Fig. 1. Plasma monitoring platform for laser additive manufacturing

Fig. 2. Image processing of porosity defect

Fig. 3. Comparison of metal plasma plume and ceramic plasma plume (P=340 W). (a) Metal plume; (b) ceramic plume

Fig. 4. Spectrum of plasma produced by alumina ceramic laser additive manufacturing. (a) Characteristic spectrum (P=480 W); (b) Al Ⅱ 422.74 nm spectrum time domain variation (P=690 W)

Fig. 5. Relationship between different process parameters and plasma line intensity. (a) Relationship between laser power and spectral line intensity; (b) relationship between scanning speed and spectral line intensity; (c) relationship between powder flow rate and spectral line intensity

Fig. 6. Relationship between different process parameters and plasma electron density.(a) Relationship between laser power and electron density; (b) relationship between scanning speed and electron density; (c) relationship between powder flow rate and electron density

Fig. 7. Pores in single layer thin-walled parts. (a) Interlayer pores and intralayer pores; (b) shrinkage cavity

Fig. 8. Relationship between plasma characteristics and porosity defect. (a) Relationship between spectral strength and porosity; (b) relationship between electronic density and porosity

Fig. 9. Macro cracks on the surface of the parts. (a) Single track single-layer parts; (b) single track multi-layer parts

Fig. 10. Relationship between plasma characteristics and crack number. (a) Relationship between line strength and crack number;(b) relationship between electron density and crack number