Abstract
In this work, a highly alloyed cold work tool steel, Uddeholm Vanadis 4 Extra, was manufactured via the electron beam melting (EBM) technique. The corresponding material microstructure and carbide precipitation behavior as well as the microstructural changes after heat treatment were characterized, and key mechanical properties were investigated. In the as-built condition, the microstructure consists of a discontinuous network of very fine primary Mo- and V-rich carbides dispersed in an auto-tempered martensite matrix together with ≈15% of retained austenite. Adjusted heat treatment procedures allowed optimizing the microstructure by the elimination of Mo-rich carbides and the precipitation of fine and different sized V-rich carbides, along with a decrease in the retained austenite content below 2%. Hardness response, compressive strength, and abrasive wear properties of the EBM-manufactured material are similar or superior to its as-HIP forged counterparts manufactured using traditional powder metallurgy route. In the material as built by EBM, an impact toughness of 16–17 J was achieved. Hot isostatic pressing (HIP) was applied in order to further increase ductility and to investigate its impact upon the microstructure and properties of the material. After HIPing with optimized protocols, the ductility increased over 20 J.
Highlights
Metal additive manufacturing is gaining interest in industries such as tooling, which is mainly due to the possibility to manufacture complex shapes, which allow for the fabrication of intricate internal cooling channels, and at the same time to achieve fine microstructures
There is a lack of investigations focusing on high carbon cold-work tool steels, and just a few reports can be found in the literature, where only one example refers to the use of additive manufacturing (AM) in the production of worm-milling cutters [15,16,17]
As-built specimens were manufactured with a microstructure consisting of discontinuous carbides, which is characteristic of eutectic solidification
Summary
Metal additive manufacturing is gaining interest in industries such as tooling, which is mainly due to the possibility to manufacture complex shapes, which allow for the fabrication of intricate internal cooling channels, and at the same time to achieve fine microstructures. The EBM technology has several characteristics that make it well-suited for processing highly alloyed steels for tooling applications, such as the selective and local heating, high building temperatures, high vacuum during processing, and high building rates [12,13,14]. Within this group of materials, most manufacturing efforts using EBM have targeted hot-work tool steels [2,3,4,6]. There is a lack of investigations focusing on high carbon cold-work tool steels, and just a few reports can be found in the literature, where only one example refers to the use of AM in the production of worm-milling cutters [15,16,17]
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