Investigation of low-pressure cold-gas dynamic spraying of polyamide-12 (PA12) on steel surfaces

Abstract

Due to their good tribological properties and corrosive resistance, thermoplastic coatings are becoming increasingly important in industrial applications. Thermal spray technologies in general and flame spraying in particular belong to the most common application methods. However, the high thermal energy inevitably leads to the risk of thermal decomposition, especially in the case of materials such as polyamide-12, which have a small discrepancy between the melting and degradation temperatures. Furthermore, flame-sprayed coatings often are highly porous, reducing its effectiveness as a corrosive barrier. As an alternative approach, polyamide-12 coatings were applied to steel substrates using a conventional low-pressure cold-gas dynamic spray system. Various mixtures including ceramic powders (Al2O3) as well as different injection concepts were investigated and evaluated. The focus was put on the resulting coating morphology. Furthermore, the cold-gas spraying system was modified with a continuous temperature control for the gas temperature to enable a more precise adjustment based on the melting temperature of the material in order to reduce the risk of thermal degradation.