Effect of Coating Thickness on the Bond Strength of Cold-Sprayed Ni-Based cBN Coating on 42CrMo Substrate

Cold spraying has been applied to the fabrication of grinding wheels with a high production efficiency and small thermal effects. The thickness of the grinding layer is required to reach a certain value, and the bond strength can be satisfied for grinding wheels fabricated via cold spraying. A low bond strength causes the coating to peel off or cracks to appear along the coating-substrate interface. However, there have been few reported studies on the effect of the coating thickness on the bond strength between the coating and the substrate. Herein, the temperature difference between coating and substrate was proposed to elucidate the bond strength as a function of the coating thickness during cold spraying. On 42CrMo substrates, Ni-based cBN coatings with various thicknesses were deposited. A semiempirical analytical model was proposed to solve the temperature difference in the coating/substrate. The bond strength of the cold-sprayed Ni-based cBN coating first decreased and then slightly increased with increasing coating thickness, as opposite to the temperature difference. This study highlighted the linear negative correlation between the temperature difference and the bond strength. The effect of the coating thickness on the bond strength can be predicted by analyzing the temperature difference in the coating/substrate.