Formation of scanning tracks during Selective Laser Melting (SLM) of pure tungsten powder: Morphology, geometric features and forming mechanisms

摘要

Due to the high melting point and high heat conductivity, selective laser melting (SLM) of tungsten is still challenging. To have a better understanding of SLM tungsten parts, the effects of processing parameters such as laser power and scanning speed on scanning tracks formation of pure tungsten powder were investigated. As linear energy increased with increasing laser power and decreasing scanning speed, the height and contact angle of scanning tracks gradually reduced, while the width and penetration depth increased. Owing to the good wetting and spreading, the flow front of scanning tracks gradually became smooth and stable with the increased linear energy. However, the transverse cracks induced by large temperature gradient and high cooling rate appeared on the surface of the scanning tracks at linear energy of more than 1.75 J/mm. A maximum temperature of 4630.27 degrees C and high cooling rate of 8.6 x 10(6) degrees C/s were obtained during SLM process of tungsten powder when the linear energy was 1.75 J/mm. This work provides scientific guidance for SLM-processed tungsten parts.