Effect of defocus amount of rotational beam coupled laser on the grooving characteristics of nickel-based superalloys

Nickel-based superalloys are widely used in aviation, aerospace, energy, petrochemical and other industrial fields due to their excellent high temperature strength, oxidation and corrosion resistance, excellent creep and fatigue resistance. However, there are many problems in the traditional processing methods, such as tool wear, thermal/mechanical damage of materials and so on. These problems limit the processing ability of micro structures and complex surfaces, making it difficult to process nickel-based superalloy components with high quality. Laser processing has the advantages of high precision, non-contact and green, which has become an effective means of nickel-based superalloy surface processing. In this paper, a new process of rotational multi-beam coupled nanosecond laser processing was used to study the groove cutting of nickel-based superalloy with variable defocus amount. The morphology and structure of the groove were observed and analyzed by laser confocal microscope and scanning electron microscope. The results show that the groove width is the smallest and the groove depth is larger when the defocus amount is -1.0mm, and the laser energy density is larger when the defocus amount is close to -1.0mm, and a relatively high adhesion layer is formed between the groove edge and the unmachined surface. By analyzing the groove straightness under different defocus amounts, the groove straightness first decreases and then increases, and the straightness is the smallest at -1.0mm, indicating that -1.0mm defocus position is a relatively suitable processing position. The research work can provide process guidance for the laser processing application of nickel-based superalloys.