Lerda Serena, Marchese Giulio, Bassini Emilio, Lombardi Mariangela, Ugues Daniele, Fino Paolo, Biamino Sara
DISAT-Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy.
IAM@PoliTo-Interdepartmental Center of Integrated Additive Manufacturing, Politecnico di Torino, Corso Castelfidardo 51, 10129 Torino, Italy.
Materials (Basel). 2024 Sep 14;17(18):4532. doi: 10.3390/ma17184532.
This paper deals with the development and characterization of an Inconel 625 (IN625) reinforced with 2 wt.% of sub-micrometrical TiC particles produced by the laser powder bed fusion (LPBF) process. IN625 and IN625 2 wt.% TiC microstructural evolution was evaluated in the as-built, solution-annealed (2 h at 1150 °C), and prolonged heat-treated (2 h at 1150 °C + 100 h at 1000 °C) conditions. The IN625 and IN625 + TiC samples were successfully produced with low residual porosity (<0.15%). In the as-built conditions, both materials developed mainly columnar grains elongated to the building direction with melt pools, fine dendric structures, and small fractions of recrystallized grains. Some TiC segregations were observed in the composite, preferentially located at the melt pool boundaries. The heat treatments led to a different microstructural evolution between the base alloy and the composite. After solution annealing, the IN625 alloy was subjected to full recrystallization with a drastic reduction in hardness. Afterward, the prolonged thermal exposures for 100 h at 1000 °C provoked the formation of carbides, increasing the hardness. On the contrary, the composite retained the as-built microstructure with columnar grains in the solution-annealed and prolonged heat-treated conditions, revealing a limited formation and growth of carbides, thus resulting in a reduced hardness variation. The addition of TiC inside the IN625 enhanced the microstructural stability of the composite, preventing the recrystallization and the growth of phases occurring under prolonged thermal exposures. The current study therefore reported the effect of TiC particles on the microstructural stabilization of LPBFed IN625, with a peculiar focus on the prolonged thermal exposure at 1000 °C.
本文研究了通过激光粉末床熔融（LPBF）工艺制备的、含有2 wt.%亚微米级TiC颗粒增强的Inconel 625（IN625）合金的开发与表征。对IN625以及含有2 wt.% TiC的IN625在增材制造态、固溶退火（1150 °C下保温2小时）和长时间热处理（1150 °C下保温2小时 + 1000 °C下保温100小时）条件下的微观结构演变进行了评估。成功制备出了残余孔隙率低（<0.15%）的IN625和IN625 + TiC样品。在增材制造态条件下，两种材料主要形成了沿构建方向拉长的柱状晶，伴有熔池、细小的树枝状组织以及少量的再结晶晶粒。在复合材料中观察到了一些TiC偏析，优先位于熔池边界处。热处理导致基体合金和复合材料的微观结构演变不同。固溶退火后，IN625合金发生完全再结晶，硬度急剧降低。随后，在1000 °C下进行100小时的长时间热暴露促使碳化物形成，硬度增加。相反，在固溶退火和长时间热处理条件下，复合材料保留了增材制造态的柱状晶微观结构，显示出有限的碳化物形成和生长，因此硬度变化减小。在IN625中添加TiC增强了复合材料微观结构的稳定性，防止了长时间热暴露下发生的再结晶和相生长。因此，本研究报告了TiC颗粒对激光粉末床熔融制备的IN625微观结构稳定性的影响，特别关注了在1000 °C下的长时间热暴露。
