Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Evaluation of "micro-cladding" parameters in face of thermal effects reduction for top-hat lasers
Submission Author:
Joares Reis , SP
Co-Authors:
Joares Reis, Paulo Dyer, Silvelene Silva, Helder Vicente, Andersan dos Santos Paula, Danilo Gonçalves, Naiara Vieira Le Sénéchal, Getúlio Vasconcelos
Presenter: Paulo Dyer
doi://10.26678/ABCM.COBEM2023.COB2023-2231
Abstract
Coating or additive manufacture by laser cladding procedures has a wide range of industrial and technological applications; in face of versatility and good anchorage between the composite layers. Where the metallurgical bond is performed by the high temperatures of laser beam. However, these advantages may be compromise or significantly modify the microstructure of coated metallic alloy, according to laser beam profiling. Since, the types of laser beams cross sections are segmented into Gaussian and top-hat. Whereas in the Gaussian the energy decreases symmetrically from the center of the beam; top-hat or flap-top beams maintain a constant irradiance across the cross section, providing, in theory, a constant energy from the target. Therefore, the power required for Gaussian must be higher than top-hat beams; since the irradiation required for material fusion will propagate gradually in the vicinity of the beam center. Thus, it is expected a higher material diffusion below the cladding with Gaussian beams, considering same top-hat laser power. Nevertheless, as observed in this present investigation, in practice top-hat lasers are imbued of small energy peaks in the center region; producing an extra melt area (Ap), under the substrate melting area (Am). In this context, this paper aimed a coating cross-section investigation, demonstrating this melting regions occurrence (Ap); due to peak energy from top-hat laser. Furthermore, this study aimed to trace a correlation between the efficiency (E) associated to laser power (P), as well scan speed (vs) and powder feeding rate (µ) in order to establish parameters to define a concept of "micro-cladding" or an Ap equivalent to an Am for a given cladding area Ac; generating clad conditions, without high temperatures effect. For this, H13 tool steel powder was used as a coating on 4340 steel substrates. Laser cladding was performed with IPG top-hat laser with a maximum P of 1500 W and beam diameter or “spot” (bd) of 6 mm, coupled to Yaskawa CP25 robotic arm producing a single line track cladding, with E and vs variation. Then, samples were characterized by optical microscopy determining dilution (D), “HAZ angle” (α’) and clad angle (α) parameters. As result, were determined that a “E” of 86.6%, vs = 15 mm/s and µ = 6 g/min are able to produce a satisfactory micro-cladding with D ≈ 31% and α of 112.70°. Concluding that top-hat lasers are capable to optimize the clad parameters; with this, a low substrate microstructure interference by heat, were produced.
Keywords
Micro-cladding, top-hat laser beam, robotic arm, low power cladding processing
