Special features of formation of plasma torch under conditions of hybrid laser-arc welding

This paper is devoted to analytical description of processes occurring in hybrid discharge plasma under conditions of laser-arc welding with deep melting. The axially symmetric boundary layer approximation is used to solve the problem on the outflow of a jet of hot metal vapor into an atmosphere of cold protective helium gas in view of the compressibility of gas mixture and of the bulk heat release during absorption of laser radiation in plasma. In so doing, the degree of ionization of plasma is determined from the solution of kinetic problem in the approximation of constant collision frequencies for a helium-iron mixture without the assumption of local thermal equilibrium. A series of experiments in the interferometry of plasma torch under conditions of pulsed laser stimulation of metal targets are performed to confirm the obtained results.