Abstract
A two-dimensional thermal elasto-plastic numerical model is developed by finite element method to analyze and compare the mechanical driving factor for heat affected zone (HAZ) liquation cracking during laser welding and hybrid laser-arc welding techniques. Calculations of transient temperatures and cooling rates are used in conjunction with solidification theory to analyze weld pool characteristics during weld-metal solidification. The model is successfully verified by comparing calculated and experimental weld bead geometry and secondary dendrite arm spacing within the weld solidification microstructure. Computational analyses by the model provide valuable insights both into the influence of welding parameters on thermally induced strain rate gradient, which influences cracking, and possible reduced HAZ cracking tendency with the application of hybrid laser-arc welding compared to ordinary laser beam welding.
Highlights
Precipitation strengthened nickel-base superalloys are extensively used in hot sections of aero engines and land-based power generation gas turbines, due to their excellent elevated temperature mechanical properties and resistance to hot corrosion
A two-dimensional thermal elasto-plastic numerical model is developed by finite element method to analyze and compare the mechanical driving factor for heat affected zone (HAZ) liquation cracking during laser welding and hybrid laser-arc welding techniques
A numerical model is developed to study the mechanical driving factor for HAZ liquation cracking during laser and hybrid laser-arc welding processes
Summary
Precipitation strengthened nickel-base superalloys are extensively used in hot sections of aero engines and land-based power generation gas turbines, due to their excellent elevated temperature mechanical properties and resistance to hot corrosion. Welding is a desirable economical and versatile technique for joining nickel-base superalloys both during fabrication as well as to repair damaged sections. Even though hybrid laser-arc welding offers a number of advantages over conventional welding, application of the joining technique to nickel-base superalloys in lieu of laser welding requires adequate understanding and comparison of cracking tendency during the two joining methods. This is the motivation for this research, which was initiated with the primary objective to develop a numerical model to analyze and compare thermally-induced strain rate and its dependency on process parameters during laser and hybrid laser-arc welding techniques. The model description and the results of the study are reported and discussed in this paper
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