Investigation of Influence of Plasma Spraying Process Parameters on the Level of Residual Stresses

The method to determine thermal fields considering dependence of thermophysical and mechanical properties of coating materials and a base from the temperature, the running of plastic deformations and stresses relaxation at plasma spraying is suggested. The mathematical model of calculation of thermal field with moving boundary considering nonlinear feature of coating growth at layer-by-layer deposition and dependences from thermophysical properties of materials of the system «coating-base» is developed. The model application helps to estimate the effect of the parameters of plasma spraying process on the level of the residual stresses in the increased coatings.

Swirling Effects in Atmospheric Plasma Spraying Process: Experiments and Simulation

Experimental evidence of swirling effects in 3D trajectories of in-flight particles is presented based on static and dynamic footprints analysis as a function of stand-off distance of Al2O3 deposited employing a Metco-9MB torch. Swirling effects were validated with a proprietary computational fluid dynamics (CFD) code that considers an argon-hydrogen plasma stream, in-flight particles trajectories, both creating the spray cone, and particle impact to form a footprint on a fixed substrate located at different distances up to 120 mm. Static and dynamic footprints showed that swirl produces a slight deviation of individual particle trajectories and thus footprint rotation, which may affect coating characteristics.

The Influence of Technological Parameters of the Plasma Spraying Process on the Macrostructure of Titanium Coatings

Capillary-porous surfaces are used in endoprosthetics as well as in catalytic converters and heat exchangers to increase the strength of adhesive bonding. Plasma spraying is one of the methods to obtain rough coatings for capillary-porous surfaces. Determining the relationships between the parameters of macrostructure of capillary-porous surfaces and the technological factors of the plasma spraying process enables one to control the surface characteristics. It is an important and fundamental element in the formation of the required properties of the surface. However, studies on the influence of technological parameters of plasma spraying on the construction and macrostructure of plasma-sprayed titanium surfaces are insufficient in scientific literature. This paper presents a study on the influence of roughness, curvature and the material of the supporting plate surface, as well as distance and angle of spraying on the structure of a VT1-0 titanium capillary porous coating applied to a VT6 titanium alloy supporting plate. A regression analysis of the experiment results is performed. It is shown that all the parameters have a significant influence on the surface structure. The experimentally obtained relationships make it possible to produce surfaces with required macrostructure parameters. They help to evaluate the possibility of obtaining titanium surfaces of this kind and thoroughly select parameters of the plasma spraying process in order to obtain surfaces with the required properties.