Directed energy deposition of PH 13–8 Mo stainless steel: microstructure and mechanical property analysis

IF 2.9 3区 工程技术 Q2 AUTOMATION & CONTROL SYSTEMS
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Abstract

Laser metal deposition (LMD) is of the directed energy deposition (DED) process which is widely used for producing large-scale, dense, and functional parts in the field of additive manufacturing (AM). This research work investigates the microstructure and mechanical properties of PH 13–8 Mo martensitic stainless-steel parts produced via LMD. The workshop trials were conducted using an LMD system collaborated with a robotic arm to deposit single-track thin walls and horizontal blocks. The microstructural characteristics of the additively manufactured parts were analyzed using an optical microscope. The mechanical properties were evaluated through hardness measurements and uniaxial tensile tests. The influence of energy density and powder deposition density on the characteristic geometry of straight walls was also investigated. The microstructural analysis showed that the microstructure consisted of columnar dendrites that grew epitaxially from the substrate, with primary austenite cells containing intercellular ferrite and martensite laths that were roughly parallel with the retained austenite. When the energy density increased from 43 to 86 J/mm2 (a doubling of energy density), there was an increase in secondary dendritic arm spacing (SDAS) by approximately 250% in the first layer and approximately 90% in the top layer. The difference in SDAS change between the first and top layers can be attributed to the difference in cooling rates experienced by each layer during the additive manufacturing process. Increasing powder deposition density from 0.5 to 1 g/min results in a decrease in porosity from 3% to less than 1% and an increase in strength from 800 to over 1000 MPa. The hardness of the deposits was found to range from 300 to 400 HV. This variation in hardness can be attributed to differences in microstructure resulting from changes in cooling rates at different heights.

PH 13-8 Mo 不锈钢的定向能沉积:微观结构和机械性能分析
摘要 激光金属沉积(LMD)属于定向能沉积(DED)工艺,在增材制造(AM)领域被广泛用于生产大规模、高密度和功能性零件。本研究工作调查了通过 LMD 生产的 PH 13-8 Mo 马氏体不锈钢零件的微观结构和机械性能。车间试验使用 LMD 系统与机械臂协作,沉积单轨薄壁和水平块。使用光学显微镜分析了快速成型零件的微观结构特征。通过硬度测量和单轴拉伸试验评估了机械性能。此外,还研究了能量密度和粉末沉积密度对直壁几何特征的影响。微观结构分析表明,微观结构由从基体外延生长的柱状树枝状晶组成,初级奥氏体晶胞含有胞间铁素体和马氏体板条,这些板条与保留的奥氏体大致平行。当能量密度从 43 焦耳/平方毫米增加到 86 焦耳/平方毫米(能量密度增加一倍)时,第一层的次生树枝状晶臂间距(SDAS)增加了约 250%,顶层的次生树枝状晶臂间距增加了约 90%。第一层和顶层的 SDAS 变化差异可归因于各层在增材制造过程中所经历的冷却速率不同。将粉末沉积密度从 0.5 g/min 提高到 1 g/min,可使孔隙率从 3% 降低到 1%以下,强度从 800 MPa 提高到 1000 MPa 以上。沉积物的硬度范围为 300 至 400 HV。硬度的这种变化可归因于不同高度下冷却速率的变化所导致的微观结构的差异。
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来源期刊
CiteScore
5.70
自引率
17.60%
发文量
2008
审稿时长
62 days
期刊介绍: The International Journal of Advanced Manufacturing Technology bridges the gap between pure research journals and the more practical publications on advanced manufacturing and systems. It therefore provides an outstanding forum for papers covering applications-based research topics relevant to manufacturing processes, machines and process integration.
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