Purpose

Characteristics of the metal powder are a key factor in the success of powder bed fusion (PBF) additive manufacturing. Powders for PBF from different manufacturers may have a different particle size and/or bulk packing and flow behavior. Powder properties change as the powder is reused for multiple builds. This study seeks to measure the variability of commercial 17-4 PH stainless steel powders to determine the effect of powder variability on part density and demonstrate characterization methods that ensure part quality.

Design/methodology/approach

Commercial atomized metal powders from four different vendors were produced with two different atomizing gases (N2 and argon). Powder was characterized in both new and extensively reused conditions. All powders were characterized for flow and packing behavior, particle size and internal porosity. Coupons were manufactured using the laser PBF process with optimized scan strategy and exposure parameters. The quality of fabricated parts was measured using bulk density measurement.

Findings

Despite differences in powder flowability and particle size, fully dense parts (>99 per cent) were produced using all powders, except one. Residual porosity in these parts appeared to result from gas trapped in the powder particles. The powder with extensive reuse (400+ h in machine fabrication environment) exhibited reduced flowability and increased fraction of fine particles, but still produced full density parts.

Originality/value

This study demonstrates that full density parts can be fabricated using powders with a range of flowability and packing behavior. This suggests that a single flowability measurement may be sufficient for quality assurance in a production environment.

中文翻译：

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17-4 PH不锈钢粉末床熔合的粉末特性和零件密度

目的

金属粉末的特性是粉末床熔融（PBF）增材制造成功的关键因素。来自不同制造商的PBF粉末可能具有不同的粒度和/或散装和流动行为。随着粉末重复用于多种构造，粉末性能也会发生变化。这项研究旨在测量商用17-4 PH不锈钢粉末的变异性，以确定粉末变异性对零件密度的影响，并演示确保零件质量的表征方法。

设计/方法/方法

使用两种不同的雾化气体（N2和氩气）生产了来自四个不同供应商的商业雾化金属粉末。在新的和广泛使用的条件下对粉末进行了表征。所有粉末均具有流动性和堆积特性，粒度和内部孔隙率的特征。优惠券使用激光PBF工艺制造，具有优化的扫描策略和曝光参数。使用堆积密度测量法测量制造零件的质量。

发现

尽管粉末的流动性和颗粒度有所不同，但除一种粉末外，所有粉末均能生产出完全致密的零件（> 99％）。这些部分中的残余孔隙似乎是由粉末颗粒中捕获的气体引起的。具有广泛重复使用性的粉末（在机器制造环境中为400+ h）显示出降低的流动性和增加的细颗粒分数，但仍生产出全密度零件。

创意/价值

这项研究表明，可以使用具有一定范围的流动性和堆积行为的粉末来制造全密度零件。这表明，单个流动性测量可能足以保证生产环境中的质量。