Yingchun Xie

Effect of substrate temperature on interfacial bonding for cold spray of Ni onto Cu

Cold spray as a relatively new surface modification technique has great potential in the industry due to its ‘low working temperature’. The bonding quality between the cold-sprayed coating and the target substrate is one of the most important evaluation index for the coating performance. In this study, the interfacial bonding features between cold-sprayed Ni coatings and Cu are investigated to clarify the role of substrate temperature in the coating–substrate bonding. The finite element analysis model which can simulate the heat conduction through the coating–substrate interface is developed to model the particle deposition process on the substrate. The surface morphology and cross section of the experimentally deposited particles are observed by scanning electron microscope. The substrate surface oxidization behavior and coating–substrate interfacial atomic mixture are evaluated through the energy-dispersive spectroscopy line scans. The results indicate that heat conduction from the high-temperature substrate plays an important role in heating the interfacial region. The increased interfacial temperature significantly enhances the metallurgical bonding by improving the coating–substrate atomic mixture at the interface. Besides, the high-temperature substrate is also found to result in prominent metal jet and strong mechanical interlock due to the enhanced thermal softening effect. As a consequence, coating mass and coating–substrate bonding strength are promoted by using the high-temperature substrate.

Effect of spray angle on Ni particle deposition behaviour in cold spray

ABSTRACT In this work, cold sprayed Ni particles depositing onto stainless steel (SS) and aluminium substrates was studied the deposition behaviour and bonding mechanism at different spray angles. Contrary to common investigation which is limited to the cross-section or surface, the fractured contact surface on deposited particle was obtained by detaching the as-sprayed particle from the substrate. The results show that the contact surface of Ni particle detached from Al substrate was smooth without signs of metallurgical bonding or interfacial remelting. Compared to the relatively hard SS substrate where dimple-like fractures were found, the substrate hardness is found to play an important role in the formation of metallurgical bonding. Additionally, finite element analysis results show that the relatively hard SS substrate leads to a higher maximum contact pressure, which can promote the formation of metallurgical bonding. It can be convinced that the high contact pressure area is the determining factor for metallurgical bonding.