Abstract
The variation in hardness and tensile properties of Ni-based single crystal (SX) superalloy DD6 during laser metal deposition processing has been investigated, and the effects of laser scanning velocity and post heat-treatment on the evolution of microstructure and its interaction with mechanical properties of deposited region were determined. It is found that the microstructure of as-deposited Ni-based single crystal superalloy mainly consists of columnar dendrite epitaxially growing from the substrate. The fine γ′ phase microstructure and dense γ/γ′ phase interfaces contribute more to the microstructural evolution and mechanical properties of deposited part formed by laser metal deposition. Furthermore, the heat treatment reduces the mechanical properties of deposited sample due to the introducing of stray grains that destroys the original single crystallinity. The mechanism unraveled here could shed light on the reliability evaluation and parameter selection of the laser metal deposition technique and other directed energy deposition technology.
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