Calculation of parameters of particles in a plasma jet and modeling of kinematic modes of spraying of wear resistant material

In this article the calculations on the strength of the coupling halves of the CV joint by the finite element method in the system of APM FEM. This calculation method is a method of creating a mathematical model and method of investigation. The assigned technological parameters of plasma spraying, namely, the estimated capacity of the plasma generator is 50 kW, and reach air temperature at the output of 3000 K, and the corresponding enthalpy of 3.8·106 j/kgK. Based on the analysis of the wear of the contact surfaces of the coupling halves, and also carried out strength calculations, was chosen as the material for plasma spraying – tungsten carbide. Developed mathematical model to determine the temperature of the powder particles and their velocities in a plasma jet. Based on the earlier dependence of the kinematic regimes of plasma spraying, the resulting system of equations for the kinematic modes that enable you to organize control of the kinematics of the deposition process details with the internal spherical surface.


Introduction
Today, there are a large number of chemical, galvanic and physical methods for applying wearresistant, heat-resistant, corrosion-resistant and other coatings that enhance the performance properties of the surfaces. A detailed analysis of a particular method or method in a scientific article is impossible, so it was decided to choose a promising area to establish reliable, durable and wearresistant coatings, namely, plasma spraying [1,2].
The aim of this work is the simulation of mathematical model calculate the velocity and temperature of the composite powder in the stream of the air plasma. The output of the system of equations for the kinematic modes of plasma spraying to the inner spherical surface of the coupling half.

Materials and methods of research
As a parts representative for coating was chosen as the spherical coupling of the hinge of equal angular speeds, the 3D model of which is shown in Fig. 1. To confirm and verify the appropriateness of applying a plasma spray coating on the inner spherical surface of the half couplings, were calculated by the finite element method in the system stress analysis APM FEM program KOMPAS-3D V15.1. This calculation method is a method of creating a mathematical model and method of investigation.
amodel coupling half; bfinite element mesh; vthe total linear displacement; gfactor of safety for strength; dsafety factor for yield strength To solve this problem it is necessary to determine the change similar parameters for the plasma jet created in a plasma torch. The estimated capacity of the plasma generator is 50 kW. Achieved temperature at the output of 3000 K. The Corresponding enthalpy of 3.8•106 j/kgK [3]. The thermal efficiency of the plasmatron 70 %. Air flow of plasma-forming G = 9 g/s.
The choice of material of the deposition surface of parts produced with the help of table 1, which presents a selection of materials functional coatings [4]. Electrical isolation Based on the analysis of the main types of wear undergone by the inner spherical surface of the coupling hub, was selected as the sprayed material is tungsten carbide.

The study and results
The speed of the sprayed particles is the subject of experimental study. Therefore, to compare data obtained from different researchers in this field, it is not possible because the experiments were carried out on different equipment and under certain laboratory conditions. In this regard, we propose a mathematical approach to determination of the velocity of sprayed particles.
Modeling the motion of particles of tungsten carbide powder in a plasma jet is taken that the tungsten carbide is spherical in shape.
Determining the temperature of the sprayed particles in plasma spraying should be carried out with the radius of the particles and changes in material properties along the radius.
Heating of the particles of the powder material of tungsten carbide was seen in the assumption of their spherical shape, which is justified by the micron size of particles and their rotation due to asymmetrical entry of the powder into the plasma jet.
The temperature of the sprayed particles was found from the equation of heat transfer of powder particles with the gas. After mathematical modelling of process of heating the tungsten carbide powder, was obtained the equation for the temperature of sprayed particles: Knowing that reach the temperature output of 3000K, and the melting point of tungsten carbide 3143К, then deal with the case when the particles are two-phase state, that is composed of two layers: the inner (solid) and outer (liquid). As further heat supply boundary melting is shifted inwards. In the end, during the deposition of tungsten carbide on the surface of the solid layer in the form of tungsten particles settle to the bottom border of the sprayed layer due to its density and phase state, and the carbon and all related impurities and gases rise to the upper level of the sprayed layer (carbon glass).
where vthe speed of the sprayer relative to the surface, ψthe angle between the tangent and forming a body of revolution at the current point and the axis z; βthe pitch of the spiral path of the spot deposition on the surface; nthe number of revolutions of the main drive; sthe reverse flow. It should be noted that the cylindrical z coordinate for the spherical surface of the half-coupling is expressed by the equation [7]: The number of revolutions of the main drive is given by: 2. Based on the earlier dependence of the kinematic regimes of plasma spraying, the resulting system of equations for the kinematic modes that will allow to systematize the management of the kinematics of the deposition process details with internal spherical surface.