Particle behavior of nanocrystalline 316-stainless steel during high velocity oxy-fuel thermal spray

Abstract The present paper investigates the particle behavior of nanocrystalline 316-stainless steel powders during high velocity oxy-fuel (HVOF) spray. The feedstock powders were synthesized by mechanical milling to produce flake-shaped agglomerates with an average grain size of less than 50 nm. The powders were then introduced into the HVOF spray to produce a nanocrystalline coating. A mathematical model is developed to study the variation of different agglomerate sizes resulting from the mechanical milling process on the particle behavior during thermal spraying. A generalized Newtonian equation describing the momentum transfer was used, which incorporates a geometric ratio to account for the size and morphological variations of the micron-sized agglomerates with nano-grained structure. Particle velocity from the numerical calculations indicated that the velocity profile depends strongly on the thickness of the particles, which is a function of milling time and milling media .