Study On The Plasma Device Development For Metal Powders Preparation And Powders' Quality Performance Research

In recent years,"3D printing" have always been regarded as a synonym for Material Additive Manufacturing Technology.The development is now in the ascendant.With the wide application field and prospect,nevertheless,it also faces the problem of materials are single in type and poor compatibility.The lack of available powders material has become the bottleneck of large-scale industrial application,making this new technology is still like a flower in the mirror.Compared with the traditional industrial powders,Material Additive Manufacturing Technology made an additional request: powder grain size should less than 100 microns,particles should be solid spherical and achieve a certain proportion among each other.The distribution of the chemical elements of each powder particle is similar to the raw materials is necessary.These harsh requirements have become a challenge in many traditional methods.In this paper,we comprehensive analysis of these requirements.Based on the principle of arc welding,plasma cutting and aerodynamics.Then we innovatively use the plasma arc placed in the same direction to atomize the metal wires,with the "reverse-Laval tube" principle expansion nozzle to prepare spherical micron stainless steel,nickel base alloy,titanium alloy powders.The results of the study are as follows:(1)Single and multi-electrode plasma arc atomization,give full play to the plasma arc height temperature,high energy density and high aerodynamic advantages.More directly and quickly realize the melting and miniaturization of materials.(2)The expansion nozzle according to the characteristics of supersonic and subsonic plasma jet,Meanwhile,reverse application principle of rocket engine nozzle.Using Runge-Kutta method to solve the differential equation of energy and calculate a reasonable nozzle size.The velocity,temperature and pressure of the fluid passing through the Variable cross-section channel of the nozzle can be used to extend the cooling time of the material,and to accelerate the role of the plasma jet.The solidification of metal droplets is artificially divided into two transmission processes.(3)For the diameter of 4 to 10 mm filamentary material,the best soldering parameters are output current 90A-110 A,output gas pressure 0.40MPa-0.55 MPa,gas flow 35L/min-55L/min,and then the nozzle's minimum cross section radius 20.00 mm,the maximum radius of 29.02 mm,section 15 degree angle.The nozzle is located at the exit of the plasma jet at 70mm-75 mm.As a result,the shape of the prepared powder material is closer to the spherical shape and the appearance of the particles is present rapidly solidified.The average particle size was 57.96 mm and the particle size distribution was between 30?m-100?m,and the loose density of powder was 2.50g/cm3,and the tap density was about 2.72 g/cm3.