Laser sintering (LS) is widely used to produce functional polymeric parts; however, the resulting parts are often limited by their porous structure, and performance of the part may be strongly anisotropic. Relating the structural features of parts to build process conditions or powder feedstock has been explored previously. In contrast, little is known regarding how the unique internal structures of LS parts evolve and relate to their performance later in their life cycle, for example, after use in a real-world operating environment. Here, a tightly controlled LS build process and measurement campaign by standard X-ray computed tomography (XCT), supported by high-resolution synchrotron XCT, was used to benchmark the internal microstructure (e.g. porosity) as a function of four different build orientations in printed polyamide-12 (PA-12) parts. The initial performance of the parts after printing was characterized by tensile testing and dynamic mechanical analysis (DMA). Arrays of PA-12 parts in different build orientations were exposed to steam (under pressure) and air across multiple temperature and time points for the purposes of accelerated aging through oxidative and hydrolytic breakdown. Exposing parts to steam dramatically altered the internal microstructure and functional properties such as the glass transition temperature, tensile properties, and damping behavior. Notably, post-aging XCT revealed large microstructural changes after only 40 h of steam treatment relative to the as-printed specimens. Furthermore, pore reorganization and changes in crystallinity occurred regardless of whether the steam temperature was aggressive enough to induce a significant loss in mechanical properties. The build orientation dependence on the aging rate was minimal with the relative trend in performance persisting across most metrics among the different orientations even after aging.

激光烧结（LS）被广泛用于生产功能性聚合物零件；然而，所得零件经常受到其多孔结构的限制，并且零件的性能可能强烈各向异性。先前已经探索了与零件的结构特征相关以建立工艺条件或粉末原料的方法。相比之下，关于LS零件独特的内部结构如何演变以及在生命周期后期（例如，在实际操作环境中使用后）与它们的性能相关的了解甚少。在这里，由高分辨率X射线同步层析XCT支持的，由标准X射线计算机断层扫描（XCT）严格控制的LS生成过程和测量活动，用于对内部微观结构（例如孔隙度）进行基准测试，以作为四个不同生成方向的函数。印刷的聚酰胺12（PA-12）零件。印刷后零件的初始性能通过拉伸测试和动态力学分析（DMA）进行表征。将不同构造方向的PA-12零件阵列在多个温度和时间点暴露于蒸汽（在压力下）和空气中，以通过氧化和水解分解加速老化。将零件暴露于蒸汽中会极大地改变内部微观结构和功能特性，例如玻璃化转变温度，拉伸特性和阻尼行为。值得注意的是，相对于印刷后的样品，XCT老化后仅经过40 h的蒸汽处理就显示出较大的微观结构变化。此外，不管蒸汽温度是否足够高到足以引起机械性能的显着降低，都会发生孔隙重组和结晶度变化。构造方向对老化率的依赖性极小，即使在老化后，性能的相对趋势在大多数方向之间仍在大多数指标中持续存在。