Real Time Cr Measurement Using Optical Emission Spectroscopy During Direct Metal Deposition Process

Real-time chromium composition analysis during direct metal deposition of pure chromium and H13 tool steel materials was performed using optical emission spectroscopy of the laser-induced plasma. Four second-order polynomial calibration curves were constructed using spectral line intensity ratios between two neutral chromium lines and two neutral iron lines. Second-order polynomial calibration curves were also formed using plasma temperature and electron density. The plasma temperature was obtained using Boltzmann plot of nine neutral iron lines between 370 nm and 390 nm. The electron density was estimated using Stark broadening of Fe-I line at 426.047 nm. Chromium concentration in the range from 10% to 60% was measured using these calibration curves in real-time during synthesis process and verified from energy dispersive X-ray spectroscopy of the manufactured parts. The measurement from line intensity ratio calibration curve is more accurate and has less standard deviation than that from plasma temperature and electron density calibration curves. The accuracy of the measured chromium concentration is within 2.78% in at.% and the average resolution of the measurement is around 5.12% in at.% from the averaged values of four line intensity ratio calibration curves.