Abstract
Large-area applications, such as Yankee cylinders for paper machines, are often exposed to corrosion/wear, and therefore require adequate surface protection. The goal of this study is to develop a cost-efficient coating system that offers comparable protection to the industrially established Fe-based coating systems produced by wire arc spraying (WAS). Cost efficiency is to be achieved by using an economically priced, novel Fe-based feedstock material, the high velocity air-fuel (HVAF) process as well as a coating thickness reduction. In this study, the feedstock material FeCrB/WC-Co with the grain size fraction -32 +11 µm was investigated. Two coating thicknesses dct ≈ 120 µm and dct ≈ 240 µm and two different powder feed rates p = 40 g/min and p = 200 g/min were considered. An industrially established WAS FeCrBSiMnC coating system was used as reference. To examine the microstructure, cross sections of the coatings were prepared and investigated with a light microscope. Electro chemical polarization and pin-on-disc- (POD) tests were performed to investigate the corrosion and wear properties of these coating systems. Furthermore, XRD measurements were used to investigate the phase composition. The results show that a dense and crack-free coating can be produced with a powder feed rate of p = 200 g/min and that the powder feed rate p has a significant influence on the corrosion behaviour.
Highlights
In recent years, economical factors such as raw material and post-processing costs are playing an increasingly important role in the research of novel thermally sprayed wear and corrosion protection coatings
The goal of this study is to develop a cost-efficient coating system that offers comparable protection to the industrially established Fe-based coating systems produced by wire arc spraying (WAS)
The results show that a dense and crack-free coating can be produced with a powder feed rate of p = 200 g/min and that the powder feed rate p has a significant influence on the corrosion behaviour
Summary
Economical factors such as raw material and post-processing costs are playing an increasingly important role in the research of novel thermally sprayed wear and corrosion protection coatings. Wang et al showed that dense coatings with a low content of oxides can be produced with the HVAF process and explains this with the lower particle temperatures and the higher particle velocities compared to the HVOF process [4]. These results are confirmed by a number of studies [5 – 10]. The variety of different HVOF torch designs must not be neglected, which means that no general statement can be made about the oxygen content in the coatings applied by means of HVOF and HVAF spraying [13]
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