Defect-based analysis of the laser powder bed fusion process using X-ray data

Abstract

Due to high production costs and a limited reproducibility of quality, the high potential of laser powder bed fusion (LPBF) has not been fully exploited yet. In fact, internal defects can have a detrimental effect on the fatigue behaviour and cause final component failure. Therefore, process-induced defects must be localized and evaluated at a higher level of detail. The present study deals with the correlation amongst pores and LPBF process parameters in AlSi10Mg components. Computed tomography (CT) allows an extensive examination of internal defects. Within this work, a total number of 2,939,830 pores detected in 96 cylindrical samples were analysed using CT. The formation of pores can be adjusted by varying the modified volume energy density, for example, by using various laser scanning speeds. Furthermore, the effect of powder preparation scan strategies (pre-heating and pre-sintering) on the formation of different pore types as well as the general reproducibility was examined. For instance, the shielding gas flow, contaminated protective windows of the lasers as well as prior powder preparation influence the formation of pores. Using prior laser powder preparation reduced the total number of pores at high scanning speeds up to 45%. When the scanning speed is increased, the number of spherical pores decreases and large and irregularly shaped pores appear. Interestingly, only the pre-heating process resulted in a reduced formation of spherical pores at low scanning speeds (1000 mm/s).