Melt-pool motion, temperature variation and dendritic morphology of Inconel 718 during pulsed- and continuous-wave laser additive manufacturing: A comparative study

Publication date: 5 April 2017
Source:Materials & Design, Volume 119
Author(s): Simeng Li, Hui Xiao, Keyang Liu, Wenjia Xiao, Yanqin Li, Xu Han, Jyoti Mazumder, Lijun Song
Pulsed-wave laser additive manufacturing offers a number of advantages, such as a lower heat accumulation, a higher cooling rate, finer microstructures and improved mechanical properties over continuous-wave laser additive manufacturing. However, how pulsed laser acts on the melt pool motion, thermal field and hence microstructure is not clear. In this work, a three-dimensional transport model utilizing the level set method is developed to simulate the transient melt pool motion, heat/mass transfer and fluid flow for pulsed-wave laser additive manufacturing. A boundary restriction on the fluid velocity along the liquid/gas interface is employed to confine the liquid flow within the melt pool. The simulated melt pool geometry and temperature are compared with experimental measurements. Moreover, melt pool geometry/motion, temperature variation, and their influence on the microstructure of fabricated samples using both pulsed- and continuous-wave lasers are analyzed. It is found that pulsed-wave laser additive manufacturing features a rounder shaped melt pool, a periodically heartbeat-like motion of the melt pool and a doubled cooling rate. The higher tilt angle of the solidification front results in a dendrite growth direction more tilted to the laser scanning direction and the higher cooling rate results in finer columnar dendrites.

Graphical abstract

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