Non-invasive optical characterization and estimation of Zn porosity in gas tungsten arc welding of Fe–Al joints using CR model and OES measurements

Abstract

In this study, we employed a non-invasive approach based on the collisional radiative (CR) model and optical emission spectroscopy (OES) measurements for the characterization of gas tungsten arc welding (GTAW) discharge and quantification of Zn-induced porosity during the GTAW process of Fe-Al joints. The OES measurements were recorded as a function of weld current, welding speed, and input waveform. The OES measurements revealed significant line emission from Zn-I in 460 nm to 640 nm and Ar-I in 680 nm to 800 nm wavelength range in all experimental settings. The OES cum CR model approach for Zn-I line emission enabled the simultaneous determination of both essential discharge parameters i.e. electron temperature and electron density. Further, these predictions were used to estimate the Zn-induced porosity using OES-Actinometry on Zn-I emission lines using Ar as actinometer gas. The OES-actinometry results were in good agreement with porosity data derived from an independent approach, i.e., X-ray radiography images. The current study shows that OES-based techniques can provide an efficient route for real-time monitoring of weld quality and estimate porosity during the GTAW process of dissimilar metal joints.