Grain size evolution under different cooling rate in laser additive manufacturing of superalloy

• Published in: Optics and laser technology 2019-11, Vol.119, p.105662, Article 105662
• Main Authors: Shao, Jiayun, Yu, Gang, He, Xiuli, Li, Shaoxia, Chen, Ru, Zhao, Yao
• Format: Article
• Language: English
• Subjects: Additive manufacturing; Computer simulation; Cooling; Cooling rate; Grain size; Laser additive manufacturing; Laser cooling; Laser deposition; Lasers; Marangoni convection; Microstructure; Optimization; Phase transitions; Process parameters; Scanning; Solidification; Superalloy; Superalloys; Three dimensional models
• ISSN: 0030-3992; 1879-2545
• DOI: 10.1016/j.optlastec.2019.105662

•Relationship between grain size, cooling rate and processing parameters had been studied.•Arbitrary Lagrange-Euler method (ALE) was used to describe the free surface deformation.•Solidification parameters especially cooling rate (G × R) were simulated to illustrate the underlying mechanisms.•Grain size decreased with the increase of scanning speed due to the increase of cooling rate.•A specific G-R map for the investigated Ni45 alloy in the region of equiaxed dendrite growth was obtained. The processing parameters in laser additive manufacturing have a crucial impact on solidification microstructure especially grain size, thus influencing the properties of the final products. In this paper, experiments were conducted to investigate the effects of processing parameters including scanning speed, laser power and powder feeding rate on grain size of the solidified track during laser metal deposition. A three-dimensional model considering heat transfer, phase change and Marangoni convection flow had also been developed to simulate the solidification parameters especially cooling rate (G × R) to illustrate the underlying mechanisms. The experimental and simulated results indicated that cooling rate increased and grain size decreased from 8.7 μm to 4.7 μm with the increase of scanning speed from 2 mm/s to 10 mm/s. Contrarily, cooling rate decreased and grain size increased with the increase of laser power and powder feeding rate. The numerical and experimental results provide the additive manufacturing process with the potential of microstructure control and performance optimization.