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Open AccessArticle

Effect of Post-Heat Treatment on the AISI M4 Layer Deposited by Directed Energy Deposition

1
Smart Manufacturing Process Technology Group, Korea Institute of Industrial Technology, 9 Cheonmdan-venturero 108beon-gil, Buk-gu, Gwangju 61007, Korea
2
Department of Ocean Advanced Materials Convergence Engineering, Korea Maritime and Ocean University, 727 Taejong-ro, Yeongdo-Gu, Busan 49112, Korea
*
Authors to whom correspondence should be addressed.
Metals 2020, 10(6), 703; https://doi.org/10.3390/met10060703
Received: 10 April 2020 / Revised: 12 May 2020 / Accepted: 25 May 2020 / Published: 26 May 2020
(This article belongs to the Special Issue Additive Manufacturing of Metals with Lasers)
Currently, high-speed steel (HSS) powders are deposited locally on a metal surface through direct energy deposition (DED) onto hardface tool steel. Although the HSS powder enhances the hardness and the abrasion resistance of a metal surface, it makes the tool steel brittle because of its high carbon content. In addition, the steel is likely to break when subjected to a high load over time. This study focused on improving the steel toughness by applying a post-heat treatment. To fabricate a uniformly deposited layer through DED, M4 powder was deposited onto a pre-heated substrate (AISI D2). In addition, four post-heat-treated specimens were prepared, and their mechanical properties were compared. The Charpy impact and hardness tests were conducted to evaluate the durability required for the D2 die. The deposited M4 powder possessed a high hardness but a relatively low impact toughness. During laser melting, a stable bond formed between M4 and D2 without any cracks or delamination. The hardness of the initial M4 deposited layer was 63 HRC, which changed to 54–63 HRC depending on the effect of the post-heat treatment. Moreover, the post-heat-treatment process improves the impact toughness of the M4 deposited layer by changing its microstructure. View Full-Text
Keywords: directed energy deposition; post-heat treatment; toughness; hardness; AISI M4 directed energy deposition; post-heat treatment; toughness; hardness; AISI M4
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MDPI and ACS Style

Baek, G.Y.; Shin, G.Y.; Lee, K.Y.; Shim, D.S. Effect of Post-Heat Treatment on the AISI M4 Layer Deposited by Directed Energy Deposition. Metals 2020, 10, 703.

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