Investigation of the effect of welding current on morphology and microstructure of IN738LC alloy weld metal by GTAW method

Document Type : Research Article

Authors

1 Department of Materials and Metallurgical Engineering,, Amirkabir University of Technology, Tehran, Iran

2 Department of Materials and Metallurgical Eng., Amirkabir University of Technology, Tehran, Iran

Abstract

The distance of the secondary dendritic arms is an important microstructural feature in the dendritic solidification and has a great influence on the hardness of the alloy, and the main factor affecting it is the cooling rate. Due to the difficulty of its practical measurement, numerical methods should be used to predict it. In this study, first, 3 samples were produced with current of 95, 120 and 132. Then, using the results of the validated model, a 3D finite element model was developed to generate welding profiles and analyze transient heat transfer, and the cooling rate at different points of the weld metal was calculated. The model outputs (cooling rates, thermal gradient G and growth rate R) were used to describe the solidification structures. It was found that for the sample produced with current of 95 A, the cooling rate was between 650 K.S-1 to 800 K.S-1, but for the sample produced with a current of 132 A, the cooling rate was between 270 K.S-1 to 350 K.S-1. Then, using optical microscopy, the distance of the secondary dendritic arms in different regions was measured on the sample produced from the IN738LC superalloy, and the constants a and n in the mathematical relationship between the distance of the secondary dendritic arms and the cooling rate were obtained, which were equal to 34.62 and 0.3, respectively.

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Amirkabir Journal of Mechanical Engineering
Volume 56, Issue 12
In Progress
2025
Pages 1-1

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