Acoustic emission signal characteristics of crack and porosity defects formation during laser cladding WC/Fe313 coatings

The addition of WC particles during metal laser cladding (LC) additive manufacturing process not only increases the high-temperature wear resistance but also improves the cracking sensitivity of the cladding. In this paper, LC processes of Fe313 power mixed with different contents of WC were monitored by an acoustic emission (AE) equipment. Combined with the results of temperature and morphology of molten pool and 3D micro-CT imaging results of defects in the cladding, the AE signal response characteristics (Amplitude distributions, $A{E}_{RMS}$ and $A{E}_{ASL}$ of AE hit signals and time-frequency decomposition results of AE waveform signals) of crack and pore defects during LC process were obtained. The crack formation time detected by the AE signal was consistent with the monitoring results of the high-speed camera. Furthermore, the number and type of defects monitored by the AE signal were consistent with the results of CT imaging and microscopic analysis. The results indicated that the AE monitoring was a reliable online detection method for LC process. Based on the CT imaging results, the unmelted WC particle in the CT image was separated, and the mass fraction of WC powder was calculated and identified, and the detection error of the mass fraction was only 0.505 %. This study can provide theoretical guidance for defect identification and feedback control in laser additive manufacturing process.