Chaoyue Chen

Nozzle Mounting Method Optimization Based on Robot Kinematic Analysis

Nowadays, the application of industrial robots in thermal spray is gaining more and more importance. A desired coating quality depends on factors such as a balanced robot performance, a uniform scanning trajectory and stable parameters (e.g. nozzle speed, scanning step, spray angle, standoff distance). These factors also affect the mass and heat transfer as well as the coating formation. Thus, the kinematic optimization of all these aspects plays a key role in order to obtain an optimal coating quality. In this study, the robot performance was optimized from the aspect of nozzle mounting on the robot. An optimized nozzle mounting for a type F4 nozzle was designed, based on the conventional mounting method from the point of view of robot kinematics validated on a virtual robot. Robot kinematic parameters were obtained from the simulation by offline programming software and analyzed by statistical methods. The energy consumptions of different nozzle mounting methods were also compared. The results showed that it was possible to reasonably assign the amount of robot motion to each axis during the process, so achieving a constant nozzle speed. Thus, it is possible optimize robot performance and to economize robot energy.

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.

Cold-Sprayed Metal Coatings with Nanostructure

Cold spray is a solid-state coating deposition technology developed in the 1980s. In comparison with conventional thermal spray processes, cold spray can retain the original properties of feedstock, prevent the adverse influence on the underlying substrate materials, and produce very thick coatings. Coatings with nanostructure offer the potential for significant improvements in physical and mechanical properties as compared with conventional non-nanostructured coatings. Cold spray has also demonstrated great capability to produce coatings with nanostructure. This paper is aimed at providing a comprehensive overview of cold-sprayed metal coatings with nanostructure. A brief introduction of the cold spray technology is provided first. The nanocrystallization phenomenon in the conventional cold-sprayed metal coatings is then addressed. Thereafter, focus is switched to the microstructure and properties of the cold-sprayed nanocrystalline metal coatings, and the cold-sprayed nanomaterial-reinforced metal matrix composite (MMC) coatings. At the end, summary and future perspectives of the cold spray technology in producing metal coatings with nanostructure are concluded.