Influence of Support Structures on the Microstructure and Mechanical Properties of Case Hardening Steel in Laser Powder Bed Fusion
Influence of Support Structures on the Microstructure and Mechanical Properties of Case Hardening Steel in Laser Powder Bed Fusion
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DOI：
10.2139/ssrn.3724368
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发表时间：
2020-11
期刊：
影响因子：
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通讯作者：
M. Schmitt;Maximilian Bösele;G. Schlick;G. Reinhart
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文献类型：
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作者：
M. Schmitt;Maximilian Bösele;G. Schlick;G. Reinhart
增材制造，特别是激光粉末床熔融（LPBF），使制造复杂和轻质零件成为可能。LPBF是一种具有高度几何自由度的技术，但存在生产限制，例如，关于悬垂。尽管有这些限制，但生产这些部件的一种策略是使用支撑结构。在LPBF加工之后，在一般后处理（例如，制造功能表面或热处理）结束之前，通过手工或机械加工去除支撑结构。然而，在LPBF过程中，支撑结构会根据零件的几何形状（无支撑结构与使用支撑结构）改变局部工艺条件。这种影响主要是由于支撑结构相对于致密部件材料的散热特性发生了变化。在这篇论文中，研究了支撑结构对16MnCr5淬火钢的微观组织和力学性能的影响。表面硬化钢用于齿轮和小齿轮，广泛应用于航空航天工业，例如直升机或无人机（无人机）的发动机齿轮箱。可见，应用的支撑结构高度对微观结构的影响很大。机械性能是通过缺口杆冲击试验确定的，表明随着支撑结构高度的增加，在建成状态下韧性增加。这与显微组织中铁素体含量的增加相一致。随后的热处理（去应力退火和淬火）对力学性能的影响也进行了研究。此外，基于上述结果，提出并描述了支撑结构影响和LPBF中发生的原位热处理的广义操作原理。
Additive manufacturing, especially laser powder bed fusion (LPBF), enables the manufacturing of complex and lightweight parts. LPBF is a technology with high geometric degrees of freedom, but there are production restrictions, e.g., with regard to overhangs. One strategy to produce these components despite the restrictions is the use of support structures. After the LPBF process the support structures are removed by hand or through machining before general post-processing, e.g., manufacturing of functional surfaces or heat-treatments are concluded. However, support structures change the local process conditions during LPBF depending on the parts geometry (no support structures vs. use of support structures). The influence is mainly caused by the changed heat dissipation of the support structures compared to dense part material. In this contribution, the influence of support structures on the resulting microstructure and the mechanical properties are determined for the case hardening steel 16MnCr5. Case hardening steels are used for gearings and pinions for wide applications in the aerospace industry, e.g., engine gear boxes for helicopters or UAVs (unmanned aerial vehicles). It can be seen that the height of the applied support structures has great influence on the microstructure. Mechanical properties are determined through notched bar impact testing showing an increase in toughness in the as-built state with increasing support structure height. The findings correspond with the increasing content of ferrite seen in the microstructure. The effect of subsequent heat treatments (stress relief annealing and case hardening) on the mechanical properties is also investigated. Furthermore, generalized operating principles for the influence of support structures and the occurring insitu heat treatment in LPBF are presented and described based on the results shown.