Effect of substrate preset temperature on crystal growth and microstructure formation in laser powder deposition of single-crystal superalloy

作     者：Zhaoyang Liu Zi Wang 无

作者机构：College of Innovation and EntrepreneurshipSouthern University of Science and Technology Shenzhen Key Laboratory for Additive Manufacturing of High Performance MaterialsSouthern University of Science and Technology State Key Laboratory of Powder MetallurgyCentral South University 

出 版 物：《Journal of Materials Science & Technology》 (材料科学技术（英文版）)

年 卷 期：2018年第34卷第11期

页      面：2116-2124页

核心收录：

学科分类：08[工学] 0817[工学-化学工程与技术] 0806[工学-冶金工程] 0805[工学-材料科学与工程（可授工学、理学学位）] 080502[工学-材料学] 0703[理学-化学] 0802[工学-机械工程] 0801[工学-力学（可授工学、理学学位）] 0702[理学-物理学] 

基　　金：supported by the Shenzhen Science and Technology Innovation Commission under project No. JCYJ20170817111811303 

主　　题：Single-crystal superalloy Crystal growth Laser powder deposition 

摘      要：A successful repair of single-crystal components needs to avoid the stray grain formation and achieves continuous epitaxial growth of columnar dendrites in the repaired zone. In this study, the effect of substrate preset temperature on crystal growth and microstructure formation in laser powder deposition of single-crystal superalloy was studied through an improved mathematical model and corresponding experimental approaches. The results indicated that the variation of substrate preset temperature between-30℃ and ＋210℃ changes the molten pool morphology little, but obviously affects the columnar-to-equiaxed transition conditions. The preheating of substrate facilitates the stray grain formation and enlarges the primary columnar dendrite arm spacing, while the situation for precooling of substrate is opposite. Under the specific processing conditions, the critical condition for continuous epitaxial growth is that the substrate preset temperature Tsub≤ ＋90℃. When the substrate preset temperature Tsubis below ＋90℃, the height ratio of melting depth to total height of the molten pool is larger than that of stray grain, ensuring that stray grains can be completely remelted and the continuous columnar dendrites during the multi-layer laser powder deposition process on（001） surface of single-crystal substrate can be achieved.