NUMERICAL ANALYSIS OF GAS-DYNAMICAL AND MECHANICAL OXIDATION PROTECTION AGAINST OF THE HEAT-AFFECTED ZONE DURING COAXIAL LASER CLADDING

Results of investigations into the dynamics of inert-gas jets formed by a triple coaxial nozzle in the region of interaction of laser radiation with the treated material in laser cladding have been presented. An analysis has been made of the mechanisms of admixing of the oxygen from the surrounding air medium to the jet of protective inert gas above the heat-aff ected zone (HAZ) on a part′s surface. It has been shown by calculation that the mass fraction of the oxygen above the HAZ is very high, which may result in the oxidation of the metal surface. Schemes of use of a protective screen, insulating mechanically the inert-gas jets and the region of their interaction with the treated part from the environment have been proposed. Results of numerical investigations into the character of gasdynamic fl ows for the proposed schemes of mechanical protection have been presented. When the protective screen is installed, the oxygen concentration near the treated surface of the product decreases by several orders of magnitude, which prevents the oxidation of the metal in the HAZ because of the action of laser radiation in wide limits of variation in the regime parameters of cladding. Distinctive features and the quality of oxidation protection of mechanical surfaces in laser processing of plane and cylindrical long-dimensional products have been discussed.
   
Author:  D. V. Bedenko, O. B. Kovalev
Keywords:  numerical modeling, gas dynamics, mixture of gases, oxidation protection, turbulence, laser cladding, coaxial nozzle
Page:  1259