Influence of Porosity in LBM Layers on the Quality of Laser Deep Alloying

Abstract

Abstract Powder bed-based processes such as laser beam melting (LBM) are becoming increasingly relevant in industrial production environments. A novel approach is to use the LBM process for the targeted addition of alloy elements for the laser deep alloying process. In this two-step process, pre-deposited element layers are remelted and mixed into the base material using a high-power laser and beam modulation. However, the pre-deposition of master alloy by means of LBM may induce pores of varying intensity in the applied layers. The present work deals with the influence of such porosity in pre-deposited layers on the resulting microstructure of deep-alloyed micro-samples and thus on the quality of laser deep alloying. The goal was to investigate the suitability of the LBM process for the addition of alloy elements into the melt pool to maintain high throughput material development. For this purpose, an atomized stainless steel was applied in different layer thicknesses on an unalloyed steel. In addition, a different porosity was set in the layers. On average, only a few pores appeared in the microstructure after laser deep alloying. Instead, cracks occurred unsystematically in the microstructure. The experiments have shown that the porosity of pre-deposited layers has no influence on the formation of pores or cracks in the resulting microstructure after laser deep alloying. Thus, it was established that regarding pores in the layers, the laser deep alloying process is stable against fluctuations in the energy deposition in the LBM process.