Effect of baseplate temperature on sputter-generation for development of SLM in vacuum

A titanium (Ti) plate was fabricated by selective laser melting (SLM) in vacuum to investigate the preheat effect. A melting and solidification dynamics of the Ti powder on the preheated baseplate was captured by high speed video camera. As the results, when a baseplate temperature was at room temperature of 25 degrees Celsius, sputtering was occurred while the laser irradiation. On the other hand, when the baseplate temperature was heat up to 150, 200 degrees Celsius, and amount of the sputtering was reduced. In order to investigate a material structure, the fabricated sample were cut into perpendicular and parallel direction to the laser scanning direction, In order to investigate a crystal orientation, the fabricated sample were cut into perpendicular and parallel direction to the laser scanning direction. After cutting, corrosion test was carried out to observe a crystal grain, grain boundary and direction of grain growth on the cross section of the sample with Crole solution such as this containing HF (Hydrofluoric acid) and H₂NO₃(nitric acid) solution. An angle between the perpendicular line of the baseplate and a growth direction were measured for cross section of perpendicular to the laser scanning direction. From the results, the angle was 59° at the 25 degrees Celsius. When the baseplate temperature heated up to 200 degrees Celsius, the growth angle was decreased to 24 degrees. As the results, it was revealed that the growth angle of crystal grains was controlled by baseplate temperature.