Validation of computational fluid dynamics method through experimental investigation of the plasma spraying process

Abstract

Numerical modelling has emerged as a powerful predictive tool to enhance plasma sprayed coatings quality and process efficiency. In the present work, a comprehensive Computational Fluid Dynamics model of a gas heating inside a direct current arc plasma torch, is developed, using the simulation software Ansys Fluent. It is therefore sought to test its accuracy and limitations by comparing its predictions to actual data generated in the South African Nuclear Energy Corporation plasma spraying laboratory. In this regards, titanium powder of respective size distributions, 0-63 μm, and 63-75 μm, is sprayed onto a metal piece work. The transport medium is an argon-nitrogen plasma jet, generated from a direct current torch running under an induced power of 12.8 – 13.1 kW. The spraying distance and powder carrier gas flow rate are varied throughout the experiment, from 75 to 85 mm, and 3.9 to 5.8 kg/h, respectively. Comparison of laboratory and simulation-based results were mostly in agreement, in terms of the plasma jet shape, the effect of power increase on the torch exit temperature, the effects of particle size distribution, and carrier gas variation on particle melting and trajectory.