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.

中文翻译：

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热处理对定向能量沉积沉积的AISI M4层的影响

当前，高速钢（HSS）粉末通过直接能量沉积（DED）局部沉积在金属表面上的硬面工具钢上。尽管HSS粉末提高了金属表面的硬度和耐磨性，但由于其高碳含量，它使工具钢变脆。另外，随着时间的流逝，钢可能会破裂。这项研究的重点是通过应用后热处理来提高钢的韧性。为了通过DED制造均匀沉积的层，将M4粉末沉积到预热的基材（AISI D2）上。另外，制备了四个后热处理样品，并比较了它们的机械性能。进行了夏比冲击和硬度测试，以评估D2模具所需的耐久性。所沉积的M4粉末具有高硬度但相对较低的冲击韧性。在激光熔化过程中，M4和D2之间形成了稳定的结合，没有任何裂纹或分层。最初的M4沉积层的硬度为63 HRC，取决于后热处理的效果，其硬度变为54-63 HRC。而且，后热处理工艺通过改变其微结构而提高了M4沉积层的冲击韧性。