Development of HVAF-sprayed novel Fe-basedcoatings for large area applications

The use of novel Fe-based feedstock materials in corrosion and wear protection coatings constitutes an important trend in thermal spraying. A typical field of application for such protection coatings are rotary dryers of paper machines. At the moment, these cylinders are coated either by wire arc spraying (WAS) or less frequently by high velocity oxygen-fuel (HVOF). A disadvantage of WAS coatings is their high thickness, which has a heat-insulation effect, and their high roughness. Therefore, time-consuming post production grinding is necessary in order to achieve the required surface roughness. The goal of this study is to develop high velocity air-fuel (HVAF-) process parameters that enable the production of a thin, dense and near net shape Fe-based corrosion/wear protection coating system. For this purpose, the HVAF-process and a FeCrB/WC-Co feedstock material were investigated. In a first step, the influence of the spraying distance l and the powder feed rate f on the microstructure of the resulting coatings was investigated by means of light microscopy. Furthermore, the wear and corrosion behaviour of the developed coating system was analysed. The results show that dense and crack-free coatings can be produced by means of HVAF-spraying using a FeCrB/WC-Co feedstock material.