Powder-entrapped gas, which can occur naturally in gas-atomized powder, can induce porosity in parts fabricated with powder-based metal additive manufacturing processes. This study utilized synchrotron-based x-ray computed tomography and an in situ high-speed imaging technique, dynamic x-ray radiography (DXR), to investigate the formation of powder-induced porosity using 17-4 PH stainless steel powders with a controlled size distribution and intentionally varied entrapped gas contents. While powder with a low entrapped gas content showed no net part porosity increase, the results showed a strong correlation between the porosity in the powder and the porosity in the builds made from powder with a high entrapped gas content relative to typical gas-atomized powder. A threshold value was developed to classify porosity induced by powder-entrapped gas based on pore morphology measured using computed tomography. Transfer and coalescence of pores during laser melting was observed directly with DXR.

中文翻译：

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17-4 PH 不锈钢零件激光粉末床熔合粉末气体截留及其对孔隙率影响的研究

气体雾化粉末中自然存在的粉末夹带气体会导致使用粉末基金属增材制造工艺制造的零件产生孔隙。本研究利用基于同步加速器的 X 射线计算机断层扫描和原位高速成像技术动态 X 射线射线照相 (DXR) 来研究使用 17-4 PH 不锈钢粉末和受控尺寸分布和有意改变夹带气体含量。虽然具有低截留气体含量的粉末未显示净部分孔隙率增加，但结果表明，相对于典型的气体雾化粉末，粉末中的孔隙率与由具有高截留气体含量的粉末制成的构造中的孔隙率之间存在很强的相关性。基于使用计算机断层扫描测量的孔隙形态，开发了一个阈值来对粉末夹带气体引起的孔隙度进行分类。用 DXR 直接观察到激光熔化过程中孔的转移和聚结。