2,3), Yeong-Kwan Jo (4), Ki-Yong Lee (3), Sang-Hu Park (4), Do-Sik Shim (1)

Title of original papers:

(A) Solution annealing and precipitation hardening effect on the mechanical properties of 630 stainless steel fabricated via laser melting deposition

(B) Ultrasonic nanocrystal surface modification of high-speed tool steel (AISI M4) layered via direct energy deposition