Research on a new high-quality and high-efficiency SLM forming method based on interlayer strategy

¹ Mechanical Industry Key Laboratory of Heavy Machine Tool Digital Design and Testing, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, China
² Beijing Key Laboratory of Advanced Manufacturing Technology, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, China

Abstract

To ensure the forming quality of SLM and to improve the forming efficiency of SLM, this paper investigates the forming effect of Ti6Al4V specimens formed by SLM based on an interlayer strategy. The conditions for improving the relative density of the specimens are high laser power, small point distance, long exposure time and long hatch spacing. High laser power provides sufficient laser energy density in the formation of thicker powder layers, reduced point distance ensures wetting behavior of the melt pool, longer exposure time provides the time required to fully melt the powder and increased hatch distance facilitates dispersion of the laser energy density. Process parameters have a strong influence on the relative density of SLM formed specimens, and by adjusting the process the highest density of 99.99% can be achieved. The microstructure of the specimens consisted mainly of acicular martensite α′ and columnar β grains due to the effects of repeated thermal cycling. Due to the presence of martensite α′, the tensile and yield strengths of the specimens are increased, but the elongation of the specimens is reduced.