Abstract

As a novel manufacturing technology, additive manufacturing (AM) has many advantages such as energy saving, reduced material waste, faster design-to-build time, design optimization, reduction in manufacturing steps, and product customization compared to conventional manufacturing processes. Heat treatment is widely used to improve the properties of conventional manufactured steel parts. The response of additively manufactured steel parts to heat treatment may be different from conventionally manufactured steel parts due to variations in the as-deposited alloy microstructure. An understanding of heat treatment processes for additively manufactured steel parts is necessary to develop their heat treatment process parameters. In the present work, 20MnCr5 steel was selected to investigate the carburizing heat treatment of additively manufactured parts. These parts were fabricated by selective laser melting (SLM) for the carburizing study. It was found that the AM parts fabricated by the SLM process show the microstructure of tempered martensite, while the microstructure of as-received wrought part is ferrite and pearlite. It was also experimentally found that the SLM process decarburizes the entire SLM part. Before carburizing, a normalization process was conducted on both SLM and wrought 20MnCr5 parts to reduce the effect of the pre-carburizing microstructure. The objective of this project is to determine the carburizing performance of additively manufactured steel parts. The results for the SLM parts in terms of carbon concentration and microhardness profiles are compared with the results for the wrought steel. It was found that the carburized SLM part in the present work has higher carbon concentration near the surface, deeper case depth, and higher total carbon flux than the carburized wrought part.

中文翻译：

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选择性激光熔炼20MnCr5钢的渗碳热处理

摘要

与传统制造工艺相比，增材制造（AM）作为一种新颖的制造技术，具有许多优势，例如节能，减少材料浪费，缩短设计到制造时间，优化设计，减少制造步骤以及定制产品。热处理被广泛用于改善常规钢制零件的性能。由于沉积合金微结构的变化，增材制造的钢部件对热处理的响应可能与常规制造的钢部件不同。必须了解增材制造的钢零件的热处理工艺，以开发其热处理工艺参数。在目前的工作中，选择20MnCr5钢来研究增材制造零件的渗碳热处理。这些零件是通过选择性激光熔化（SLM）制造的，用于渗碳研究。结果表明，采用SLM工艺制造的AM零件具有回火马氏体的显微组织，变形后零件的显微组织为铁素体和珠光体。还通过实验发现，SLM工艺使整个SLM零件脱碳。在渗碳之前，对SLM和变形的20MnCr5零件都进行了正火处理，以减少预渗碳组织的影响。该项目的目的是确定增材制造钢零件的渗碳性能。将SLM零件在碳浓度和显微硬度方面的结果与锻钢的结果进行了比较。