Mechanistic Study Of The Deposition Process Of Cold Sprayed Copper Coatings On Polyetheretherketone Surfaces

Cold spraying is receiving increasing attention as a method of metallising polymer surfaces.In the few existing papers on cold spray metallisation of polymers,although metallic coatings have been successfully prepared on the surface of PEEK matrix polymers,the research is currently only at the experimental stage.A very important reason for this is that the mechanism of metal deposition on polymer substrates is not yet fully understood.Although ideal coatings were obtained in the experiments,the role of the individual parameters in controlling the deposition efficiency cannot be accurately deduced from the experiments.The aim of this paper is to investigate the deposition behaviour of copper particles on a PEEK substrate by cold spray metallisation through numerical simulations,to discuss the mechanism of thermal softening and melting of the substrate during the cold spray copper coating of PEEK,and to investigate the deposition mechanism of the coating using numerical simulations combined with experimental analysis.The main studies are as follows:(1)A three-dimensional CFD model of the flow field inside and outside the cold sprayed Laval nozzle and the substrate is developed to calculate the gas flow and particle motion of the nozzle at constant process parameters.A slip mesh model is used to simulate the heat transfer between the high temperature airflow inside the nozzle and the substrate wall surface in the transient calculation and the calculated substrate surface temperature is used as the initial substrate temperature in the subsequent numerical simulation of particle deposition.(2)A modified Johnson-Cook material model of PEEK was embedded in ABAQUS using the VUMAT user subroutine and a CEL 3D finite element model was built to simulate the deposition of copper metal particles on the surface of the PEEK substrate.The PEEK substrate is adiabatically compressed by the high velocity impact of the copper particles and pushes the compressed material into the lateral regions of the particles resulting in a large plastic deformation,leading to a rapid increase in temperature in the lateral regions due to the large plastic deformation and exceeding the melting point.(3)In this paper,a random multi-particle model is generated with the aid of a Python script that specifies the position of the particles according to their particle size distribution.The bonding morphology of the copper-metal coating to the substrate and the accumulation of thermal effects on the substrate surface affected by impact are investigated and the results of comparative tests reveal that the bonding mechanism between the copper-metal coating and the PEEK polymer is mechanical interlocking.The work in this paper systematically investigates the mechanics of the deposition process of cold sprayed copper coatings on PEEK surfaces,laying the foundation for the practical application of cold sprayed metal coatings on different types of polymers.