Single-channel multilayer forming mechanism of laser cladding Fe60 process under different laser heat source working mode

Abstract

Continuous wave (CW) and pulsed wave (PW) are the two principal modes of working to control the laser heat source. Different laser heat source working modes have an essential impact on the rapid cooling and heating temperature change rate during the cladding, which directly determines the cladding layer quality. The laser cladding process is meaningful to quantitatively reveal the mechanism of single-channel multilayer cladding and forming under different laser heat source working modes. In this paper, a multi-field coupled 3D numerical model of the single-channel multilayer cladding process under diverse laser working modes is proposed, and the thermal physical parameters of the cladding material are computed on the basis of CALPHAD method. The mechanism of the impact of distinct working modes on the multi-field coupled ephemeral evolution process of laser cladding is investigated by using the solid/liquid interface tracking technique, which comprehensively considers the light-powder interaction between the powder waist beam and the laser beam in diverse working modes. The temperature, flow and stress fields are computationally solved for a single-channel multilayer cladding process. On the foundation of this study, the mechanism of the impact of pulse duty cycle and pulse frequency on the cladding behavior of single-channel and multi-layers during pulsed laser cladding was dissected. The macroscopic morphology and microstructure of the cladding layer were observed by KEYENCE VH-Z100R ultra-deep field electron microscope, and the feasibility of the model was confirmed. This study provides an important theoretical rationale for enhancing the cladding quality under different laser working modes.