Universal Law of Maximum Particle Velocity as a Function of Particle Diameter and Density in HVOF Thermal Spray Process

Abstract

This paper investigates a universal law of the maximum particle velocity as a function of the particle diameter and material density in high-velocity oxy-fuel (HVOF) thermal spray process. The universal law is proposed based on the theoretical considerations of the equation of particle motion. The ranges of diameter and material density of the spray particles selected in this paper are 10-60μm and 4,000-16,000 kg/m³. This series of the maximum particle velocity obtained by the universal law were compared with the results obtained by one-dimensional calculation of the gas/particle flows, with the equivalence ratio of the HVOF thermal spray gun to be 0.5, 1.0 and 1.5. The present research revealed that 1) The maximum particle velocity follows simple Eqs. (10) and (12) within the accuracy of ±4%, 2) Equation (12) provides the relative maximum particle velocity for an arbitrary set of material diameter and density, against a maximum particle velocity for another set of reference particle diameter and density, 3) Equations (10) and (12) holds within the range of particle diameter 10-60μm, and particle density 6,000-16,000 kg/m³. They correspond to the Stokes number, St, to be around 7 < St < 100.