Consolidation characteristics of ferrous-based metal powder in additive manufacturing

Selective Laser Sintering/Selective Laser Melting (SLS/SLM) is one of the most promising additive manufacturing (AM) techniques that are widely accepted by the industrial community. This is due to its high flexibility in processing different types of material under various conditions. However, the capability of the end product to have a desirable quality comparable to traditional processing techniques is still not achievable. Consolidation characteristics and the influence of processing parameters are important in determining the SLS/SLM part quality. In this paper, the consolidation process of ferrous-based metal powder is examined by monitoring the real-time consolidation process. A high-speed camera was utilized with telescopic lenses in order to monitor the interaction of laser and material within the powder fusion zone (PFZ). Based on the study, the line consolidation can be classified into five different consolidation types. The line consolidation characteristics were analyzed according to the line consolidation width, PFZ, consolidated agglomerate diameter and metal particle splattering behavior. The influence of laser power and scan speed on these characteristics was analyzed. It was also found that the line consolidation width, PFZ, consolidated agglomerate diameter and splattering were increasing with the increase of laser power. In contrast, with the increase of scan speed the result was vice versa. These phenomena can be explained with respect to the heat transfer behavior that took place during the interaction between the laser beam, metal powder and substrate surface. The consolidation mechanism that occurred during consolidation is also reported.