Botero Carlos Alberto, Şelte Aydın, Ramsperger Markus, Maistro Giulio, Koptyug Andrey, Bäckström Mikael, Sjöström William, Rännar Lars-Erik
Department of Quality Technology and Mechanical Engineering, Sports Tech Research Centre, Mid Sweden University, Kungskapensväg 8, SE-83125 Östersund, Sweden.
Uddeholms AB, Uvedsvägen, SE-683 85 Hagfors, Sweden.
Materials (Basel). 2021 May 31;14(11):2963. doi: 10.3390/ma14112963.
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.
在本研究中，通过电子束熔炼（EBM）技术制造了一种高合金化冷作工具钢，即乌德霍姆瓦纳迪斯4特级钢。对相应的材料微观结构、碳化物析出行为以及热处理后的微观结构变化进行了表征，并研究了关键力学性能。在铸态条件下，微观结构由非常细小的初生富钼和富钒碳化物的不连续网络组成，这些碳化物分散在自回火马氏体基体中，同时还有约15%的残余奥氏体。调整后的热处理工艺能够通过消除富钼碳化物和析出细小且尺寸不同的富钒碳化物来优化微观结构，同时将残余奥氏体含量降低至2%以下。电子束熔炼制造材料的硬度响应、抗压强度和耐磨性能与其采用传统粉末冶金路线制造的热等静压锻造对应材料相似或更优。在电子束熔炼制造的材料中，冲击韧性达到了16 - 17焦耳。采用热等静压（HIP）以进一步提高延展性，并研究其对材料微观结构和性能的影响。经过优化工艺的热等静压处理后，延展性提高到了20焦耳以上。
