Study on the Growth of Holes in Cold Spraying via Numerical Simulation and Experimental Methods

Guosheng Huang,Hongren Wang,Lukuo Xing,Xiangbo Li

doi:10.3390/coatings7010002

Abstract

Cold spraying is a promising method for rapid prototyping due to its high deposition efficiency and high-quality bonding characteristic. However, many researchers have noticed that holes cannot be replenished and will grow larger and larger once formed, which will significantly decrease the deposition efficiency. No work has yet been done on this problem. In this paper, a computational simulation method was used to investigate the origins of these holes and the reasons for their growth. A thick copper coating was deposited around the pre-drilled, micro-size holes using a cold spraying method on copper substrate to verify the simulation results. The results indicate that the deposition efficiency inside the hole decreases as the hole become deeper and narrower. The repellant force between the particles perpendicular to the impaction direction will lead to porosity if the particles are too close. There is a much lower flattening ratio for successive particles if they are too close at the same location, because the momentum energy contributes to the former particle’s deformation. There is a high probability that the above two phenomena, resulting from high powder-feeding rate, will form the original hole, which will grow larger and larger once it is formed. It is very important to control the powder feeding rate, but the upper limit is yet to be determined by further simulation and experimental investigation.

Highlights

Cold spraying, called cold gas dynamic spraying or kinetic spraying, was discovered by accident in a wind tunnel experiment [1]
The development of new material systems with enhanced properties covering a wide range of required functionalities of surfaces and interfaces, from internal combustion engines to biotechnology, has brought forth new opportunities for cold spraying with a rich variety of material combinations [3]
It has some disadvantages at low processing temperatures, such as low ductility and absence of self-replenishing, which will strongly affect the efficiency of cold spraying, reduce

Summary

Introduction

Called cold gas dynamic spraying or kinetic spraying, was discovered by accident in a wind tunnel experiment [1] They found that a metal particle will adhere to substrate when the particle exceeds a certain velocity, called the critical velocity. Cold spraying is capable of repairing copper, aluminum, titanium metal and their composite structures [4,5], including enhancing aluminum surfaces with copper and titanium coating. It has some disadvantages at low processing temperatures, such as low ductility and absence of self-replenishing, which will strongly affect the efficiency of cold spraying, reduce

Methods

Discussion

Conclusion