Optical method of on-line temperature monitoring on the melt surface in laser metal deposition technology

摘要

Experimental results of on-line monitoring of temperature on the surface of a melt of stainless steel 304 in laser metaldeposition technology with an inclined position of the sensor relative to the laser beam are presented. The additivesynthesis setup uses the heating of a coaxial flow of a gas-powder mixture in the field of focused laser radiation from afiber-optic ytterbium laser with a continuous power up to 400 W. To control the temperature on the surface of the melt, amultichannel pyrometer in the SWIR brightness pyrometer mode was used. The spatial resolution of the optical systemwas approximately 100 μm, and the speed of the sensors was at least 5 kHz. A multi-wave optical diagnostics method isproposed, including monitoring of laser radiation reflected from the melt surface. The features of optical diagnostics ofthe surface of the melt in the technology of laser metal deposition are given. The results of measuring the temporaltemperature behavior as a function of the scanning speed and the distance from the substrate to the laser focus arepresented. The spectrum of temperature pulsations T* during the formation of the track is calculated. It is shown that asthe scanning speed increases, the pulsation spectrum of T* shifts toward higher frequencies in proportion to the speed. Itis also shown that the temperature T* and the mass productivity of track formation increase with a change in the distancefrom the substrate to the laser focus from 10 to 11 mm, and also with an increase in the powder mass flow rate from 8.4g/min to 15.6 g/min.