Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7951842 | Journal of Materials Science & Technology | 2018 | 9 Pages |
Abstract
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 â30â¯Â°C and +210â¯Â°C 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 Tsubâ¯â¤â¯+90â¯Â°C. When the substrate preset temperature Tsub is below +90â¯Â°C, 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.
Related Topics
Physical Sciences and Engineering
Materials Science
Materials Chemistry
Authors
Zhaoyang Liu, Zi Wang,