Novel Fe-based and HVAF-sprayed coating systems for large area applications

In paper-machines, components such as dryer cylinders are often exposed to a combined load of wear and corrosion and, therefore, require an adequate surface protection. A high thermal conductivity of these coatings is desired, to increase the overall thermal efficiency. In this study, a novel high velocity air-fuel- (HVAF-) sprayed FeCrB/WC-Co coating is compared to an industrially established sealed FeCrBMn coating applied by wire-arc-spraying (WAS) in terms of wear behaviour of aged samples and thermal conductivity. The chosen feedstock material had powder fractions of -32 +11 mu m and -20 +3 and were applied with a powder feed rate of (m) over dot = 200 g/min by means of HVAF. A high powder feed rate and fine powder fractions were considered to reduce the required time to coat large areas and to reduce the post-processing effort. The samples were aged in saturated NaCl-solution steam at a temperature of T = 105 degrees C for t = 100 h. For the aged HVAF samples, a low influence of the aging on the wear rate was observed for both powder fractions. In contrast, for the aged WAS reference coating, a noticeable higher wear rate was measured. The thermal conductivity of the HVAF-sprayed coatings is significantly influenced by the employed powder fraction.