Numerical and Experimental Characterisation of Melt Pool in Laser Powder Bed Fusion of Ss316l.

Abstract

Laser powder bed fusion (LPBF), also referred to as Selective Laser Melting (SLM), an additive manufacturing (AM) technology, holds significant potential for fabricating three-dimensional metallic components with complex structures. Due to the dynamic application of melting and cooling thermal cycles, maintaining an accurate surface quality and shape in LPBF is extremely challenging. Because the quality of the manufactured products is significantly dependent on the thermal behaviour and temperature distribution inside the melt pool, it is critical to investigate the melt pool's dynamic stability during the LPBF process. Consequently, a FEM model that has been experimentally validated can significantly assist in the precise characterisation of temperature distributions and melt pool dimensions. In this study, the macro-scale modelling approach has been adopted in which a transient model is constructed on a 3D moving Gaussian heat source with varying process variables such as scan velocity, laser power, laser beam radius, hatch spacing, number of layers, and scan angle for each layer in order to investigate their effect on melt pool shape in LPBF of SS316L powder. This research proposed a three-dimensional finite element model for predicting the temperature gradient and melt pool characteristics in the LPBF of SS316L. The method considers the laser penetration depth and its influence on the melt pool characteristics calculated in a multiple-layer (15) and multiple-track (6) FEM model with variable process parameters, i.e., laser power, scan speed, beam radius, and hatch spacing. Literature-based experimental data were utilised to calibrate the proposed heat source model, and the calibrated FEM model was then verified through experiments. The findings of the modelling demonstrated reasonable agreement with the experiments. The interlayer and intertrack effects were investigated. Each track's and layer`s temperature distribution and the melt pool's depth, width, and length were evaluated, and the measurements for each variable were analysed. The average melt pool length, width, and depth were found to have 1.88%, 1,49%, and 2.12% relative errors between the FEM model and experimentally measured dimensions for an optimal range of different process parameters.

Combining high-throughput imaging in visible and SWIR wavelengths for in-situ porosity prediction in laser powder bed fusion

“…13 These cameras can operate in different spectral ranges, such as visible or short-wave infrared (SWIR), and provide rich information about the temperature, shape, size, and dynamics of the molten pool, as well as the spatter, porosity, and surface roughness of the solidified part. 14 However, the raw images from the cameras are often noisy, distorted, and complex. They therefore require advanced feature extraction and machine learning techniques in order to collect meaningful and relevant information that can be used for quality assessment and control.…”