In order to control the arrangement of additive materials in the thermal spray coating, this work devised a new thermal spraying method that fuse of HVOF and punching. In the devised method, a foil-like material is placed on the line of path of the HVOF, and the ejected particles are used to punch out the foil and transport the punched foil pieces to the substrate. Thereby forming a laminated structure composed of the ejected particles and the foil-like material. First, in order to evaluate the feasibility of the devised method, a conditional expression for the sprayed particles to punch out the foil-like material was derived using the calculation formula of the required load in the punching process. Next, in order to evaluate the validity of this conditional expression, a 3D model of one particle given initial velocity was created, and performed CAE analysis. The feasibility of the devised method was confirmed by CAE analysis. Subsequently, as a demonstration experiment, fixed-point thermal spraying using aluminum bronze and aluminum foil was performed, and it was confirmed that the foil could be punched out and added to the coating with ejected particles. By SEM and EDX of the cross section of the film, it was confirmed that a laminated structure was formed in which the ejected particles placed the upper and the incorporated foil placed the lower.

View full abstract

There are few methods available to monitor the occurrence of micro-defects inside the material during thermal spraying and additive manufacturing. In this study, process monitoring of both processes by using originally developed acoustic emission (AE) measurement system that can be used in high noise environments. Wireless version of this AE measurement system is also available and it can be easily installed in real industrial scenes. The detected AE events were located and compared with the process logs and post-processing observations, and it was found that the AE events were caused by the occurrence of micro-defects during the process. It is useful for optimizing process conditions, detecting process abnormalities, and clarifying the mechanism of micro-defects during the processes.

View full abstract