(1State Key Laboratory of Materials Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China) (2Hubei Sanhuan Intelligent Technology Co., Ltd., Wuhan 430074, China)
Materials aging is an important factor influencing the properties and surface accuracy of components fabricated by selective laser sintering (SLS) technology, the underlying cause is the microstructure changes of materials. Therefore, this work emphatically studied the mechanism of polyamide-12 (PA12) aging, and the changes of crystal structure, chemical states of elements and properties of the aged powders and the corresponded components after SLS process. The results show that the XRD patterns of the aged powders appear the peaks like Brill transition, resulting in the improvement of melting temperature of the aged powder. Moreover, the sintering window of the PA12 powder recycled for three times is expanded to 3100 ℃. Xray photoelectron spectroscopy spectra demonstrates the presence of solid and melt state polycondensation, which results in higher nucleation temperatures of aged powders. Meanwhile, the crystallization delay phenomenon of components fabricated with aged powders is observed by differential scanning calorimetry. With the increase of aging level of PA12 powder, its crystallinity is generally reduced by solid state polycondensation.