Study Of HVOF Bonding Mechanism Based On Explosive Welding Theory

High Velocity Oxy-Fuel(HVOF) Spraying has a lot in common with Explosive Welding(EXW) process. Those two methods are both conducted with high velocity and severe reaction to combine same or different kinds of materials. Jet phenomenon can be observed during both HVOF and EXW process which results in high bonding strength between two materials. In this paper, HVOF spraying particles bonding mechanism is investigated on the basis of EXW bonding theory.In order to investigate the mechanism of particles' deposition on substrate, samples of substrate with different kinds of materials(Al, Cu, Steel) deposited with individual particle were processed, by the HVOF spraying system, invented and developed by Tianjin University. Use Scanning electron microscopy(SEM) to observe and analyze the morphology of deposited particles on the substrate, seeking to find out impacting and depositing mechanism of particles. On the other hand, with the help of ANSYS/LS-DYNA software, simulate the impacting process between substrate and particles with various temperatures and speeds, under different impacting conditions, trying to find out key influence to particle depositing behavior.By simulating the impacting process of particles, it is observed that there is metal jetting occurred when particle deposited on substrate with high velocity. With the substrate metal getting harder, its plastic deformation is getting less, while the deformation of particle increased obviously. Under the action of metal jetting near the contacting interface between two particles and substrate, fresh metal is exposed on the surface. Fresh surface and intimate contact result in successful bonding between particle and substrate. It's also indicated that the maximum effective plastic deformation happened near the contacting interface between particles and substrate. The bottom of particle deformed severely while the top part remained undeformed.Plastic deformation of particles and substrate is of crucial influence on bonding behavior of particle. Successful bonding requires moderate plastic deformation in both particle and substrate. The deformation is the result of interaction between particle and substrate during impacting; meanwhile it affects the metal jetting movements, which directly leads to bonding effect of particle.Only with appropriate plastic deformation on both sides of the contacting interface, can the particle and the substrate combine successfully.