Investigation On The Deposition Behaviors Of HVOF Sprayed Particles On Substrate

In this paper, the deposition behavior of HVOF sprayed particles and substrate was investigated by adopting the combination of numerical simulation and experimental analysis method, which based on the excellent high bonding strength performance of coatings sprayed by HVOF. In order to explore effects of particle velocity, temperature, substrate preheating temperature and substrate material deformation ability on the particles deposition behavior, the impact models of Ni particles on the three substrates(aluminum, copper and stainless steel) were established and numerically analyzed by using ANSYS/LS-DYNA.Individual Ni60 particles were deposited experimentally onto non-preheated and preheated to 300℃ substrates(aluminum alloy, copper and stainless steel) by High Velocity Oxy-fuel(HVOF) spraying. Both the surface and the cross-sectional morphology of the particles were observed and analyzed by Scanning electron microscopy(SEM). From the viewpoint of energy to explore the cause of the high bonding strength between the particle and substrate, seeking to the parameter or method which could be used to predict the high bonding rate of particles. Through the study of the individual particle deposition behavior, try to understand the bonding mechanism from the view of energy and to guide the HVOF spraying process, and then lay the theory foundation for the prediction to the formation of coating and optimization of spraying process.Firstly, the impact processes of particles on substrates were simulated by numerical simulation software ANSYS/LS-DYNA. It is indicated that both particle and substrate exhibit moderate plastic deformation, and the increase of adiabatic shear instability jet(ASI) can be found with the increase of particle velocity. The maximum effective plastic deformation(Max-PEEQ) is concentrated at the surrounding of the contact interface, rather than the center point of impacting direction. With the increase of the particle temperature, particle effective plastic strain area increase, but the matrix deformation change is not obvious. Substrate preheating is helpful to improve the particle deposition efficiency and bonding ratio. The deposition efficiency of Ni/A6061 impact combination is highest, but the bonding ratio of Ni/Cu impact combination is the largest.Secondly, with the increase of the particle velocity, initial kinetic energy Ek, energy dissipated to the particle Ep and energy dissipated to the substrate Esub all monotonically increase for Ni/A6061, Ni/Cu and Ni/SS304 combinations. Energy distribution coefficient K was introduced to represent distribution proportion of initial kinetic energy EK between the particle and substrate. As particle velocity increasing, K value decreased firstly and then almost kept constant. When the particle velocity over 400 m/s, the K values for Ni/A6061, Ni/Cu and Ni/SS304 combinations were approximated to 4, 0.4 and 0.1, respectively.Finally,the contact between Ni particles and the three substrates was not perfect. The flattening ratio and compression ratio of the particle impacted on SS304 substrate was the largest, while those of the particles impacted on A6061 substrate was the lowest. The bonding ratio for Ni/Cu combination was 55.41%, larger than those for Ni/A6061(40.78%) and Ni/SS304(32.70%) combinations. Moderate K value was beneficial for interface bonding between particle and substrate. One could obtain enhanced interface bonding by optimizing K value during coating spraying.