Direct Current Plasma Spraying: Diagnostics and Process Simulation

Abstract This paper presents our current knowledge in direct current (d.c.) plasma spraying with conventional stick‐type cathode plasma torches. It deals with the experimental methods and models used to better understand and /or control the characteristics of plasma jet, particles in‐flight and at impact. The first part refers to measurements and on‐line monitoring or control. The emphasis is on (i) the effect of arc root fluctuations and electrode wear on particle treatment and coating formation; (ii) the drastic importance of the interface between the flattening particles and substrate. The second part examines the models used to predict gas flow field and particle parameter distributions at impact. It presents: (i) steady and 2‐D models that allow optimal experimental design with a limited number of experiments as well as education and training; (ii) 3‐D and time dependent models that make it possible to take account of the arc root fluctuation at the anode and a stochastic and time‐dependent particle injection description.