ORIGINAL ARTICLE Wear resistance of direct-energy–deposited AISI M2 tool steel with and without post-heat treatment Young Keun Park 1,2 & Kyeongsik Ha 1 & Kwang Yong Shin 3 & Ki Yong Lee 3 & Dong Joo Kim 4 & Se-Hun Kwon 2 & Wookjin Lee 1,2 Received: 23 March 2021 /Accepted: 14 July 2021 # The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature 2021 Abstract In this study, the wear resistance of AISI M2 high-speed tool steel produced using direct energy deposition (DED) was investigated in detail. Wear behavior was studied under different wear loads and sliding speeds using ball-on-disk tribology tests with two different counterpart balls (bearing steel and ZrO 2 ). The wear test results revealed that there was almost no wear damage in the M2 alloy when a bearing steel counterpart ball was used. When a ZrO 2 ball was used as the counterpart, a measurable, but small, amount of wear weight loss of M2 was observed. It was found that M2 alloy fabricated by DED has excellent wear resistance, greater than fully carburized conventional steel and high wear resistance steel produced by DED. The formation of a lubricious tribo-oxide film on the worn DED M2 surface is likely the reason for its excellent wear performance. The total wear weight losses of only ~1.5 mg was observed for the M2 produced by the DED, both in the as-DEDed and heat treated states against ZrO 2 balls, under the wear loading conditions of 50 N wear load, 100 mm/s sliding speed and total sliding distance of 500 m. In comparison to the other wear- resistance materials, the wear weight loss of the M2 produced by the DED was more than 6 times smaller than the fully carburized structural steel and 1.5–4 times smaller than high wear resistance steel produced by the DED. Thus, DED of the M2 alloy offers a great potential for the production of wear-resistance hard-facing of tribological components. Keywords Direct energy deposition . Additive manufacturing . AISI M2 . Wear . Heat treatment 1 Introduction 1.1 Direct energy deposition (DED) DED is an additive manufacturing technique used for fabri- cating metallic components with complex three-dimensional geometries from computer-aided design data. DED uses powdered metal to deposit layers onto a given substrate with laser irradiation. During the deposition process, thermal ener- gy provided by a high-power laser beam produces a melt pool on the substrate or the previously deposited DED layer. Simultaneously, metal powder is supplied by a focused gas- powder jet directly to the melt pool. The laser beam and melt pool move in a pre-defined layer track pattern to produce each DED layer. This process is repeated to assemble a desired three-dimensional structure, layer by layer [1, 2]. 1.2 State of the art of DED hardfacing One of the main advantages of the DED process over other metal AM techniques, such as the selective laser melting pro- cess, is that deposition of a three-dimensional object on a complex shaped substrate is possible [3–5]. This makes the DED process appropriate for adding hard layers on existing metallic components, e.g., hardfacing local surface areas of tribological components and repairing worn or broken com- ponents [6, 7]. In addition, it is easy to obtain a high molding density with few pores, and it has a process characteristic of * Se-Hun Kwon sehun@pusan.ac.kr * Wookjin Lee wkjinlee@kitech.re.kr 1 Dongnam Division, Korea Institute of Industrial Technology (KITECH), Yangsan 50623, Republic of Korea 2 Department of Materials Science and Engineering, Pusan National University, Busan 46241, Republic of Korea 3 Seonam Division, Korea Institute of Industrial Technology (KITECH), Gwangju 61007, Republic of Korea 4 Technical R&D Center, Seo Yeong Co., LTD., Busan 46744, Republic of Korea The International Journal of Advanced Manufacturing Technology https://doi.org/10.1007/s00170-021-07741-9