Regulation Mechanism of Femtosecond Laser-Etched Substrate on Laser Cladding Layer Morphology

The control of cladding layer morphology is crucial in laser cladding technology. However, traditional process parameter-based regulation suffers from parameter coupling issues, and previous nanosecond laser pretreatment is prone to causing uneven substrate morphology due to significant thermal effects. This study proposes a novel substrate pretreatment method using femtosecond laser etching, employing 45 steel as the substrate and Ni45 powder as the cladding material to investigate its regulatory effect on cladding layer morphology. The results show that femtosecond laser etching enables a good linear correlation between substrate roughness and laser power, forming uniform grid-like microgrooves without the spherical remelted structures observed in nanosecond laser treatment, thus achieving superior regulatory stability. With the increase in substrate roughness, the contact angle and dilution rate of the cladding layer decrease, while the cladding height and width increase, with the optimal cladding quality obtained in the roughness range of 4~7 μm. This study reveals the intrinsic mechanism by which femtosecond laser regulates molten pool behavior through mechanical anchoring and groove guiding effects, providing a more stable technical pathway for the preparation of high-quality cladding coatings.