Effects of surface melting particles on adhesion of cermet coatings by high velocity oxy-fuel spraying

The conglomerate structure of surface melting particles, in which the metallic out-layer of refractory particles (WC, SiC, TiC, etc.) are melted during spray process, is formed by using high velocity oxy-fuel(HVOF) spraying. The effect of solid-liquid two-phase structure on the adhesive behavior of HVOF coatings is investigated. It is found that the adhesive strength of HVOF coating is positively related to the density and volume fraction of solid phase in sprayed particles. Two parameters to characterize the two-phase structure in HVOF spraying are proposed by taking the density, volume fraction, and velocity of solid particles into account. The two parameters are named the effective mass factor of solid phase and the factor of effective kinetic energy of solid phase, respectively. The former is defined as the product of density and square of volume fraction of solid particles, and the latter is the product of the one and square of particle velocity. The correlation between the parameters and adhesive strength of the coating shows that the adhesive strength increases with the increase in the effective kinetic energy of solid particles.