Computational and experimental study on laser heating of a Ni-based metal alloy

Both computational and experimental studies were conducted to characterize complex heat transport and damage evolution phenomena in a metal alloy material subjected to laser irradiation. A Ni-based alloy, Inconel 718, was subjected to various irradiances of a flat-top, 4 cm diameter beam of continuous wave, 1.07 μm wavelength light. In this numerical study, a nonlinear transient finite element (FE) analysis, based on conductive, convective and radiative heat transfer, was conducted to predict temperature evolution (i.e., during heating, melting, and cooling conditions), damage initiation, and damage progression. A two-dimensional axisymmetric model was built with experimentally relevant plate geometry. ANSYS, a commercial FE software package, was used to conduct the nonlinear transient analyses. Such analyses employ an element removal feature to predict realistic evolution of the melt front within the laser heated Inconel 718 plates. The element removal scheme ensured that the laser energy supplied to removed elements no longer contributed to heating the rest of the intact material portion, and that the melt elements would not reappear (e.g., during cooling stage). Spanning a wide range of laser irradiance levels (i.e., from 11 W/cm2 to 828 W/cm2), the numerical model demonstrated good agreement with the experimentally measured temperatures during heating and cooling. After confirming the validity of measured temperature progression, the numerical model provided predictions in good agreement with experimentally measured penetration times and final damage (hole) sizes.