Effect of thermal energy on the deposition behaviour, wear and corrosion resistance of cold sprayed Ni-WC cermet coatings

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Cold spraying is emerging as one of the versatile coating techniques applicable in vast variety of applications ranging from overlay coatings to structural repairs. Though variety of metals and their alloys have been successfully deposited using this technique, deposition of cermet with high volume percentage of carbide particulates is still challenging. Existing reports reveal that the deposition of cermet coatings was obtained from blend of metal (binder) and ceramic (particulates) powders. Understanding the deposition behaviour of commercially available cemented carbide in cold spraying has technical significance since these cermets have huge industrial potential to protect components from wear and corrosion. Deposition of cermet using cold spray has a challenge since increase in particle velocity not only increases the plastic deformability of binder phase but also reduces the particulate phase in coatings since the supersonic velocity leads to fracturing and shattering of particulates. State of binder and particulate in the feedstock plays a crucial role in successful deposition. In this work, two different Ni-WC cemented carbides were deposited and comprehensively characterized for inter-splat bonding state and powder state and the same is correlated with the mechanical and corrosion performances of the coatings. The role of thermal energy in the coating formation is studied and discussed in detail. Along with a proper feedstock, engineered nozzle design to enhance the thermal energy input to the feedstock is required to obtain dense cemented carbide coatings with high particulate retainment.