Abstract

Single track and multi-layers of medium-carbon steel (AISI H13) powders were additively deposited on gray cast iron using a directed energy deposition (DED) technique. Multi-scale microstructure characterization using a scanning electron microscopy, an electron probe micro-analyzer and a scanning transmission electron microscopy, and the thermal analysis using finite element method were performed to understand the mechanism for the micro-crack formation, which was found at the single, double and triple layers of medium-carbon steel powders, except for the single track, deposited on a cast iron substrate. The crack formation mechanism was thoroughly investigated by combining the layer-by-layer chemistry variations and the resulting microstructural evolution upon exposure to thermal cycles during the DED process. It was concluded that micro-cracking was accompanied by the initiation of the local graphitization and the formation of plate martensite in the vicinity, which seemed to be kinetically facilitated by an indirect exposure to multiple heating–cooling thermal cycles, not by a direct exposure to a melting-cooling (solidification) cycle.

Graphic Abstract

中文翻译：

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定向能量沉积法在灰铸铁上附加沉积的中碳钢层中的微裂纹

摘要

使用定向能量沉积（DED）技术将单轨和多层中碳钢（AISI H13）粉末添加到灰铸铁上。使用扫描电子显微镜，电子探针显微分析仪和扫描透射电子显微镜进行多尺度微观结构表征，并使用有限元方法进行热分析，以了解微裂纹形成的机理。单层，双层和三层中碳钢粉（单道除外）沉积在铸铁基材上。通过结合逐层化学变化和在DED过程中暴露于热循环时产生的微观结构演变，对裂纹形成机理进行了彻底研究。

图形摘要