Laser powder bed fusion of nickel alloy 625: Experimental investigations of effects of process parameters on melt pool size and shape with spatter analysis

• Published in: International journal of machine tools & manufacture 2017-10, Vol.121, p.22-36
• Main Authors: Criales, Luis E., Arısoy, Yiğit M., Lane, Brandon, Moylan, Shawn, Donmez, Alkan, Özel, Tuğrul
• Format: Article
• Language: English
• Subjects: Additive manufacturing; Cooling rate; Coordination compounds; Gas turbine engines; Gas turbines; Heating; Jet engines; Laser fusion; Lasers; Materials selection; Melt pool; Melting; Metal powders; Nickel alloy; Nickel base alloys; Powder bed fusion; Process parameters; Selective laser melting; Spatter; Structural integrity; Studies
• ISSN: 0890-6955; 1879-2170
• DOI: 10.1016/j.ijmachtools.2017.03.004

Laser powder bed fusion (L-PBF) as an metal additive manufacturing process that can produce fully dense 3D structures with complex geometry using difficult-to-process metal powders such as nickel-based alloy 625 which is one of the choice of metal materials for fabricating components in jet engines and gas turbines due to its high strength at elevated temperatures. L-PBF process parameters and scan strategy affect the resultant built quality and structural integrity. This study presents experimental investigations of the effects of process parameters and scan strategy on the relative density, melt pool size and shape. Fabricated test coupons were analyzed with two objectives in mind: i) to determine how close each coupon was to fully dense and ii) to determine melt pool dimensions (width and depth) and shape for each coupon. The identification and definition of a dynamic melt pool has been performed, a condition which indicates that melt pool geometry is constantly changing as the laser scans and moves along a single track. In order to gain in-depth understanding of the laser fusion processing of powder material, an in-situ thermal camera video recording is performed and analyzed for meltpool size, spattering particles, and heating and cooling rates during processing of powder material nickel alloy 625. The results reveal in-depth process information that can be used for further validation of modeling studies and adopted for the industrial practice. •Presented investigations on laser powder bed fusion of nickel alloy 625 powder material.•Dynamic melt pool is identified where melt pool size is constantly changing along a single track.•Melt pool is affected by increasing energy density as it gets wider, deeper, and more asymmetrical.•Significant powder material spatter is observed using thermal camera video monitoring.•Heating rates between 600°C/ms and 1000°C/ms, and cooling rates of 150°C/ms are measured.