Product Code: ICAL06_1204

Absorption Coefficient Characterization in Ti-6Al-4V Laser Additive Manufacturing
Authors:
Anil Chaudhary, Applied Optimization, Inc.; Dayton OH USA
Matt Keller, Applied Optimization, Inc.; Dayton OH USA
Shawn Kelly, Laser Processing Division, ARL; State College, PA PA USA
Steven Medeiros, Wright Patterson AFB; Dayton OH USA
Presented at ICALEO 2006

In order to accurately model the laser deposition of Ti-6Al-4V aerospace components, the interaction of the laser and metal powder feedstock has been investigated. One of the key modeling parameters, the absorption coefficient of the material, is often unknown for material in powder form. It has been shown that the absorption coefficient of powdered material is often higher than solid material due to trapping and re-reflection of the laser energy within the powder bed. The current work focuses on determining the absorption coefficient of spherical Ti-6Al-4V powder irradiated using a high energy CO2 laser. Machined Ti-6Al-4V cylindrical samples with a recessed pocket were designed to hold a known mass of powder. The specimens are fitted within a protective insulation to capture and retain the incident laser energy. Knowing the equilibrium temperature as well as the transient response from thermocouple data at three locations, the laser's absorbed energy can be found. Each sample, though similar, receives a different irradiation time. Combining the results of multiple samples, values of absorption coefficients can be determined as a function of irradiation time. The absorption coefficients of the powder feedstock are on average, significantly greater than the absorption coefficient of a solid (machined) surface.