The effect of pulsed laser welding on hot cracking susceptible region size and weld pool internal geometry of Inconel 718: Numerical and experimental approaches

Abstract

A 3D finite-element thermal model has been developed to estimate weld geometry and analyze thermal gradients and cooling rates in pulsed laser welding of Inconel 718 superalloy. Since Inconel 718 superalloy is sensitive to hot cracking, the extent of hot crack sensitive areas including heat affected zone, mushy zone and partially melted zone is very important in the investigation of weldability for this alloy. Because the welding process is very fast and the welding width is very thin, the numerical modeling approach can be very helpful to overcome the difficulties and limitations of experimental procedure. In this study, a finite element model is presented to simulate the process of pulsed laser welding of Inconel 718 and to predict the temperature distribution and shape of the weld pool and finally to estimate the extent of the hot cracking sensitive regions. Heat source was modeled by the combination of conical Gaussian and ellipsoid Goldak. Then, the results of numerical model were compared to the experimental results at preheat temperatures of 308, 393, 473 Kelvin. The proposed numerical model exhibits good agreements with the experimental results including the internal and external weld pool geometries and the extent of the hot cracking susceptible regions. Furthermore, detailed pulsed temperature distribution and thermal cycle containing solidification latent heat are obtained. Accordingly, this pulsed temperature history is correlated to the internal and external geometry of pulsed solidified weld pool.