Influence of substrate hardness on deposition behavior of single porous WC-12Co particle in cold spraying

Deposition of a dense coating with solid particles by cold spraying requires sufficient deformation of impacting particles and previously deposited underlying particles. The cermet particles and subsequent coating with a high hardness are difficult to deform upon impact. To increase the ability of deformation, the cermet spray particles with a porous structure are used to fulfill the requirements of deformation on impact. To understand the deposition mechanism, the deposition behaviors of single WC-Co spray particles impacting on the substrates with different hardness during cold spraying were examined using WC-12Co powders with different porosities. The substrates with different hardness including stainless steel, nickel-based self-fluxing alloy coatings were employed to examine the effect of substrate deformation on the cermet particle deposition. It was found that the WC-Co cermet particles with the porosities of 30% and 44% could be deposited on the substrate of different hardness from 200 to 800 kgf/mm2. The deposition of the particles is mainly attributed to the deformation of powders themselves. The properly designed porous cermet powder with certain hardness is necessary to deposit hard WC-Co cermet coating.