Thermal behavior during selective laser melting of commercially pure titanium powder: Numerical simulation and experimental study

Abstract

A three-dimensional model was developed for studying thermal behavior during selective laser melting (SLM) of commercially pure titanium (CP Ti) powder. The effects of scan speed and laser power on SLM thermal behavior were investigated. The results showed that the average temperature of the powder bed gradually increased during the SLM process, caused by a heat accumulation effect. The maximum molten pool temperature (2248°C) and liquid lifetime (1.47ms) were obtained for a successful SLM process for a laser power of 150W and a laser scan speed of 100mm/s. The temperature gradient in the molten pool increased slightly (from 1.03×104 to 1.07×104°C/mm in the direction perpendicular to the scanning path; from 1.21×104 to 1.28×104°C/mm in the thickness direction) when the scan speed was increased from 50 to 200mm/s, but increased significantly (from 1.29×104 to 8.24×104°C/mm in the direction perpendicular to the scanning path; from 1.53×104 to 9.84×104°C/mm in the thickness direction) when the laser power was increased from 100 to 200W. The width and depth of the molten pool decreased (width from 137.1 to 93.8μm, depth from 64.2 to 38.5μm) when the scan speed was increased from 50 to 200mm/s, but increased (width from 71.2 to 141.4μm, depth from 32.7 to 67.3μm) when the laser power was increased from 100 to 200W. Experimental SLM of CP Ti powder was carried out under different laser processing conditions and the microstructure of SLM-produced parts was investigated to demonstrate the reliability of the physical model and simulation results.