Origin of stray-grain formation and epitaxy loss at substrate during laser surface remelting of single-crystal nickel-base superalloys

• The mechanism of stray-grain formation at substrate of laser-processing single-crystal superalloys was first investigated.
• The relationship between stray-grain formation and microsegregation in the substrate was first found.
• A basic precondition, the homogenized treatment of substrate, for successful single-crystal laser processing was revealed.

The stray-grain formation and epitaxy loss at the substrate during laser surface remelting of single-crystal nickel-base superalloys, which immediately lead to the break of the single-crystal growth, were investigated by means of modeling and experiments. Results indicate that the stray-grain formation and epitaxy loss at the substrate are attributed to the increased trend of the formation of equiaxed grains resulting from the composition segregation at the substrate interdendritic region. Accordingly, a solution treatment for the substrates prior to laser processing can effectively avoid the SG formation and epitaxy loss, which reveals a basic precondition, homogenized solution treatment of substrates, for successful single-crystal laser processing.

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