Temperature distribution of gas powder jet formed by coaxial nozzle in laser metal deposition

Results of the experimental study of the effect of the laser radiation on the jet of a gas-powder mixture are presented. The flow of the gas-powder mixture (GPM) was formed by the cone-slit nozzle of the set-up of laser metal deposition (LMD). Spatial-temporal distributions of the temperature of the powder phase of the GPM are obtained. Three granulometric compositions of stainless-steel powder Ch18N9 (PR-X18H9) was used apart in the experiment. The weight-average diameters d50 of powder particles of their compositions were 114, 63 and 36 μm, respectively. The characteristic distance of the temperature rise of particles in the gas-powder jet and the maximum temperature of particles are obtained experimentally and amount, respectively: 9.4 mm and 2200 K for the coarse powder; 6.3 mm and 2250 K for the medium-sized powder; 4.6 mm and 2700 K for the fine powder. The heating rate increased from 0.4*10^6 K/s for the coarse powder to 0.68*10^6 K/s for fine powder. The results of the study can be used to develop methods and tools for monitoring and control the LMD process. The revealed features of the dynamics of the temperature of the powder phase in the LMD process must be taken into account in modeling the processes of the effect of laser radiation on a gas-powder medium.